From c178d8e97a412f27b39d9bcec290d657d5afd5d3 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Sun, 19 Apr 2026 13:44:03 +0300
Subject: [PATCH 01/50] MDEV-39368: Trace replay: add --extra-server support,
 part 1.

---
 client/mysqltest.cc                          | 366 ++++++++++++++++++-
 mariadb-plugin-columnstore.install.generated |   2 +
 mysql-test/EXTRA_SERVER_QUICKSTART.txt       |  89 +++++
 mysql-test/include/start_extra_server.inc    | 105 ++++++
 mysql-test/include/stop_extra_server.inc     |  98 +++++
 mysql-test/lib/EXTRA_SERVER_README.md        | 136 +++++++
 mysql-test/lib/start_extra_server.pl         | 154 ++++++++
 mysql-test/main/extra_server_example.result  |  34 ++
 mysql-test/main/extra_server_example.test    |  22 ++
 mysql-test/main/replay_server_test.test      |  48 +++
 mysql-test/mariadb-test-run.pl               | 103 ++++++
 11 files changed, 1156 insertions(+), 1 deletion(-)
 create mode 100644 mysql-test/EXTRA_SERVER_QUICKSTART.txt
 create mode 100644 mysql-test/include/start_extra_server.inc
 create mode 100644 mysql-test/include/stop_extra_server.inc
 create mode 100644 mysql-test/lib/EXTRA_SERVER_README.md
 create mode 100755 mysql-test/lib/start_extra_server.pl
 create mode 100644 mysql-test/main/extra_server_example.result
 create mode 100644 mysql-test/main/extra_server_example.test
 create mode 100644 mysql-test/main/replay_server_test.test

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index b48caa0c2d694..d751863cb1e29 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -271,6 +271,11 @@ static const char *opt_plugin_dir;
 static const char *opt_suite_dir, *opt_overlay_dir;
 static size_t suite_dir_len, overlay_dir_len;
 
+/* ReplayTest mode variables */
+static MYSQL *replay_server_mysql= NULL;
+static const char *replay_server_socket= NULL;
+static my_bool replay_test_mode= FALSE;
+
 /* Precompiled re's */
 static regex_t ps_re;     /* the query can be run using PS protocol */
 static regex_t ps2_re;    /* the query can be run using PS protocol with second execution*/
@@ -1506,6 +1511,12 @@ void free_used_memory()
   uint i;
   DBUG_ENTER("free_used_memory");
 
+  if (replay_server_mysql)
+  {
+    mysql_close(replay_server_mysql);
+    replay_server_mysql= NULL;
+  }
+
   if (connections)
   {
     close_connections();
@@ -8318,6 +8329,273 @@ void run_execute_stmt(struct st_connection *cn, struct st_command *command, cons
 void run_close_stmt(struct st_connection *cn, struct st_command *command, const char *query,
                     size_t query_len, DYNAMIC_STRING *ds, DYNAMIC_STRING *ds_warnings);
 
+/*
+  ReplayTest mode helper functions
+*/
+
+/*
+  Ensure connection to replay server is established
+  Returns 0 on success, non-zero on error
+*/
+static int ensure_replay_server_connection()
+{
+  DBUG_ENTER("ensure_replay_server_connection");
+  
+  if (replay_server_mysql)
+    DBUG_RETURN(0);
+  
+  replay_server_mysql= mysql_init(NULL);
+  if (!replay_server_mysql)
+  {
+    fprintf(stdout, "ReplayTest: Failed to initialize MySQL handle for replay server\n");
+    DBUG_RETURN(1);
+  }
+  
+  if (!mysql_real_connect(replay_server_mysql, NULL, NULL, NULL, "test", 0,
+                          replay_server_socket, CLIENT_MULTI_STATEMENTS))
+  {
+    fprintf(stdout, "ReplayTest: Failed to connect to replay server at socket '%s': %d %s\n",
+            replay_server_socket, mysql_errno(replay_server_mysql),
+            mysql_error(replay_server_mysql));
+    mysql_close(replay_server_mysql);
+    replay_server_mysql= NULL;
+    DBUG_RETURN(1);
+  }
+  
+  verbose_msg("ReplayTest: Connected to replay server (database: test)");
+  DBUG_RETURN(0);
+}
+
+/*
+  Check if query starts with "EXPLAIN FORMAT=JSON"
+  Returns TRUE if it matches, FALSE otherwise
+*/
+static my_bool is_explain_format_json(const char *query, size_t query_len)
+{
+  const char *p= query;
+  const char *end= query + query_len;
+  
+  while (p < end && my_isspace(charset_info, *p))
+    p++;
+  
+  if (end - p < 7 || strncasecmp(p, "EXPLAIN", 7) != 0)
+    return FALSE;
+  p += 7;
+  
+  if (p >= end || !my_isspace(charset_info, *p))
+    return FALSE;
+  
+  while (p < end && my_isspace(charset_info, *p))
+    p++;
+  
+  if (end - p < 6 || strncasecmp(p, "FORMAT", 6) != 0)
+    return FALSE;
+  p += 6;
+  
+  while (p < end && my_isspace(charset_info, *p))
+    p++;
+  
+  if (p >= end || *p != '=')
+    return FALSE;
+  p++;
+  
+  while (p < end && my_isspace(charset_info, *p))
+    p++;
+  
+  if (end - p < 4 || strncasecmp(p, "JSON", 4) != 0)
+    return FALSE;
+  
+  return TRUE;
+}
+
+/*
+  Execute queries from SQL script on replay server
+  Split by ";\n" and execute each query
+  Append output from last query to ds
+*/
+static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
+{
+  DYNAMIC_STRING last_result;
+  const char *p= sql_script;
+  const char *query_start= p;
+  const char *last_query_start= NULL;
+  size_t last_query_len= 0;
+  DBUG_ENTER("execute_replay_queries");
+  
+  verbose_msg("ReplayTest: SQL script from optimizer_context:\n%s", sql_script);
+  
+  init_dynamic_string(&last_result, "", 1024, 1024);
+  
+  while (*p)
+  {
+    if (p[0] == ';' && p[1] == '\n')
+    {
+      size_t query_len= p - query_start;
+      const char *q= query_start;
+      const char *q_end= query_start + query_len;
+      
+      while (q < q_end && my_isspace(charset_info, *q))
+        q++;
+      
+      if (q < q_end)
+      {
+        last_query_start= query_start;
+        last_query_len= query_len;
+      }
+      
+      p += 2;
+      query_start= p;
+    }
+    else
+    {
+      p++;
+    }
+  }
+  
+  if (query_start < p)
+  {
+    const char *q= query_start;
+    const char *q_end= p;
+    while (q < q_end && my_isspace(charset_info, *q))
+      q++;
+    if (q < q_end)
+    {
+      last_query_start= query_start;
+      last_query_len= p - query_start;
+    }
+  }
+  
+  p= sql_script;
+  query_start= p;
+  
+  while (*p)
+  {
+    if (p[0] == ';' && p[1] == '\n')
+    {
+      size_t query_len= p - query_start;
+      const char *q= query_start;
+      const char *q_end= query_start + query_len;
+      
+      while (q < q_end && my_isspace(charset_info, *q))
+        q++;
+      
+      if (q < q_end)
+      {
+        my_bool is_last= (query_start == last_query_start && 
+                          query_len == last_query_len);
+        
+        verbose_msg("ReplayTest: Executing query on replay server (%s): %.*s",
+                    is_last ? "LAST" : "intermediate", (int)query_len, query_start);
+        
+        if (mysql_real_query(replay_server_mysql, query_start, query_len))
+        {
+          fprintf(stdout, "ReplayTest: Query failed on replay server: %d %s\n",
+                  mysql_errno(replay_server_mysql),
+                  mysql_error(replay_server_mysql));
+          fprintf(stdout, "ReplayTest: Failed query was: %.*s\n", (int)query_len, query_start);
+          dynstr_free(&last_result);
+          DBUG_VOID_RETURN;
+        }
+        
+        do
+        {
+          MYSQL_RES *res= mysql_store_result(replay_server_mysql);
+          if (res)
+          {
+            if (is_last)
+            {
+              MYSQL_FIELD *fields= mysql_fetch_fields(res);
+              uint num_fields= mysql_num_fields(res);
+              MYSQL_ROW row;
+              
+              if (!display_result_vertically)
+              {
+                append_table_headings(&last_result, fields, num_fields);
+              }
+              
+              while ((row= mysql_fetch_row(res)))
+              {
+                uint i;
+                ulong *lengths= mysql_fetch_lengths(res);
+                for (i= 0; i < num_fields; i++)
+                  append_field(&last_result, i, &fields[i],
+                              row[i], lengths[i], !row[i]);
+                if (!display_result_vertically)
+                  dynstr_append_mem(&last_result, "\n", 1);
+              }
+            }
+            mysql_free_result(res);
+          }
+        } while (mysql_next_result(replay_server_mysql) == 0);
+      }
+      
+      p += 2;
+      query_start= p;
+    }
+    else
+    {
+      p++;
+    }
+  }
+  
+  if (query_start < p)
+  {
+    const char *q= query_start;
+    const char *q_end= p;
+    while (q < q_end && my_isspace(charset_info, *q))
+      q++;
+    if (q < q_end)
+    {
+      size_t query_len= p - query_start;
+      
+      verbose_msg("ReplayTest: Executing final query on replay server: %.*s",
+                  (int)query_len, query_start);
+      
+      if (mysql_real_query(replay_server_mysql, query_start, query_len))
+      {
+        fprintf(stdout, "ReplayTest: Query failed on replay server: %d %s\n",
+                mysql_errno(replay_server_mysql),
+                mysql_error(replay_server_mysql));
+        fprintf(stdout, "ReplayTest: Failed query was: %.*s\n", (int)query_len, query_start);
+        dynstr_free(&last_result);
+        DBUG_VOID_RETURN;
+      }
+      
+      do
+      {
+        MYSQL_RES *res= mysql_store_result(replay_server_mysql);
+        if (res)
+        {
+          MYSQL_FIELD *fields= mysql_fetch_fields(res);
+          uint num_fields= mysql_num_fields(res);
+          MYSQL_ROW row;
+          
+          if (!display_result_vertically)
+          {
+            append_table_headings(&last_result, fields, num_fields);
+          }
+          
+          while ((row= mysql_fetch_row(res)))
+          {
+            uint i;
+            ulong *lengths= mysql_fetch_lengths(res);
+            for (i= 0; i < num_fields; i++)
+              append_field(&last_result, i, &fields[i],
+                          row[i], lengths[i], !row[i]);
+            if (!display_result_vertically)
+              dynstr_append_mem(&last_result, "\n", 1);
+          }
+          mysql_free_result(res);
+        }
+      } while (mysql_next_result(replay_server_mysql) == 0);
+    }
+  }
+  
+  dynstr_append_mem(ds, last_result.str, last_result.length);
+  dynstr_free(&last_result);
+  DBUG_VOID_RETURN;
+}
+
 /*
   Run query using MySQL C API
 
@@ -8338,6 +8616,7 @@ void run_query_normal(struct st_connection *cn, struct st_command *command,
   MYSQL_RES *res= 0;
   MYSQL *mysql= cn->mysql;
   int err= 0, counter= 0;
+  my_bool replay_mode_active= FALSE;
   DBUG_ENTER("run_query_normal");
   DBUG_PRINT("enter",("flags: %d", flags));
   DBUG_PRINT("enter", ("query: '%-.60s'", query));
@@ -8374,6 +8653,28 @@ void run_query_normal(struct st_connection *cn, struct st_command *command,
     break;
   }
 
+  /* ReplayTest mode: Set optimizer_record_context BEFORE sending EXPLAIN query */
+  if (replay_test_mode && (flags & QUERY_SEND_FLAG) && (flags & QUERY_REAP_FLAG) &&
+      is_explain_format_json(query, query_len))
+  {
+    replay_mode_active= TRUE;
+    verbose_msg("ReplayTest: Detected EXPLAIN FORMAT=JSON query, activating replay mode");
+    
+    /* Step 1: Set optimizer_record_context=1 */
+    if (mysql_real_query(mysql, "SET optimizer_record_context=1", 30))
+    {
+      fprintf(stdout, "ReplayTest: Failed to set optimizer_record_context: %d %s\n",
+              mysql_errno(mysql), mysql_error(mysql));
+      replay_mode_active= FALSE;
+    }
+    else
+    {
+      MYSQL_RES *tmp_res= mysql_store_result(mysql);
+      if (tmp_res)
+        mysql_free_result(tmp_res);
+    }
+  }
+
   if (flags & QUERY_SEND_FLAG)
   {
     /*
@@ -8431,7 +8732,61 @@ void run_query_normal(struct st_connection *cn, struct st_command *command,
 	if (!display_result_vertically)
 	  append_table_headings(ds, fields, num_fields);
 
-	append_result(ds, res);
+	/* ReplayTest mode: Replace EXPLAIN result with replay server output */
+	if (replay_mode_active && counter == 0)
+	{
+	  /* Free the EXPLAIN result - we won't use it */
+	  mysql_free_result(res);
+	  res= 0;
+	  
+	  /* Step 2: Query optimizer_context */
+	  fprintf(stdout, "ReplayTest: Loading context \n");
+	  if (mysql_real_query(mysql, 
+	      "SELECT context FROM information_schema.optimizer_context", 56))
+	  {
+	    fprintf(stdout, "ReplayTest: Failed to query optimizer_context: %d %s\n",
+	            mysql_errno(mysql), mysql_error(mysql));
+	  }
+	  else
+	  {
+	    MYSQL_RES *context_res= mysql_store_result(mysql);
+	    if (context_res && mysql_num_rows(context_res) > 0)
+	    {
+	      MYSQL_ROW context_row= mysql_fetch_row(context_res);
+	      if (context_row && context_row[0])
+	      {
+	        const char *sql_script= context_row[0];
+	        
+	        /* Step 3: Connect to replay server and execute queries */
+	        if (ensure_replay_server_connection() == 0)
+	        {
+	          execute_replay_queries(sql_script, ds);
+	        }
+	        else
+	        {
+	          fprintf(stdout, "ReplayTest: Failed to connect to replay server\n");
+	        }
+	      }
+	      else
+	      {
+	        fprintf(stdout, "ReplayTest: optimizer_context returned NULL\n");
+	      }
+	      mysql_free_result(context_res);
+	    }
+	    else
+	    {
+	      fprintf(stdout, "ReplayTest: optimizer_context returned no rows\n");
+	      if (context_res)
+	        mysql_free_result(context_res);
+	    }
+	  }
+	  
+	  replay_mode_active= FALSE;
+	}
+	else
+	{
+	  append_result(ds, res);
+	}
       }
 
       /*
@@ -10302,6 +10657,15 @@ int main(int argc, char **argv)
   var_set_string("MYSQLTEST_FILE", cur_file->file_name);
   init_re();
 
+  /* Check for ReplayTest mode */
+  replay_server_socket= getenv("REPLAY_SERVER_SOCKET");
+  if (replay_server_socket && replay_server_socket[0])
+  {
+    replay_test_mode= TRUE;
+    verbose_msg("ReplayTest mode enabled, replay server socket: %s", 
+                replay_server_socket);
+  }
+
   /* Cursor protocol implies ps protocol */
   if (cursor_protocol)
     ps_protocol= 1;
diff --git a/mariadb-plugin-columnstore.install.generated b/mariadb-plugin-columnstore.install.generated
index d987525f2a671..2b1434e58b9a1 100644
--- a/mariadb-plugin-columnstore.install.generated
+++ b/mariadb-plugin-columnstore.install.generated
@@ -1 +1,3 @@
 #File is generated by ColumnstoreLibrary.cmake, do not edit
+etc/mysql/columnstore.cnf # added in dbcon/mysql/CMakeLists.txt
+usr/local/mysql/lib/plugin/ha_columnstore.so # added in dbcon/mysql/CMakeLists.txt
diff --git a/mysql-test/EXTRA_SERVER_QUICKSTART.txt b/mysql-test/EXTRA_SERVER_QUICKSTART.txt
new file mode 100644
index 0000000000000..8e1000438d1e0
--- /dev/null
+++ b/mysql-test/EXTRA_SERVER_QUICKSTART.txt
@@ -0,0 +1,89 @@
+================================================================================
+EXTRA SERVER QUICK START GUIDE
+================================================================================
+
+This feature allows you to start additional MariaDB server instances during
+test execution while mysql-test-run is already running.
+
+BASIC USAGE
+-----------
+
+1. In your test file (.test):
+
+   # Start extra server
+   --let $extra_server_num= 1
+   --source include/start_extra_server.inc
+   
+   # Connect to it
+   --connect (extra1, 127.0.0.1, root, , test, $EXTRA_SERVER_PORT)
+   CREATE TABLE t1 (id INT);
+   SELECT * FROM t1;
+   
+   # Stop it
+   --disconnect extra1
+   --let $extra_server_num= 1
+   --source include/stop_extra_server.inc
+
+2. Run the test:
+
+   cd mysql-test
+   ./mysql-test-run main.extra_server_example
+
+WHAT IT DOES
+------------
+
+✓ Creates new data directory: var/extra_server_N/data (copied from install.db)
+✓ Picks non-conflicting port: MASTER_MYPORT + 10 + N
+✓ Creates unique socket: var/tmp/extra_server_N.sock
+✓ Starts mysqld with --skip-grant-tables (no password needed)
+✓ Exports connection info: $EXTRA_SERVER_PORT, $EXTRA_SERVER_SOCKET, etc.
+
+AVAILABLE VARIABLES AFTER START
+--------------------------------
+
+$EXTRA_SERVER_PORT    - Port number (e.g., 10011 for server 1)
+$EXTRA_SERVER_SOCKET  - Socket path
+$EXTRA_SERVER_DATADIR - Data directory path
+$EXTRA_SERVER_PID     - Process ID
+
+CUSTOM PORT/SOCKET
+------------------
+
+--let $extra_server_num= 2
+--let $extra_server_port= 15000
+--let $extra_server_socket= /tmp/my_custom.sock
+--source include/start_extra_server.inc
+
+MULTIPLE SERVERS
+----------------
+
+--let $extra_server_num= 1
+--source include/start_extra_server.inc
+
+--let $extra_server_num= 2
+--source include/start_extra_server.inc
+
+# Now you have two extra servers running!
+
+FILES CREATED
+-------------
+
+lib/start_extra_server.pl         - Perl script (main implementation)
+include/start_extra_server.inc    - Test include to start server
+include/stop_extra_server.inc     - Test include to stop server
+main/extra_server_example.test    - Example test
+lib/EXTRA_SERVER_README.md        - Full documentation
+
+TROUBLESHOOTING
+---------------
+
+If server fails to start, check:
+  var/log/extra_server_N.err
+
+Connection info is stored in:
+  var/tmp/extra_server_N.info
+
+Direct invocation (from Perl or shell):
+  perl lib/start_extra_server.pl <server_num> [port] [socket]
+
+================================================================================
diff --git a/mysql-test/include/start_extra_server.inc b/mysql-test/include/start_extra_server.inc
new file mode 100644
index 0000000000000..e768056501a10
--- /dev/null
+++ b/mysql-test/include/start_extra_server.inc
@@ -0,0 +1,105 @@
+# ==== Purpose ====
+#
+# Start an additional mysqld server instance while mysql-test-run is running.
+# This creates a new data directory (copied from var/install.db), picks a
+# non-conflicting port and socket, and starts the server.
+#
+# ==== Usage ====
+#
+# --let $extra_server_num= 1
+# [--let $extra_server_port= 13307]
+# [--let $extra_server_socket= /path/to/socket]
+# --source include/start_extra_server.inc
+#
+# After sourcing this file, the following variables will be set:
+#   $EXTRA_SERVER_PORT    - Port number of the extra server
+#   $EXTRA_SERVER_SOCKET  - Socket path of the extra server
+#   $EXTRA_SERVER_DATADIR - Data directory of the extra server
+#   $EXTRA_SERVER_PID     - Process ID of the extra server
+#
+# You can then connect to the server using:
+#   --connect (conn_name, 127.0.0.1, root, , test, $EXTRA_SERVER_PORT)
+#
+# ==== Parameters ====
+#
+# $extra_server_num
+#   Required. A unique number identifying this extra server instance.
+#   Must be unique across all extra servers started in the same test.
+#
+# $extra_server_port
+#   Optional. Custom port number for the server. If not specified,
+#   the port will be auto-calculated as MASTER_MYPORT + 10 + server_num.
+#
+# $extra_server_socket
+#   Optional. Custom socket path. If not specified, will use
+#   $MYSQLTEST_VARDIR/tmp/extra_server_N.sock
+#
+
+if (!$extra_server_num)
+{
+  --die extra_server_num must be set before sourcing start_extra_server.inc
+}
+
+--let $include_filename= start_extra_server.inc [server $extra_server_num]
+--source include/begin_include_file.inc
+
+# Export mysqltest variables to environment for Perl
+--let extra_server_num_env= $extra_server_num
+--let extra_server_port_env= $extra_server_port
+--let extra_server_socket_env= $extra_server_socket
+
+--perl
+  use strict;
+  use warnings;
+  
+  my $server_num = $ENV{extra_server_num_env} or die "extra_server_num not set";
+  my $port = $ENV{extra_server_port_env} || "";
+  my $socket = $ENV{extra_server_socket_env} || "";
+  
+  my $script = "$ENV{MYSQL_TEST_DIR}/lib/start_extra_server.pl";
+  die "Script not found: $script\n" unless -f $script;
+  
+  my $cmd = "perl $script $server_num";
+  $cmd .= " $port" if $port;
+  $cmd .= " $socket" if $socket;
+  
+  print "Executing: $cmd\n";
+  my $result = system($cmd);
+  if ($result != 0) {
+    die "Failed to start extra server $server_num (exit code: $result)\n";
+  }
+EOF
+
+# Read connection info from the info file
+--let $extra_server_info_file= $MYSQLTEST_VARDIR/tmp/extra_server_$extra_server_num.info
+
+--perl
+  use strict;
+  use warnings;
+  
+  my $file = $ENV{extra_server_info_file};
+  die "Info file not found: $file\n" unless -f $file;
+  
+  open my $fh, '<', $file or die "Cannot read $file: $!";
+  my %info;
+  while (<$fh>) {
+    chomp;
+    if (/^(\w+)=(.+)/) {
+      $info{$1} = $2;
+    }
+  }
+  close $fh;
+  
+  # Export to environment for mysqltest
+  $ENV{EXTRA_SERVER_PORT} = $info{PORT} if $info{PORT};
+  $ENV{EXTRA_SERVER_SOCKET} = $info{SOCKET} if $info{SOCKET};
+  $ENV{EXTRA_SERVER_DATADIR} = $info{DATADIR} if $info{DATADIR};
+  $ENV{EXTRA_SERVER_PID} = $info{PID} if $info{PID};
+  
+  print "Extra server $ENV{extra_server_num_env} connection info:\n";
+  print "  PORT=$info{PORT}\n" if $info{PORT};
+  print "  SOCKET=$info{SOCKET}\n" if $info{SOCKET};
+EOF
+
+--let $include_filename= start_extra_server.inc [server $extra_server_num]
+--source include/end_include_file.inc
diff --git a/mysql-test/include/stop_extra_server.inc b/mysql-test/include/stop_extra_server.inc
new file mode 100644
index 0000000000000..474686073b70f
--- /dev/null
+++ b/mysql-test/include/stop_extra_server.inc
@@ -0,0 +1,98 @@
+# ==== Purpose ====
+#
+# Stop an extra server instance that was started with start_extra_server.inc
+#
+# ==== Usage ====
+#
+# --let $extra_server_num= 1
+# --source include/stop_extra_server.inc
+#
+# ==== Parameters ====
+#
+# $extra_server_num
+#   Required. The number of the extra server to stop (same number used
+#   when starting it with start_extra_server.inc).
+#
+
+if (!$extra_server_num)
+{
+  --die extra_server_num must be set before sourcing stop_extra_server.inc
+}
+
+--let $include_filename= stop_extra_server.inc [server $extra_server_num]
+--source include/begin_include_file.inc
+
+# Export mysqltest variable to environment for Perl
+--let extra_server_num_env= $extra_server_num
+
+--perl
+  use strict;
+  use warnings;
+  use POSIX ":sys_wait_h";
+  
+  my $server_num = $ENV{extra_server_num_env} or die "extra_server_num not set";
+  my $vardir = $ENV{MYSQLTEST_VARDIR} or die "MYSQLTEST_VARDIR not set";
+  my $info_file = "$vardir/tmp/extra_server_$server_num.info";
+  
+  unless (-f $info_file) {
+    print "Warning: Info file not found: $info_file\n";
+    print "Server may not be running or already stopped.\n";
+    exit 0;
+  }
+  
+  # Read PID and other info
+  open my $fh, '<', $info_file or die "Cannot read $info_file: $!";
+  my ($pid, $pid_file, $socket);
+  while (<$fh>) {
+    chomp;
+    $pid = $1 if /^PID=(.+)/;
+    $pid_file = $1 if /^PID_FILE=(.+)/;
+    $socket = $1 if /^SOCKET=(.+)/;
+  }
+  close $fh;
+  
+  unless ($pid) {
+    print "Warning: No PID found in $info_file\n";
+    unlink $info_file;
+    exit 0;
+  }
+  
+  print "Stopping extra server $server_num (PID: $pid)...\n";
+  
+  # Send SIGTERM to server
+  if (kill 0, $pid) {
+    kill 'TERM', $pid;
+    
+    # Wait for process to exit (up to 10 seconds)
+    my $max_wait = 10;
+    my $waited = 0;
+    while ($waited < $max_wait) {
+      my $result = waitpid($pid, WNOHANG);
+      if ($result == $pid || $result == -1) {
+        print "Server process $pid has exited\n";
+        last;
+      }
+      sleep 1;
+      $waited++;
+    }
+    
+    # If still running, send SIGKILL
+    if ($waited >= $max_wait && kill 0, $pid) {
+      print "Server did not stop gracefully, sending SIGKILL...\n";
+      kill 'KILL', $pid;
+      sleep 1;
+    }
+  } else {
+    print "Process $pid is not running\n";
+  }
+  
+  # Cleanup files
+  unlink $info_file if -f $info_file;
+  unlink $pid_file if $pid_file && -f $pid_file;
+  unlink $socket if $socket && -S $socket;
+  
+  print "Extra server $server_num stopped\n";
+EOF
+
+--let $include_filename= stop_extra_server.inc [server $extra_server_num]
+--source include/end_include_file.inc
diff --git a/mysql-test/lib/EXTRA_SERVER_README.md b/mysql-test/lib/EXTRA_SERVER_README.md
new file mode 100644
index 0000000000000..d40508c965329
--- /dev/null
+++ b/mysql-test/lib/EXTRA_SERVER_README.md
@@ -0,0 +1,136 @@
+# Extra Server Script for MySQL Test Framework
+
+## Overview
+
+This script allows you to dynamically start additional MariaDB server instances during test execution while `mysql-test-run` is already running. This is useful for testing scenarios that require multiple independent server instances.
+
+## Features
+
+- **Dynamic server creation**: Start servers on-demand during test execution
+- **Automatic port allocation**: Non-conflicting ports (base_port + 10 + N)
+- **Automatic socket allocation**: Unique socket paths per server
+- **Data directory management**: Copies from existing `var/install.db`
+- **Connection info export**: Provides host, port, socket, datadir, PID
+
+## Files
+
+- `lib/start_extra_server.pl` - Perl script that starts the extra server
+- `include/start_extra_server.inc` - Test include file to start server
+- `include/stop_extra_server.inc` - Test include file to stop server
+- `main/extra_server_example.test` - Example test demonstrating usage
+
+## Usage
+
+### Starting an Extra Server
+
+```sql
+# Set the server number (must be unique)
+--let $extra_server_num= 1
+
+# Optional: specify custom port
+# --let $extra_server_port= 13307
+
+# Optional: specify custom socket
+# --let $extra_server_socket= /path/to/socket
+
+# Start the server
+--source include/start_extra_server.inc
+```
+
+After starting, the following variables are available:
+- `$EXTRA_SERVER_PORT` - Port number
+- `$EXTRA_SERVER_SOCKET` - Socket path
+- `$EXTRA_SERVER_DATADIR` - Data directory
+- `$EXTRA_SERVER_PID` - Process ID
+
+### Connecting to the Extra Server
+
+```sql
+--connect (conn_name, 127.0.0.1, root, , test, $EXTRA_SERVER_PORT)
+SELECT "Connected!" AS status;
+# ... perform operations ...
+--disconnect conn_name
+```
+
+### Stopping the Extra Server
+
+```sql
+--let $extra_server_num= 1
+--source include/stop_extra_server.inc
+```
+
+## Port Allocation
+
+Ports are automatically calculated to avoid conflicts:
+- Master servers: `base_port + 0`, `base_port + 1`
+- Slave servers: `base_port + 2`, `base_port + 3`, `base_port + 4`
+- Extra servers: `base_port + 10 + server_num`
+
+Default `base_port` is typically 10000 (or `MASTER_MYPORT` if set).
+
+## Data Directory
+
+The script copies `var/install.db` to `var/extra_server_N/data`, so:
+- No bootstrap needed (system tables already exist)
+- Fast startup
+- Clean slate for each server
+
+## Server Configuration
+
+The extra server is started with:
+- `--skip-grant-tables` (for easy test access)
+- `--default-storage-engine=myisam`
+- `--loose-skip-innodb` (for faster startup)
+- Minimal memory settings
+
+## Example Test
+
+See `main/extra_server_example.test` for a complete working example.
+
+## Invocation from mysqltest.cc
+
+The script can be invoked using the `--exec` command in test files:
+
+```sql
+--exec perl $MYSQL_TEST_DIR/lib/start_extra_server.pl 1
+```
+
+Or more conveniently via the include files as shown above.
+
+## Troubleshooting
+
+### Server fails to start
+
+Check the log file: `var/log/extra_server_N.err`
+
+### Port conflicts
+
+Specify a custom port:
+```sql
+--let $extra_server_port= 15000
+```
+
+### Connection issues
+
+Verify the server is running:
+```sql
+--exec ps aux | grep extra_server
+```
+
+Check the info file:
+```sql
+--exec cat $MYSQLTEST_VARDIR/tmp/extra_server_1.info
+```
+
+## Limitations
+
+- Servers run with `--skip-grant-tables` (no authentication)
+- InnoDB is disabled by default (use `--loose-innodb` if needed)
+- No automatic cleanup on test failure (use `--force` in mysql-test-run)
+
+## Future Enhancements
+
+- Support for custom mysqld options
+- Better error handling and diagnostics
+- Automatic cleanup on test failure
+- Support for replication setup between extra servers
diff --git a/mysql-test/lib/start_extra_server.pl b/mysql-test/lib/start_extra_server.pl
new file mode 100755
index 0000000000000..07dfc556575e9
--- /dev/null
+++ b/mysql-test/lib/start_extra_server.pl
@@ -0,0 +1,154 @@
+#!/usr/bin/env perl
+# Copyright (c) 2026, MariaDB Corporation.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1335  USA
+
+use strict;
+use warnings;
+use File::Path qw(make_path remove_tree);
+use File::Basename;
+use File::Copy;
+use POSIX ":sys_wait_h";
+
+# Parse arguments
+my $vardir = $ENV{MYSQLTEST_VARDIR} or die "MYSQLTEST_VARDIR not set\n";
+my $server_num = shift @ARGV or die "Usage: $0 <server_num> [port] [socket]\n";
+my $custom_port = shift @ARGV;
+my $custom_socket = shift @ARGV;
+
+# Calculate port (base + 10 + server_num if not custom)
+my $base_port = $ENV{MASTER_MYPORT} || 10000;
+my $port = $custom_port || ($base_port + 10 + $server_num);
+my $socket = $custom_socket || "$vardir/tmp/extra_server_$server_num.sock";
+
+# Create data directory
+my $datadir = "$vardir/extra_server_$server_num/data";
+my $install_db = "$vardir/install.db";
+
+die "install.db not found at $install_db\n" unless -d $install_db;
+
+# Create parent directory if needed
+my $server_dir = "$vardir/extra_server_$server_num";
+make_path($server_dir) unless -d $server_dir;
+
+# Copy install.db to new datadir
+if (-d $datadir) {
+    print "Removing existing datadir: $datadir\n";
+    remove_tree($datadir);
+}
+
+print "Copying $install_db to $datadir...\n";
+# Use cp -a to preserve permissions and attributes
+system("cp", "-a", $install_db, $datadir) == 0
+    or die "Failed to copy $install_db to $datadir: $!\n";
+
+# Ensure proper permissions on the datadir
+system("chmod", "-R", "u+rwX", $datadir) == 0
+    or warn "Warning: Failed to set permissions on $datadir\n";
+
+# Start mysqld
+my $mysqld = $ENV{MYSQLD} or die "MYSQLD environment variable not set\n";
+die "mysqld binary not found at $mysqld\n" unless -x $mysqld;
+
+my $pid_file = "$server_dir/mysqld.pid";
+my $log_file = "$vardir/log/extra_server_$server_num.err";
+my $general_log_file = "$vardir/log/extra_server_$server_num.log";
+
+# Ensure log directory exists
+make_path("$vardir/log") unless -d "$vardir/log";
+
+my @mysqld_args = (
+    $mysqld,
+    "--no-defaults",
+    "--datadir=$datadir",
+    "--port=$port",
+    "--socket=$socket",
+    "--pid-file=$pid_file",
+    "--log-error=$log_file",
+    "--general-log=1",
+    "--general-log-file=$general_log_file",
+    "--skip-networking=0",
+    "--skip-grant-tables",
+    "--key-buffer-size=1M",
+    "--sort-buffer-size=256K",
+    "--max-heap-table-size=1M",
+);
+
+print "Starting mysqld on port $port with socket $socket...\n";
+print "Command: " . join(" ", @mysqld_args) . "\n";
+
+# Fork and start server
+my $pid = fork();
+die "Fork failed: $!\n" unless defined $pid;
+
+if ($pid == 0) {
+    # Child process - start server
+    # Redirect stdout/stderr to log file
+    open STDOUT, '>>', $log_file or die "Cannot redirect STDOUT: $!\n";
+    open STDERR, '>>', $log_file or die "Cannot redirect STDERR: $!\n";
+    exec(@mysqld_args) or die "Failed to exec mysqld: $!\n";
+}
+
+# Parent - wait for server to be ready
+print "Server process started with PID $pid\n";
+print "Waiting for server to be ready...\n";
+
+# Wait for socket file to appear (up to 30 seconds)
+my $max_wait = 30;
+my $waited = 0;
+while ($waited < $max_wait) {
+    if (-S $socket) {
+        print "Socket file created: $socket\n";
+        last;
+    }
+    sleep 1;
+    $waited++;
+    
+    # Check if process is still alive
+    my $result = waitpid($pid, WNOHANG);
+    if ($result == $pid) {
+        die "Server process died during startup. Check $log_file for errors.\n";
+    }
+}
+
+if ($waited >= $max_wait) {
+    kill 'TERM', $pid;
+    die "Timeout waiting for server to start. Check $log_file for errors.\n";
+}
+
+# Additional wait for server to be fully ready
+sleep 2;
+
+# Write connection info to file
+my $info_file = "$vardir/tmp/extra_server_$server_num.info";
+open my $fh, '>', $info_file or die "Cannot write $info_file: $!\n";
+print $fh "HOST=127.0.0.1\n";
+print $fh "PORT=$port\n";
+print $fh "SOCKET=$socket\n";
+print $fh "DATADIR=$datadir\n";
+print $fh "PID=$pid\n";
+print $fh "PID_FILE=$pid_file\n";
+print $fh "LOG_FILE=$log_file\n";
+print $fh "GENERAL_LOG_FILE=$general_log_file\n";
+close $fh;
+
+print "Extra server $server_num started successfully\n";
+print "Connection info written to $info_file\n";
+print "  Host: 127.0.0.1\n";
+print "  Port: $port\n";
+print "  Socket: $socket\n";
+print "  Datadir: $datadir\n";
+print "  General log: $general_log_file\n";
+
+exit 0;
diff --git a/mysql-test/main/extra_server_example.result b/mysql-test/main/extra_server_example.result
new file mode 100644
index 0000000000000..0c6c39cb46a9e
--- /dev/null
+++ b/mysql-test/main/extra_server_example.result
@@ -0,0 +1,34 @@
+include/start_extra_server.inc [server 1]
+Executing: perl MYSQL_TEST_DIR/lib/start_extra_server.pl 1
+Copying MYSQLTEST_VARDIR/install.db to MYSQLTEST_VARDIR/extra_server_1/data...
+Starting mysqld on port PORT with socket SOCKET...
+Command: MYSQLD --no-defaults --datadir=MYSQLTEST_VARDIR/extra_server_1/data --port=PORT --socket=SOCKET --pid-file=MYSQLTEST_VARDIR/extra_server_1/mysqld.pid --log-error=MYSQLTEST_VARDIR/log/extra_server_1.err --skip-networking=0 --skip-grant-tables --default-storage-engine=myisam --loose-skip-innodb --key-buffer-size=1M --sort-buffer-size=256K --max-heap-table-size=1M
+Server process started with PID PID
+Waiting for server to be ready...
+Socket file created: SOCKET
+Extra server 1 started successfully
+Connection info written to MYSQLTEST_VARDIR/tmp/extra_server_1.info
+  Host: 127.0.0.1
+  Port: PORT
+  Socket: SOCKET
+  Datadir: MYSQLTEST_VARDIR/extra_server_1/data
+Extra server 1 connection info:
+  PORT=PORT
+  SOCKET=SOCKET
+include/start_extra_server.inc [server 1]
+status
+Connected to extra server
+CREATE TABLE t1 (id INT);
+INSERT INTO t1 VALUES (1), (2), (3);
+SELECT * FROM t1;
+id
+1
+2
+3
+status
+On default server
+include/stop_extra_server.inc [server 1]
+Stopping extra server 1 (PID: PID)...
+Server process PID has exited
+Extra server 1 stopped
+include/stop_extra_server.inc [server 1]
diff --git a/mysql-test/main/extra_server_example.test b/mysql-test/main/extra_server_example.test
new file mode 100644
index 0000000000000..e11be32432872
--- /dev/null
+++ b/mysql-test/main/extra_server_example.test
@@ -0,0 +1,22 @@
+# Test starting an extra server instance
+--source include/not_embedded.inc
+
+# Start extra server
+--let $extra_server_num= 1
+--source include/start_extra_server.inc
+
+# Connect to it
+--connect (extra1, 127.0.0.1, root, , test, $EXTRA_SERVER_PORT)
+SELECT "Connected to extra server" AS status;
+CREATE TABLE t1 (id INT);
+INSERT INTO t1 VALUES (1), (2), (3);
+SELECT * FROM t1;
+
+# Back to default
+--connection default
+SELECT "On default server" AS status;
+
+# Stop extra server
+--disconnect extra1
+--let $extra_server_num= 1
+--source include/stop_extra_server.inc
diff --git a/mysql-test/main/replay_server_test.test b/mysql-test/main/replay_server_test.test
new file mode 100644
index 0000000000000..a126bc545ed40
--- /dev/null
+++ b/mysql-test/main/replay_server_test.test
@@ -0,0 +1,48 @@
+# Test that replay server is started and REPLAY_SERVER_SOCKET is set
+--source include/not_embedded.inc
+
+--perl
+if ($ENV{REPLAY_SERVER_SOCKET}) {
+  print "REPLAY_SERVER_SOCKET is set: $ENV{REPLAY_SERVER_SOCKET}\n";
+} else {
+  print "REPLAY_SERVER_SOCKET is NOT set\n";
+}
+EOF
+
+# Try to connect to the replay server if socket is set
+--perl
+if ($ENV{REPLAY_SERVER_SOCKET}) {
+  my $socket = $ENV{REPLAY_SERVER_SOCKET};
+  print "Checking socket: $socket\n";
+  print "Socket exists: ", (-e $socket ? "YES" : "NO"), "\n";
+  print "Is socket: ", (-S $socket ? "YES" : "NO"), "\n";
+  
+  # Check if PID is set and process is running
+  if ($ENV{REPLAY_SERVER_PID}) {
+    my $pid = $ENV{REPLAY_SERVER_PID};
+    print "Replay server PID: $pid\n";
+    my $running = kill 0, $pid;
+    print "Process running: ", ($running ? "YES" : "NO"), "\n";
+  }
+  
+  # List files in the socket directory
+  my $socket_dir = $socket;
+  $socket_dir =~ s{/[^/]+$}{};
+  print "Socket directory: $socket_dir\n";
+  if (-d $socket_dir) {
+    opendir(my $dh, $socket_dir);
+    my @files = grep { !/^\./ } readdir($dh);
+    closedir($dh);
+    print "Files in socket dir: ", join(", ", @files), "\n";
+  }
+}
+EOF
+
+# Test ReplayTest mode with EXPLAIN FORMAT=JSON
+CREATE TABLE t1 (a INT, b INT, KEY(a));
+INSERT INTO t1 VALUES (1,1), (2,2), (3,3);
+
+# This should trigger ReplayTest mode if REPLAY_SERVER_SOCKET is set
+EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE a = 1;
+
+DROP TABLE t1;
diff --git a/mysql-test/mariadb-test-run.pl b/mysql-test/mariadb-test-run.pl
index c3816654d08fe..2ef660255c137 100755
--- a/mysql-test/mariadb-test-run.pl
+++ b/mysql-test/mariadb-test-run.pl
@@ -281,6 +281,8 @@ END
 our $opt_gprof;
 our %gprof_dirs;
 
+our $opt_replay_server;  # Start an extra server for replay
+
 my $config; # The currently running config
 my $current_config_name; # The currently running config file template
 
@@ -425,6 +427,12 @@ sub main {
   {
     mysql_install_db(default_mysqld(), "$opt_vardir/install.db");
     make_readonly("$opt_vardir/install.db");
+    
+    # Start replay server if --replay-server option is specified
+    if ( $opt_replay_server )
+    {
+      start_replay_server();
+    }
   }
   if ($opt_dry_run)
   {
@@ -596,6 +604,9 @@ sub main {
 
   remove_vardir_subs() if $opt_clean_vardir;
 
+  # Stop replay server if it was started
+  stop_replay_server() if $opt_replay_server;
+
   exit(0);
 }
 
@@ -1283,6 +1294,7 @@ sub command_line_setup {
              'skip-test-list=s'         => \@opt_skip_test_list,
              'xml-report=s'             => \$opt_xml_report,
              'open-files-limit=i',      => \$opt_open_files_limit,
+             'replay-server'            => \$opt_replay_server,
 
              My::Debugger::options(),
              My::CoreDump::options(),
@@ -3031,6 +3043,95 @@ sub initialize_servers {
 }
 
 
+sub start_replay_server {
+  mtr_report("Starting replay server...");
+  
+  my $replay_server_num = 1;
+  my $script = "$glob_mysql_test_dir/lib/start_extra_server.pl";
+  
+  unless (-f $script) {
+    mtr_error("Replay server script not found: $script");
+  }
+  
+  # Set required environment variables for the script
+  # (environment_setup() has already been called, so most are already set)
+  $ENV{MYSQLTEST_VARDIR} = $opt_vardir unless $ENV{MYSQLTEST_VARDIR};
+  $ENV{MASTER_MYPORT} = $baseport unless $ENV{MASTER_MYPORT};
+  $ENV{MYSQL_TEST_DIR} = $glob_mysql_test_dir unless $ENV{MYSQL_TEST_DIR};
+  # MYSQLD should already be set by environment_setup(), but set it if not
+  $ENV{MYSQLD} = find_mysqld($basedir) unless $ENV{MYSQLD};
+  
+  # Use a custom socket path in the replay server directory to avoid cleanup
+  my $replay_socket = "$opt_vardir/extra_server_$replay_server_num/mysqld.sock";
+  
+  # Call the start_extra_server.pl script with custom socket
+  my $cmd = "perl $script $replay_server_num '' $replay_socket";
+  my $result = system($cmd);
+  
+  if ($result != 0) {
+    mtr_error("Failed to start replay server (exit code: $result)");
+  }
+  
+  # Read connection info
+  my $info_file = "$opt_vardir/tmp/extra_server_$replay_server_num.info";
+  unless (-f $info_file) {
+    mtr_error("Replay server info file not found: $info_file");
+  }
+  
+  open my $fh, '<', $info_file or mtr_error("Cannot read $info_file: $!");
+  my %info;
+  while (<$fh>) {
+    chomp;
+    if (/^(\w+)=(.+)/) {
+      $info{$1} = $2;
+    }
+  }
+  close $fh;
+  
+  # Store for cleanup and export to environment
+  $ENV{REPLAY_SERVER_SOCKET} = $info{SOCKET};
+  $ENV{REPLAY_SERVER_PID} = $info{PID};
+  
+  mtr_report("Replay server started on socket: $info{SOCKET}");
+}
+
+
+sub stop_replay_server {
+  return unless $opt_replay_server;
+  return unless $ENV{REPLAY_SERVER_PID};
+  
+  mtr_report("Stopping replay server...");
+  
+  my $pid = $ENV{REPLAY_SERVER_PID};
+  
+  # Send SIGTERM
+  if (kill 0, $pid) {
+    kill 'TERM', $pid;
+    
+    # Wait for process to exit (up to 10 seconds)
+    my $max_wait = 10;
+    my $waited = 0;
+    while ($waited < $max_wait) {
+      my $result = waitpid($pid, WNOHANG);
+      last if ($result == $pid || $result == -1);
+      sleep 1;
+      $waited++;
+    }
+    
+    # Force kill if still running
+    if ($waited >= $max_wait && kill 0, $pid) {
+      kill 'KILL', $pid;
+    }
+  }
+  
+  # Cleanup info file
+  my $info_file = "$opt_vardir/tmp/extra_server_1.info";
+  unlink $info_file if -f $info_file;
+  
+  mtr_report("Replay server stopped");
+}
+
+
 #
 # Remove all newline characters expect after semicolon
 #
@@ -6026,6 +6127,8 @@ ($)
   timer                 Show test case execution time.
   verbose               More verbose output(use multiple times for even more)
   verbose-restart       Write when and why servers are restarted
+  replay-server         Start an extra server instance before running tests.
+                        Socket path available via REPLAY_SERVER_SOCKET env var.
   start                 Only initialize and start the servers, using the
                         startup settings for the first specified test case
                         Example:

From 8cbdbe727b7f160b8593b82e955cd5ed804e02fb Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Sun, 19 Apr 2026 19:35:52 +0300
Subject: [PATCH 02/50] MDEV-39368: Add --replay-server-manual.

---
 mysql-test/mariadb-test-run.pl | 163 ++++++++++++++++++++++++++++++++-
 1 file changed, 161 insertions(+), 2 deletions(-)

diff --git a/mysql-test/mariadb-test-run.pl b/mysql-test/mariadb-test-run.pl
index 2ef660255c137..de4e3347b44bf 100755
--- a/mysql-test/mariadb-test-run.pl
+++ b/mysql-test/mariadb-test-run.pl
@@ -282,6 +282,7 @@ END
 our %gprof_dirs;
 
 our $opt_replay_server;  # Start an extra server for replay
+our $opt_replay_server_manual;  # Print replay server command and wait for manual start
 
 my $config; # The currently running config
 my $current_config_name; # The currently running config file template
@@ -433,6 +434,10 @@ sub main {
     {
       start_replay_server();
     }
+    elsif ( $opt_replay_server_manual )
+    {
+      start_replay_server_manual();
+    }
   }
   if ($opt_dry_run)
   {
@@ -605,7 +610,7 @@ sub main {
   remove_vardir_subs() if $opt_clean_vardir;
 
   # Stop replay server if it was started
-  stop_replay_server() if $opt_replay_server;
+  stop_replay_server() if ($opt_replay_server || $opt_replay_server_manual);
 
   exit(0);
 }
@@ -1295,6 +1300,7 @@ sub command_line_setup {
              'xml-report=s'             => \$opt_xml_report,
              'open-files-limit=i',      => \$opt_open_files_limit,
              'replay-server'            => \$opt_replay_server,
+             'replay-server-manual'     => \$opt_replay_server_manual,
 
              My::Debugger::options(),
              My::CoreDump::options(),
@@ -3096,8 +3102,158 @@ sub start_replay_server {
 }
 
 
+sub start_replay_server_manual {
+  mtr_report("Starting replay server in manual mode...");
+  
+  my $replay_server_num = 1;
+  
+  # Set required environment variables
+  $ENV{MYSQLTEST_VARDIR} = $opt_vardir unless $ENV{MYSQLTEST_VARDIR};
+  $ENV{MASTER_MYPORT} = $baseport unless $ENV{MASTER_MYPORT};
+  $ENV{MYSQL_TEST_DIR} = $glob_mysql_test_dir unless $ENV{MYSQL_TEST_DIR};
+  $ENV{MYSQLD} = find_mysqld($basedir) unless $ENV{MYSQLD};
+  
+  my $mysqld = $ENV{MYSQLD};
+  die "mysqld binary not found at $mysqld\n" unless -x $mysqld;
+  
+  # Calculate paths
+  my $base_port = $ENV{MASTER_MYPORT} || 10000;
+  my $port = $base_port + 10 + $replay_server_num;
+  my $socket = "$opt_vardir/extra_server_$replay_server_num/mysqld.sock";
+  my $server_dir = "$opt_vardir/extra_server_$replay_server_num";
+  my $datadir = "$server_dir/data";
+  my $install_db = "$opt_vardir/install.db";
+  my $pid_file = "$server_dir/mysqld.pid";
+  my $log_file = "$opt_vardir/log/extra_server_$replay_server_num.err";
+  my $general_log_file = "$opt_vardir/log/extra_server_$replay_server_num.log";
+  
+  die "install.db not found at $install_db\n" unless -d $install_db;
+  
+  # Create server directory
+  use File::Path qw(make_path remove_tree);
+  make_path($server_dir) unless -d $server_dir;
+  make_path("$opt_vardir/log") unless -d "$opt_vardir/log";
+  
+  # Prepare datadir
+  if (-d $datadir) {
+    mtr_report("Removing existing datadir: $datadir");
+    remove_tree($datadir);
+  }
+  
+  mtr_report("Copying $install_db to $datadir...");
+  system("cp", "-a", $install_db, $datadir) == 0
+    or die "Failed to copy $install_db to $datadir: $!\n";
+  
+  # Ensure proper permissions
+  system("chmod", "-R", "u+rwX", $datadir) == 0
+    or warn "Warning: Failed to set permissions on $datadir\n";
+  
+  # Build command line
+  my @mysqld_args = (
+    $mysqld,
+    "--no-defaults",
+    "--datadir=$datadir",
+    "--port=$port",
+    "--socket=$socket",
+    "--pid-file=$pid_file",
+    "--log-error=$log_file",
+    "--general-log=1",
+    "--general-log-file=$general_log_file",
+    "--skip-networking=0",
+    "--skip-grant-tables",
+    "--key-buffer-size=1M",
+    "--sort-buffer-size=256K",
+    "--max-heap-table-size=1M",
+  );
+  
+  # Print command line for user
+  mtr_report("=" x 70);
+  mtr_report("REPLAY SERVER MANUAL MODE");
+  mtr_report("=" x 70);
+  mtr_report("");
+  mtr_report("Please start the replay server with the following command:");
+  mtr_report("");
+  mtr_report(join(" \\\n  ", @mysqld_args));
+  mtr_report("");
+  mtr_report("Or run under gdb:");
+  mtr_report("gdb --args " . join(" \\\n  ", @mysqld_args));
+  mtr_report("");
+  mtr_report("Waiting for socket file to appear: $socket");
+  mtr_report("(Timeout: 300 seconds)");
+  mtr_report("=" x 70);
+  
+  # Wait for socket file to appear
+  my $max_wait = 300;  # 5 minutes
+  my $waited = 0;
+  my $last_msg = 0;
+  
+  while ($waited < $max_wait) {
+    if (-S $socket) {
+      mtr_report("Socket file detected: $socket");
+      last;
+    }
+    
+    sleep 1;
+    $waited++;
+    
+    # Print progress every 10 seconds
+    if ($waited - $last_msg >= 10) {
+      mtr_report("Still waiting for socket... ($waited seconds elapsed)");
+      $last_msg = $waited;
+    }
+  }
+  
+  if ($waited >= $max_wait) {
+    die "Timeout waiting for replay server socket to appear: $socket\n";
+  }
+  
+  # Give server a moment to be fully ready
+  sleep 2;
+  
+  # Detect PID
+  my $pid;
+  
+  # Try to read from pid file
+  if (-f $pid_file) {
+    open my $fh, '<', $pid_file or warn "Cannot read $pid_file: $!\n";
+    if ($fh) {
+      $pid = <$fh>;
+      chomp $pid if defined $pid;
+      close $fh;
+    }
+  }
+  
+  # Fallback: use lsof to find process using the socket
+  if (!$pid || !kill(0, $pid)) {
+    my $lsof_output = `lsof -t $socket 2>/dev/null`;
+    chomp $lsof_output if $lsof_output;
+    $pid = $lsof_output if $lsof_output && $lsof_output =~ /^\d+$/;
+  }
+  
+  # Fallback: use fuser
+  if (!$pid || !kill(0, $pid)) {
+    my $fuser_output = `fuser $socket 2>/dev/null`;
+    if ($fuser_output && $fuser_output =~ /(\d+)/) {
+      $pid = $1;
+    }
+  }
+  
+  if (!$pid || !kill(0, $pid)) {
+    die "Could not detect PID of replay server. Please check if it's running.\n";
+  }
+  
+  # Store for cleanup and export to environment
+  $ENV{REPLAY_SERVER_SOCKET} = $socket;
+  $ENV{REPLAY_SERVER_PID} = $pid;
+  
+  mtr_report("Replay server detected with PID: $pid");
+  mtr_report("Socket: $socket");
+  mtr_report("Replay server is ready!");
+}
+
+
 sub stop_replay_server {
-  return unless $opt_replay_server;
+  return unless ($opt_replay_server || $opt_replay_server_manual);
   return unless $ENV{REPLAY_SERVER_PID};
   
   mtr_report("Stopping replay server...");
@@ -6129,6 +6285,9 @@ ($)
   verbose-restart       Write when and why servers are restarted
   replay-server         Start an extra server instance before running tests.
                         Socket path available via REPLAY_SERVER_SOCKET env var.
+  replay-server-manual  Print replay server command line and wait for user to
+                        start it manually. Useful for running under debugger.
+                        MTR will wait for socket and manage server lifecycle.
   start                 Only initialize and start the servers, using the
                         startup settings for the first specified test case
                         Example:

From d93bb2fe671ba31055353ba741e4a1818a125e09 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Mon, 20 Apr 2026 10:43:52 +0300
Subject: [PATCH 03/50] MDEV-39368: Make --replay-server[-manual] save the
 output of last EXPLAIN in the replay.

The last command is set "optimizer_replay_context=null"...
---
 client/mysqltest.cc                     | 106 ++++++++++--------------
 mysql-test/main/replay_server_test.test |   1 +
 2 files changed, 45 insertions(+), 62 deletions(-)

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index d751863cb1e29..a0d011d180624 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -8415,17 +8415,17 @@ static my_bool is_explain_format_json(const char *query, size_t query_len)
 */
 static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
 {
-  DYNAMIC_STRING last_result;
+  DYNAMIC_STRING result;
   const char *p= sql_script;
   const char *query_start= p;
-  const char *last_query_start= NULL;
-  size_t last_query_len= 0;
+  my_bool found_explain= FALSE;
   DBUG_ENTER("execute_replay_queries");
   
   verbose_msg("ReplayTest: SQL script from optimizer_context:\n%s", sql_script);
   
-  init_dynamic_string(&last_result, "", 1024, 1024);
+  init_dynamic_string(&result, "", 1024, 1024);
   
+  /* Single-pass execution: stop at first EXPLAIN FORMAT=JSON */
   while (*p)
   {
     if (p[0] == ';' && p[1] == '\n')
@@ -8434,75 +8434,38 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
       const char *q= query_start;
       const char *q_end= query_start + query_len;
       
+      /* Skip leading whitespace */
       while (q < q_end && my_isspace(charset_info, *q))
         q++;
       
       if (q < q_end)
       {
-        last_query_start= query_start;
-        last_query_len= query_len;
-      }
-      
-      p += 2;
-      query_start= p;
-    }
-    else
-    {
-      p++;
-    }
-  }
-  
-  if (query_start < p)
-  {
-    const char *q= query_start;
-    const char *q_end= p;
-    while (q < q_end && my_isspace(charset_info, *q))
-      q++;
-    if (q < q_end)
-    {
-      last_query_start= query_start;
-      last_query_len= p - query_start;
-    }
-  }
-  
-  p= sql_script;
-  query_start= p;
-  
-  while (*p)
-  {
-    if (p[0] == ';' && p[1] == '\n')
-    {
-      size_t query_len= p - query_start;
-      const char *q= query_start;
-      const char *q_end= query_start + query_len;
-      
-      while (q < q_end && my_isspace(charset_info, *q))
-        q++;
-      
-      if (q < q_end)
-      {
-        my_bool is_last= (query_start == last_query_start && 
-                          query_len == last_query_len);
+        /* Check if this is EXPLAIN FORMAT=JSON */
+        my_bool is_explain= is_explain_format_json(query_start, query_len);
         
         verbose_msg("ReplayTest: Executing query on replay server (%s): %.*s",
-                    is_last ? "LAST" : "intermediate", (int)query_len, query_start);
+                    is_explain ? "EXPLAIN - will stop after this" : "intermediate",
+                    (int)query_len, query_start);
         
+        /* Execute the query */
         if (mysql_real_query(replay_server_mysql, query_start, query_len))
         {
           fprintf(stdout, "ReplayTest: Query failed on replay server: %d %s\n",
                   mysql_errno(replay_server_mysql),
                   mysql_error(replay_server_mysql));
           fprintf(stdout, "ReplayTest: Failed query was: %.*s\n", (int)query_len, query_start);
-          dynstr_free(&last_result);
+          dynstr_free(&result);
           DBUG_VOID_RETURN;
         }
         
+        /* Process results */
         do
         {
           MYSQL_RES *res= mysql_store_result(replay_server_mysql);
           if (res)
           {
-            if (is_last)
+            /* Capture output only if this is EXPLAIN FORMAT=JSON */
+            if (is_explain)
             {
               MYSQL_FIELD *fields= mysql_fetch_fields(res);
               uint num_fields= mysql_num_fields(res);
@@ -8510,7 +8473,7 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
               
               if (!display_result_vertically)
               {
-                append_table_headings(&last_result, fields, num_fields);
+                append_table_headings(&result, fields, num_fields);
               }
               
               while ((row= mysql_fetch_row(res)))
@@ -8518,15 +8481,23 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
                 uint i;
                 ulong *lengths= mysql_fetch_lengths(res);
                 for (i= 0; i < num_fields; i++)
-                  append_field(&last_result, i, &fields[i],
+                  append_field(&result, i, &fields[i],
                               row[i], lengths[i], !row[i]);
                 if (!display_result_vertically)
-                  dynstr_append_mem(&last_result, "\n", 1);
+                  dynstr_append_mem(&result, "\n", 1);
               }
             }
             mysql_free_result(res);
           }
         } while (mysql_next_result(replay_server_mysql) == 0);
+        
+        /* If this was EXPLAIN, we're done - stop processing */
+        if (is_explain)
+        {
+          found_explain= TRUE;
+          verbose_msg("ReplayTest: Found EXPLAIN FORMAT=JSON, stopping script execution");
+          break;
+        }
       }
       
       p += 2;
@@ -8538,7 +8509,8 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
     }
   }
   
-  if (query_start < p)
+  /* Handle final query if we haven't found EXPLAIN yet */
+  if (!found_explain && query_start < p)
   {
     const char *q= query_start;
     const char *q_end= p;
@@ -8547,8 +8519,10 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
     if (q < q_end)
     {
       size_t query_len= p - query_start;
+      my_bool is_explain= is_explain_format_json(query_start, query_len);
       
-      verbose_msg("ReplayTest: Executing final query on replay server: %.*s",
+      verbose_msg("ReplayTest: Executing final query on replay server (%s): %.*s",
+                  is_explain ? "EXPLAIN" : "last query",
                   (int)query_len, query_start);
       
       if (mysql_real_query(replay_server_mysql, query_start, query_len))
@@ -8557,7 +8531,7 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
                 mysql_errno(replay_server_mysql),
                 mysql_error(replay_server_mysql));
         fprintf(stdout, "ReplayTest: Failed query was: %.*s\n", (int)query_len, query_start);
-        dynstr_free(&last_result);
+        dynstr_free(&result);
         DBUG_VOID_RETURN;
       }
       
@@ -8572,7 +8546,7 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
           
           if (!display_result_vertically)
           {
-            append_table_headings(&last_result, fields, num_fields);
+            append_table_headings(&result, fields, num_fields);
           }
           
           while ((row= mysql_fetch_row(res)))
@@ -8580,19 +8554,27 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
             uint i;
             ulong *lengths= mysql_fetch_lengths(res);
             for (i= 0; i < num_fields; i++)
-              append_field(&last_result, i, &fields[i],
+              append_field(&result, i, &fields[i],
                           row[i], lengths[i], !row[i]);
             if (!display_result_vertically)
-              dynstr_append_mem(&last_result, "\n", 1);
+              dynstr_append_mem(&result, "\n", 1);
           }
           mysql_free_result(res);
         }
       } while (mysql_next_result(replay_server_mysql) == 0);
+      
+      if (is_explain)
+        found_explain= TRUE;
     }
   }
   
-  dynstr_append_mem(ds, last_result.str, last_result.length);
-  dynstr_free(&last_result);
+  if (!found_explain)
+  {
+    verbose_msg("ReplayTest: Warning - no EXPLAIN FORMAT=JSON found in script");
+  }
+  
+  dynstr_append_mem(ds, result.str, result.length);
+  dynstr_free(&result);
   DBUG_VOID_RETURN;
 }
 
diff --git a/mysql-test/main/replay_server_test.test b/mysql-test/main/replay_server_test.test
index a126bc545ed40..7008d84991dc5 100644
--- a/mysql-test/main/replay_server_test.test
+++ b/mysql-test/main/replay_server_test.test
@@ -41,6 +41,7 @@ EOF
 # Test ReplayTest mode with EXPLAIN FORMAT=JSON
 CREATE TABLE t1 (a INT, b INT, KEY(a));
 INSERT INTO t1 VALUES (1,1), (2,2), (3,3);
+analyze table t1;
 
 # This should trigger ReplayTest mode if REPLAY_SERVER_SOCKET is set
 EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE a = 1;

From 95b6b5ee8d740ade1f219c65ff82289106a4ad89 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Mon, 20 Apr 2026 13:08:45 +0300
Subject: [PATCH 04/50] MDEV-39368: Make mtr write queries into
 log/replay_queries.log

---
 client/mysqltest.cc | 70 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index a0d011d180624..3cd451e3926ef 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -275,6 +275,8 @@ static size_t suite_dir_len, overlay_dir_len;
 static MYSQL *replay_server_mysql= NULL;
 static const char *replay_server_socket= NULL;
 static my_bool replay_test_mode= FALSE;
+static FILE *replay_log_file= NULL;
+static const char *replay_log_path= NULL;
 
 /* Precompiled re's */
 static regex_t ps_re;     /* the query can be run using PS protocol */
@@ -1517,6 +1519,18 @@ void free_used_memory()
     replay_server_mysql= NULL;
   }
 
+  if (replay_log_file)
+  {
+    fclose(replay_log_file);
+    replay_log_file= NULL;
+  }
+
+  if (replay_log_path)
+  {
+    my_free((void*)replay_log_path);
+    replay_log_path= NULL;
+  }
+
   if (connections)
   {
     close_connections();
@@ -8408,6 +8422,30 @@ static my_bool is_explain_format_json(const char *query, size_t query_len)
   return TRUE;
 }
 
+/*
+  Log the start of a new replay session
+*/
+static void log_replay_session_start()
+{
+  if (replay_log_file)
+  {
+    fprintf(replay_log_file, "### REPLAY SESSION ###\n");
+    fflush(replay_log_file);
+  }
+}
+
+/*
+  Log a query being sent to the replay server
+*/
+static void log_replay_query(const char *query, size_t query_len)
+{
+  if (replay_log_file)
+  {
+    fprintf(replay_log_file, "%.*s;\n", (int)query_len, query);
+    fflush(replay_log_file);
+  }
+}
+
 /*
   Execute queries from SQL script on replay server
   Split by ";\n" and execute each query
@@ -8423,6 +8461,8 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
   
   verbose_msg("ReplayTest: SQL script from optimizer_context:\n%s", sql_script);
   
+  log_replay_session_start();
+  
   init_dynamic_string(&result, "", 1024, 1024);
   
   /* Single-pass execution: stop at first EXPLAIN FORMAT=JSON */
@@ -8447,6 +8487,9 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
                     is_explain ? "EXPLAIN - will stop after this" : "intermediate",
                     (int)query_len, query_start);
         
+        /* Log the query */
+        log_replay_query(query_start, query_len);
+        
         /* Execute the query */
         if (mysql_real_query(replay_server_mysql, query_start, query_len))
         {
@@ -8525,6 +8568,9 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
                   is_explain ? "EXPLAIN" : "last query",
                   (int)query_len, query_start);
       
+      /* Log the query */
+      log_replay_query(query_start, query_len);
+      
       if (mysql_real_query(replay_server_mysql, query_start, query_len))
       {
         fprintf(stdout, "ReplayTest: Query failed on replay server: %d %s\n",
@@ -10646,6 +10692,30 @@ int main(int argc, char **argv)
     replay_test_mode= TRUE;
     verbose_msg("ReplayTest mode enabled, replay server socket: %s", 
                 replay_server_socket);
+    
+    /* Initialize replay query log file */
+    const char *vardir= getenv("MYSQLTEST_VARDIR");
+    if (vardir)
+    {
+      size_t path_len= strlen(vardir) + 30;  /* room for "/log/replay_queries.log" */
+      char *log_path= (char*)my_malloc(PSI_NOT_INSTRUMENTED, path_len, MYF(0));
+      if (log_path)
+      {
+        snprintf(log_path, path_len, "%s/log/replay_queries.log", vardir);
+        replay_log_path= log_path;
+        /* Use append mode - MTR cleans var directory on each run */
+        replay_log_file= fopen(replay_log_path, "a");
+        if (!replay_log_file)
+        {
+          fprintf(stderr, "Warning: Could not open replay log file: %s\n", 
+                  replay_log_path);
+        }
+        else
+        {
+          verbose_msg("ReplayTest: Logging queries to %s", replay_log_path);
+        }
+      }
+    }
   }
 
   /* Cursor protocol implies ps protocol */

From 8aee7b2d45fc49ac24358ea0a07a93c3ca9c2f73 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Mon, 20 Apr 2026 15:13:02 +0300
Subject: [PATCH 05/50] MDEV-39368: Run set optimizer_replay_context='' for
 cleanup.

---
 client/mysqltest.cc                     | 33 +++++++++++++++++++++----
 mysql-test/main/replay_server_test.test |  2 ++
 2 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index 3cd451e3926ef..f46419c25eae5 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -8497,8 +8497,7 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
                   mysql_errno(replay_server_mysql),
                   mysql_error(replay_server_mysql));
           fprintf(stdout, "ReplayTest: Failed query was: %.*s\n", (int)query_len, query_start);
-          dynstr_free(&result);
-          DBUG_VOID_RETURN;
+          goto cleanup;
         }
         
         /* Process results */
@@ -8577,8 +8576,7 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
                 mysql_errno(replay_server_mysql),
                 mysql_error(replay_server_mysql));
         fprintf(stdout, "ReplayTest: Failed query was: %.*s\n", (int)query_len, query_start);
-        dynstr_free(&result);
-        DBUG_VOID_RETURN;
+        goto cleanup;
       }
       
       do
@@ -8618,9 +8616,34 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
   {
     verbose_msg("ReplayTest: Warning - no EXPLAIN FORMAT=JSON found in script");
   }
-  
+
+cleanup:
+  /* Preserve accumulated output (EXPLAIN / last-query) in ds BEFORE cleanup query */
   dynstr_append_mem(ds, result.str, result.length);
   dynstr_free(&result);
+
+  /* Reset optimizer_replay_context on the replay server, regardless of errors.
+     Drain and discard any output so ds is not affected. */
+  if (replay_server_mysql)
+  {
+    if (mysql_real_query(replay_server_mysql,
+                         "set optimizer_replay_context=''", 31))
+    {
+      fprintf(stdout, "ReplayTest: Warning - failed to reset optimizer_replay_context: %d %s\n",
+              mysql_errno(replay_server_mysql),
+              mysql_error(replay_server_mysql));
+    }
+    else
+    {
+      do
+      {
+        MYSQL_RES *res= mysql_store_result(replay_server_mysql);
+        if (res)
+          mysql_free_result(res);
+      } while (mysql_next_result(replay_server_mysql) == 0);
+    }
+  }
+
   DBUG_VOID_RETURN;
 }
 
diff --git a/mysql-test/main/replay_server_test.test b/mysql-test/main/replay_server_test.test
index 7008d84991dc5..7b4617a1f4369 100644
--- a/mysql-test/main/replay_server_test.test
+++ b/mysql-test/main/replay_server_test.test
@@ -46,4 +46,6 @@ analyze table t1;
 # This should trigger ReplayTest mode if REPLAY_SERVER_SOCKET is set
 EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE a = 1;
 
+EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE a < 100;
+
 DROP TABLE t1;

From cf5615b8a9003a0359390f3cad847f893d740287 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Mon, 20 Apr 2026 18:06:58 +0300
Subject: [PATCH 06/50] Don't display result column name twice.

---
 client/mysqltest.cc | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index f46419c25eae5..75d20d8f6eb0a 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -8780,7 +8780,9 @@ void run_query_normal(struct st_connection *cn, struct st_command *command,
 	if (display_metadata)
           append_metadata(ds, fields, num_fields);
 
-	if (!display_result_vertically)
+	/* In replay mode, headings come from the replay server's result */
+	if (!display_result_vertically &&
+	    !(replay_mode_active && counter == 0))
 	  append_table_headings(ds, fields, num_fields);
 
 	/* ReplayTest mode: Replace EXPLAIN result with replay server output */

From 4a60f86e7e3009d9cc92ee31edd4ac4cca9d6f59 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Mon, 20 Apr 2026 18:08:13 +0300
Subject: [PATCH 07/50] Kill replay server when mtr exits, in various cases.

---
 mysql-test/mariadb-test-run.pl | 58 ++++++++++++++++++++++++++++------
 1 file changed, 48 insertions(+), 10 deletions(-)

diff --git a/mysql-test/mariadb-test-run.pl b/mysql-test/mariadb-test-run.pl
index de4e3347b44bf..6216d0f4026d0 100755
--- a/mysql-test/mariadb-test-run.pl
+++ b/mysql-test/mariadb-test-run.pl
@@ -150,6 +150,11 @@ BEGIN
 
 our @global_suppressions;
 
+# Forward declarations for variables referenced in END block
+our $opt_replay_server;
+our $opt_replay_server_manual;
+our $replay_server_parent_pid;  # PID of process that started the replay server
+
 END {
   if ( defined $opt_tmpdir_pid and $opt_tmpdir_pid == $$ )
   {
@@ -164,6 +169,15 @@ END
       mtr_warning("tmpdir $opt_tmpdir should be removed after the server has finished");
     }
   }
+
+  # Ensure replay server is stopped on any exit path (success or failure).
+  # Only run in the parent process that started it; safe to call even if
+  # already stopped (stop_replay_server clears REPLAY_SERVER_PID).
+  if (defined $replay_server_parent_pid and $replay_server_parent_pid == $$
+      and ($opt_replay_server || $opt_replay_server_manual))
+  {
+    eval { stop_replay_server(); };
+  }
 }
 
 sub env_or_val($$) { defined $ENV{$_[0]} ? $ENV{$_[0]} : $_[1] }
@@ -3049,9 +3063,21 @@ sub initialize_servers {
 }
 
 
+sub _install_replay_server_signal_handlers {
+  # Ensure END block (which stops the replay server) runs on common
+  # termination signals. Perl END blocks don't run on uncaught signals;
+  # installing handlers that call exit() lets them run.
+  for my $sig (qw(INT TERM HUP)) {
+    $SIG{$sig} = sub { exit(1); };
+  }
+}
+
+
 sub start_replay_server {
   mtr_report("Starting replay server...");
-  
+  $replay_server_parent_pid = $$;
+  _install_replay_server_signal_handlers();
+
   my $replay_server_num = 1;
   my $script = "$glob_mysql_test_dir/lib/start_extra_server.pl";
   
@@ -3104,7 +3130,9 @@ sub start_replay_server {
 
 sub start_replay_server_manual {
   mtr_report("Starting replay server in manual mode...");
-  
+  $replay_server_parent_pid = $$;
+  _install_replay_server_signal_handlers();
+
   my $replay_server_num = 1;
   
   # Set required environment variables
@@ -3260,30 +3288,40 @@ sub stop_replay_server {
   
   my $pid = $ENV{REPLAY_SERVER_PID};
   
-  # Send SIGTERM
+  # Send SIGTERM. The replay server is NOT a direct child of this process
+  # (start_extra_server.pl is an intermediate), so waitpid() cannot be used
+  # to poll its exit status. Use `kill 0, $pid` (signal 0 - existence check)
+  # instead.
   if (kill 0, $pid) {
     kill 'TERM', $pid;
-    
+
     # Wait for process to exit (up to 10 seconds)
     my $max_wait = 10;
     my $waited = 0;
-    while ($waited < $max_wait) {
-      my $result = waitpid($pid, WNOHANG);
-      last if ($result == $pid || $result == -1);
+    while ($waited < $max_wait && kill(0, $pid)) {
       sleep 1;
       $waited++;
     }
-    
+
     # Force kill if still running
-    if ($waited >= $max_wait && kill 0, $pid) {
+    if (kill 0, $pid) {
       kill 'KILL', $pid;
+      # Wait briefly for KILL to take effect
+      my $kill_waited = 0;
+      while ($kill_waited < 3 && kill(0, $pid)) {
+        sleep 1;
+        $kill_waited++;
+      }
     }
   }
   
   # Cleanup info file
   my $info_file = "$opt_vardir/tmp/extra_server_1.info";
   unlink $info_file if -f $info_file;
-  
+
+  # Mark as stopped so subsequent calls (e.g. from END block) are no-ops
+  delete $ENV{REPLAY_SERVER_PID};
+
   mtr_report("Replay server stopped");
 }
 

From 0eb9e92bb8039a20d12c84d791dd0afc7286e372 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Mon, 20 Apr 2026 18:09:10 +0300
Subject: [PATCH 08/50] Let the optimizer context have DROP TABLE|VIEW IF
 EXISTS.

This is needed to be able to run replay for many queries in a row.
Need to discuss whether we should ship it like this.
---
 .../main/opt_context_replay_basic.result      |  3 ++
 .../opt_context_replay_innodb_comp.result     | 28 +++++++++++++++++++
 .../opt_context_replay_innodb_pref.result     | 28 +++++++++++++++++++
 mysql-test/main/opt_context_store_ddls.result | 12 ++++++++
 mysql-test/main/replay_server_test.test       |  5 +++-
 sql/opt_context_store_replay.cc               | 14 ++++++++++
 6 files changed, 89 insertions(+), 1 deletion(-)

diff --git a/mysql-test/main/opt_context_replay_basic.result b/mysql-test/main/opt_context_replay_basic.result
index 29107d5a98cbb..33b483fee625c 100644
--- a/mysql-test/main/opt_context_replay_basic.result
+++ b/mysql-test/main/opt_context_replay_basic.result
@@ -121,6 +121,9 @@ CREATE DATABASE IF NOT EXISTS db1;
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
 USE db1;
+DROP TABLE IF EXISTS db1.t1;
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 CREATE TABLE `t1` (
 `a` int(11) DEFAULT NULL,
 `b` int(11) DEFAULT NULL,
diff --git a/mysql-test/main/opt_context_replay_innodb_comp.result b/mysql-test/main/opt_context_replay_innodb_comp.result
index fa52d874df565..07bd83d0484c7 100644
--- a/mysql-test/main/opt_context_replay_innodb_comp.result
+++ b/mysql-test/main/opt_context_replay_innodb_comp.result
@@ -106,6 +106,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -228,6 +230,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -345,6 +349,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -466,6 +472,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -591,6 +599,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -712,6 +722,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -818,6 +830,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -914,6 +928,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -992,6 +1008,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -1079,6 +1097,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -1164,6 +1184,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -1248,6 +1270,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -1357,6 +1381,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -1491,6 +1517,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
diff --git a/mysql-test/main/opt_context_replay_innodb_pref.result b/mysql-test/main/opt_context_replay_innodb_pref.result
index dd5d733f2ab7d..cd0f952e75464 100644
--- a/mysql-test/main/opt_context_replay_innodb_pref.result
+++ b/mysql-test/main/opt_context_replay_innodb_pref.result
@@ -106,6 +106,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -228,6 +230,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -345,6 +349,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -466,6 +472,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -591,6 +599,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -712,6 +722,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -818,6 +830,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -914,6 +928,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -992,6 +1008,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -1079,6 +1097,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -1164,6 +1184,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -1248,6 +1270,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -1357,6 +1381,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
@@ -1491,6 +1517,8 @@ Warnings:
 Warning	4200	The setting 'optimizer_adjust_secondary_key_costs' is ignored. It only exists for compatibility with old installations and will be removed in a future release
 Warnings:
 Note	1007	Can't create database 'db1'; database exists
+Warnings:
+Note	1051	Unknown table 'db1.t1'
 EXPLAIN
 {
   "query_block": {
diff --git a/mysql-test/main/opt_context_store_ddls.result b/mysql-test/main/opt_context_store_ddls.result
index d005edb966128..9eaaf82d0dba7 100644
--- a/mysql-test/main/opt_context_store_ddls.result
+++ b/mysql-test/main/opt_context_store_ddls.result
@@ -145,11 +145,13 @@ CREATE TABLE `t2` (
   `a` int(11) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci;
 
+DROP TABLE IF EXISTS db1.t1;
 CREATE TABLE `t1` (
   `a` int(11) DEFAULT NULL,
   `b` int(11) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci;
 
+DROP VIEW IF EXISTS db1.view1;
 CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW db1.view1 AS (select `db1`.`t1`.`a` AS `a`,`db1`.`t1`.`b` AS `b`,`db1`.`t2`.`a` AS `c` from (`db1`.`t1` join `db1`.`t2`) where `db1`.`t1`.`a` = `db1`.`t2`.`a`);
 
 
@@ -180,6 +182,7 @@ CREATE TABLE `t2` (
   `a` int(11) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci;
 
+DROP TABLE IF EXISTS db1.temp1;
 CREATE TEMPORARY TABLE `temp1` (
   `col1` int(11) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci;
@@ -241,11 +244,13 @@ CREATE TABLE `t2` (
   `a` int(11) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci;
 
+DROP TABLE IF EXISTS db1.t1;
 CREATE TABLE `t1` (
   `a` int(11) DEFAULT NULL,
   `b` int(11) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci;
 
+DROP VIEW IF EXISTS db1.view1;
 CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW db1.view1 AS (select `db1`.`t1`.`a` AS `a`,`db1`.`t1`.`b` AS `b`,`db1`.`t2`.`a` AS `c` from (`db1`.`t1` join `db1`.`t2`) where `db1`.`t1`.`a` = `db1`.`t2`.`a`);
 
 
@@ -350,6 +355,7 @@ CREATE TABLE `t2` (
   `a` int(11) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci;
 
+DROP TABLE IF EXISTS db1.t1;
 CREATE TABLE `t1` (
   `a` int(11) DEFAULT NULL,
   `b` int(11) DEFAULT NULL
@@ -391,6 +397,7 @@ CREATE TABLE `db2`.`t1` (
   `a` int(11) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci;
 
+DROP TABLE IF EXISTS db1.t1;
 CREATE TABLE `t1` (
   `a` int(11) DEFAULT NULL,
   `b` int(11) DEFAULT NULL
@@ -430,6 +437,7 @@ CREATE TABLE `t1` (
 
 CREATE DATABASE IF NOT EXISTS db1;
 
+DROP TABLE IF EXISTS db1.t1;
 CREATE TABLE `db1`.`t1` (
   `a` int(11) DEFAULT NULL,
   `b` int(11) DEFAULT NULL
@@ -509,6 +517,7 @@ CREATE TABLE `t2` (
 
 REPLACE INTO db1.t2(a, b) VALUES (1, 1);
 
+DROP TABLE IF EXISTS db1.t1;
 CREATE TABLE `t1` (
   `a` int(11) DEFAULT NULL,
   `b` int(11) DEFAULT NULL
@@ -670,6 +679,7 @@ CREATE TABLE `t2` (
   KEY `fk_id` (`id`)
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci;
 
+DROP TABLE IF EXISTS db1.t1;
 CREATE TABLE `t1` (
   `id` int(11) NOT NULL AUTO_INCREMENT,
   `name` varchar(10) DEFAULT NULL,
@@ -709,6 +719,7 @@ CREATE TABLE `t2` (
   `id2` int(11) NOT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci;
 
+DROP TABLE IF EXISTS db1.t1;
 CREATE TABLE `t1` (
   `id1` int(11) NOT NULL AUTO_INCREMENT,
   PRIMARY KEY (`id1`)
@@ -740,6 +751,7 @@ CREATE TABLE `t2` (
   `id2` int(11) NOT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci;
 
+DROP TABLE IF EXISTS db1.t1;
 CREATE TABLE `t1` (
   `id1` int(11) NOT NULL AUTO_INCREMENT,
   PRIMARY KEY (`id1`)
diff --git a/mysql-test/main/replay_server_test.test b/mysql-test/main/replay_server_test.test
index 7b4617a1f4369..a5399a1517c26 100644
--- a/mysql-test/main/replay_server_test.test
+++ b/mysql-test/main/replay_server_test.test
@@ -46,6 +46,9 @@ analyze table t1;
 # This should trigger ReplayTest mode if REPLAY_SERVER_SOCKET is set
 EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE a = 1;
 
-EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE a < 100;
+EXPLAIN FORMAT=JSON
+SELECT * FROM t1 WHERE a < 100;
+
+SELECT * FROM t1 WHERE a < 100;
 
 DROP TABLE t1;
diff --git a/sql/opt_context_store_replay.cc b/sql/opt_context_store_replay.cc
index 9b4f40a67526a..50a7374dde6be 100644
--- a/sql/opt_context_store_replay.cc
+++ b/sql/opt_context_store_replay.cc
@@ -613,9 +613,23 @@ bool store_optimizer_context(THD *thd)
     }
 
     if (tbl->is_view())
+    {
+      StringBuffer<64> drop;
+      drop.append(STRING_WITH_LEN("DROP VIEW IF EXISTS "));
+      drop.append(full_tbl_name);
+      drop.append(STRING_WITH_LEN(";\n"));
+      sql_script.append(drop);
+      
       create_view_def(thd, tbl, &full_tbl_name, &ddl);
+    }
     else
     {
+      StringBuffer<64> drop;
+      drop.append(STRING_WITH_LEN("DROP TABLE IF EXISTS "));
+      drop.append(full_tbl_name);
+      drop.append(STRING_WITH_LEN(";\n"));
+      sql_script.append(drop);
+
       if (show_create_table(thd, tbl, &ddl, NULL, WITH_DB_NAME))
       {
         res= true;

From c9bca52de8124dcdf137c92500b5333e15a44381 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Tue, 21 Apr 2026 13:40:51 +0300
Subject: [PATCH 09/50] Temporarily? disable assert for DBUG_ASSERT(*freq > 0)
 in infuse_table_stats

---
 sql/opt_context_store_replay.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sql/opt_context_store_replay.cc b/sql/opt_context_store_replay.cc
index 50a7374dde6be..ec0a01944d600 100644
--- a/sql/opt_context_store_replay.cc
+++ b/sql/opt_context_store_replay.cc
@@ -1706,7 +1706,8 @@ void Optimizer_context_replay::infuse_table_stats(TABLE *table)
 
         while (freq && i < num_key_parts)
         {
-          DBUG_ASSERT(*freq > 0);
+          // Apparently this can be=0 for prefix indexes.
+          //DBUG_ASSERT(*freq > 0);
           key_info->read_stats->set_avg_frequency(i, (double) *freq);
           freq= li++;
           i++;

From 35437c6e96f2491ff1dad91e73d1c0caf3d58af3 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Tue, 21 Apr 2026 13:49:37 +0300
Subject: [PATCH 10/50] Enable replay for any EXPLAIN query, do not require
 "FORMAT=JSON".

---
 client/mysqltest.cc                       |  5 +-
 mysql-test/main/replay_server_test.result | 72 +++++++++++++++++++++++
 mysql-test/main/replay_server_test.test   |  6 ++
 3 files changed, 81 insertions(+), 2 deletions(-)
 create mode 100644 mysql-test/main/replay_server_test.result

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index 75d20d8f6eb0a..3c1907c55a60e 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -8398,7 +8398,8 @@ static my_bool is_explain_format_json(const char *query, size_t query_len)
   
   if (p >= end || !my_isspace(charset_info, *p))
     return FALSE;
-  
+/*
+  (Don't requre FORMAT=JSON)
   while (p < end && my_isspace(charset_info, *p))
     p++;
   
@@ -8418,7 +8419,7 @@ static my_bool is_explain_format_json(const char *query, size_t query_len)
   
   if (end - p < 4 || strncasecmp(p, "JSON", 4) != 0)
     return FALSE;
-  
+*/
   return TRUE;
 }
 
diff --git a/mysql-test/main/replay_server_test.result b/mysql-test/main/replay_server_test.result
new file mode 100644
index 0000000000000..7439ca0436d8a
--- /dev/null
+++ b/mysql-test/main/replay_server_test.result
@@ -0,0 +1,72 @@
+REPLAY_SERVER_SOCKET is NOT set
+CREATE TABLE t1 (a INT, b INT, KEY(a));
+INSERT INTO t1 VALUES (1,1), (2,2), (3,3);
+analyze table t1;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	Engine-independent statistics collected
+test.t1	analyze	status	OK
+EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE a = 1;
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "cost": 0.002024411,
+    "nested_loop": [
+      {
+        "table": {
+          "table_name": "t1",
+          "access_type": "ref",
+          "possible_keys": ["a"],
+          "key": "a",
+          "key_length": "5",
+          "used_key_parts": ["a"],
+          "ref": ["const"],
+          "loops": 1,
+          "rows": 1,
+          "cost": 0.002024411,
+          "filtered": 100
+        }
+      }
+    ]
+  }
+}
+EXPLAIN FORMAT=JSON
+SELECT * FROM t1 WHERE a < 100;
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "cost": 0.005042291,
+    "nested_loop": [
+      {
+        "table": {
+          "table_name": "t1",
+          "access_type": "range",
+          "possible_keys": ["a"],
+          "key": "a",
+          "key_length": "5",
+          "used_key_parts": ["a"],
+          "loops": 1,
+          "rows": 3,
+          "cost": 0.005042291,
+          "filtered": 100,
+          "index_condition": "t1.a < 100"
+        }
+      }
+    ]
+  }
+}
+SELECT * FROM t1 WHERE a < 100;
+a	b
+1	1
+2	2
+3	3
+explain
+SELECT * FROM t1 WHERE a < 22;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	a	a	5	NULL	3	Using index condition
+explain
+SELECT * FROM t1 WHERE b < 22;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+DROP TABLE t1;
diff --git a/mysql-test/main/replay_server_test.test b/mysql-test/main/replay_server_test.test
index a5399a1517c26..264ea92034b1f 100644
--- a/mysql-test/main/replay_server_test.test
+++ b/mysql-test/main/replay_server_test.test
@@ -51,4 +51,10 @@ SELECT * FROM t1 WHERE a < 100;
 
 SELECT * FROM t1 WHERE a < 100;
 
+explain
+SELECT * FROM t1 WHERE a < 22;
+
+explain
+SELECT * FROM t1 WHERE b < 22;
+
 DROP TABLE t1;

From cb9310fb8e0d6609687e6092605c0066be988eb6 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Wed, 22 Apr 2026 14:55:12 +0300
Subject: [PATCH 11/50] Remove garbage comment

---
 client/mysqltest.cc | 23 +----------------------
 1 file changed, 1 insertion(+), 22 deletions(-)

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index 3c1907c55a60e..e470fc8631962 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -8398,28 +8398,7 @@ static my_bool is_explain_format_json(const char *query, size_t query_len)
   
   if (p >= end || !my_isspace(charset_info, *p))
     return FALSE;
-/*
-  (Don't requre FORMAT=JSON)
-  while (p < end && my_isspace(charset_info, *p))
-    p++;
-  
-  if (end - p < 6 || strncasecmp(p, "FORMAT", 6) != 0)
-    return FALSE;
-  p += 6;
-  
-  while (p < end && my_isspace(charset_info, *p))
-    p++;
-  
-  if (p >= end || *p != '=')
-    return FALSE;
-  p++;
-  
-  while (p < end && my_isspace(charset_info, *p))
-    p++;
-  
-  if (end - p < 4 || strncasecmp(p, "JSON", 4) != 0)
-    return FALSE;
-*/
+
   return TRUE;
 }
 

From a8e4c7cbee0ae3cfb1573977af127b55385e71db Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Wed, 22 Apr 2026 15:02:01 +0300
Subject: [PATCH 12/50] MDEV-39368: Do not try to replay EXPLAIN FOR CONNECTION

---
 client/mysqltest.cc | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index e470fc8631962..47d1dea3c13a3 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -8381,10 +8381,12 @@ static int ensure_replay_server_connection()
 }
 
 /*
-  Check if query starts with "EXPLAIN FORMAT=JSON"
-  Returns TRUE if it matches, FALSE otherwise
+  Check if query starts with "EXPLAIN"
+  Returns TRUE if it matches, FALSE otherwise.
+  Returns FALSE for "EXPLAIN FOR ..." (e.g. EXPLAIN FOR CONNECTION), since that
+  form does not trigger query optimization/recording.
 */
-static my_bool is_explain_format_json(const char *query, size_t query_len)
+static my_bool is_explain_query(const char *query, size_t query_len)
 {
   const char *p= query;
   const char *end= query + query_len;
@@ -8399,6 +8401,15 @@ static my_bool is_explain_format_json(const char *query, size_t query_len)
   if (p >= end || !my_isspace(charset_info, *p))
     return FALSE;
 
+  /* Skip whitespace between EXPLAIN and the next token */
+  while (p < end && my_isspace(charset_info, *p))
+    p++;
+
+  /* Reject "EXPLAIN FOR ..." (token "FOR" followed by whitespace or end) */
+  if (end - p >= 3 && strncasecmp(p, "FOR", 3) == 0 &&
+      (end - p == 3 || my_isspace(charset_info, p[3])))
+    return FALSE;
+
   return TRUE;
 }
 
@@ -8461,7 +8472,7 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
       if (q < q_end)
       {
         /* Check if this is EXPLAIN FORMAT=JSON */
-        my_bool is_explain= is_explain_format_json(query_start, query_len);
+        my_bool is_explain= is_explain_query(query_start, query_len);
         
         verbose_msg("ReplayTest: Executing query on replay server (%s): %.*s",
                     is_explain ? "EXPLAIN - will stop after this" : "intermediate",
@@ -8541,7 +8552,7 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
     if (q < q_end)
     {
       size_t query_len= p - query_start;
-      my_bool is_explain= is_explain_format_json(query_start, query_len);
+      my_bool is_explain= is_explain_query(query_start, query_len);
       
       verbose_msg("ReplayTest: Executing final query on replay server (%s): %.*s",
                   is_explain ? "EXPLAIN" : "last query",
@@ -8686,7 +8697,7 @@ void run_query_normal(struct st_connection *cn, struct st_command *command,
 
   /* ReplayTest mode: Set optimizer_record_context BEFORE sending EXPLAIN query */
   if (replay_test_mode && (flags & QUERY_SEND_FLAG) && (flags & QUERY_REAP_FLAG) &&
-      is_explain_format_json(query, query_len))
+      is_explain_query(query, query_len))
   {
     replay_mode_active= TRUE;
     verbose_msg("ReplayTest: Detected EXPLAIN FORMAT=JSON query, activating replay mode");

From f4b6b7302fa022e621141e3d46d720559f2a0d38 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Wed, 22 Apr 2026 15:10:05 +0300
Subject: [PATCH 13/50] MDEV-39368: Print warnings for replay EXPLAINs.

---
 client/mysqltest.cc                       | 30 +++++++++++++++++++++--
 mysql-test/main/replay_server_test.result |  6 +++++
 mysql-test/main/replay_server_test.test   |  3 +++
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index 47d1dea3c13a3..a668bbb2fd7b9 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -8523,7 +8523,20 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
             mysql_free_result(res);
           }
         } while (mysql_next_result(replay_server_mysql) == 0);
-        
+
+        /* Collect warnings from the EXPLAIN query (replay server) */
+        if (is_explain && !disable_warnings)
+        {
+          DYNAMIC_STRING ds_warn;
+          init_dynamic_string(&ds_warn, "", 256, 256);
+          if (append_warnings(&ds_warn, replay_server_mysql) || ds_warn.length)
+          {
+            dynstr_append_mem(&result, "Warnings:\n", 10);
+            dynstr_append_mem(&result, ds_warn.str, ds_warn.length);
+          }
+          dynstr_free(&ds_warn);
+        }
+
         /* If this was EXPLAIN, we're done - stop processing */
         if (is_explain)
         {
@@ -8597,7 +8610,20 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
           mysql_free_result(res);
         }
       } while (mysql_next_result(replay_server_mysql) == 0);
-      
+
+      /* Collect warnings from the EXPLAIN query (replay server) */
+      if (is_explain && !disable_warnings)
+      {
+        DYNAMIC_STRING ds_warn;
+        init_dynamic_string(&ds_warn, "", 256, 256);
+        if (append_warnings(&ds_warn, replay_server_mysql) || ds_warn.length)
+        {
+          dynstr_append_mem(&result, "Warnings:\n", 10);
+          dynstr_append_mem(&result, ds_warn.str, ds_warn.length);
+        }
+        dynstr_free(&ds_warn);
+      }
+
       if (is_explain)
         found_explain= TRUE;
     }
diff --git a/mysql-test/main/replay_server_test.result b/mysql-test/main/replay_server_test.result
index 7439ca0436d8a..f28194679d07c 100644
--- a/mysql-test/main/replay_server_test.result
+++ b/mysql-test/main/replay_server_test.result
@@ -65,6 +65,12 @@ explain
 SELECT * FROM t1 WHERE a < 22;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	a	a	5	NULL	3	Using index condition
+explain extended
+SELECT * FROM t1 WHERE a < 22;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	range	a	a	5	NULL	3	100.00	Using index condition
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where `test`.`t1`.`a` < 22
 explain
 SELECT * FROM t1 WHERE b < 22;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
diff --git a/mysql-test/main/replay_server_test.test b/mysql-test/main/replay_server_test.test
index 264ea92034b1f..178fac64e3613 100644
--- a/mysql-test/main/replay_server_test.test
+++ b/mysql-test/main/replay_server_test.test
@@ -54,6 +54,9 @@ SELECT * FROM t1 WHERE a < 100;
 explain
 SELECT * FROM t1 WHERE a < 22;
 
+explain extended
+SELECT * FROM t1 WHERE a < 22;
+
 explain
 SELECT * FROM t1 WHERE b < 22;
 

From 5156d71b7c0dab92291aac7db21eb5709920951f Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Wed, 22 Apr 2026 15:20:35 +0300
Subject: [PATCH 14/50] MDEV-39368: Refuse to run with --replay-server and
 --parallel

---
 mysql-test/mariadb-test-run.pl | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/mysql-test/mariadb-test-run.pl b/mysql-test/mariadb-test-run.pl
index 6216d0f4026d0..dbdc7f9b42756 100755
--- a/mysql-test/mariadb-test-run.pl
+++ b/mysql-test/mariadb-test-run.pl
@@ -295,8 +295,8 @@ END
 our $opt_gprof;
 our %gprof_dirs;
 
-our $opt_replay_server;  # Start an extra server for replay
-our $opt_replay_server_manual;  # Print replay server command and wait for manual start
+# $opt_replay_server and $opt_replay_server_manual are declared earlier in the
+# file for the END block. See the "Forward declarations" comment near the top.
 
 my $config; # The currently running config
 my $current_config_name; # The currently running config file template
@@ -443,7 +443,21 @@ sub main {
     mysql_install_db(default_mysqld(), "$opt_vardir/install.db");
     make_readonly("$opt_vardir/install.db");
     
-    # Start replay server if --replay-server option is specified
+    # Start replay server if --replay-server option is specified.
+    # Refuse if --parallel > 1 was explicitly requested; the replay server is
+    # a single shared instance and cannot serve multiple concurrent workers.
+    # (The "auto" case is resolved later and re-checked below.)
+    if ( $opt_replay_server || $opt_replay_server_manual )
+    {
+      if ($opt_parallel ne "auto" && $opt_parallel > 1)
+      {
+        mtr_error("--replay-server / --replay-server-manual cannot be used " .
+                  "together with --parallel > 1 (parallel=$opt_parallel). " .
+                  "The replay server is a single shared instance and cannot " .
+                  "serve multiple concurrent workers. " .
+                  "Re-run with --parallel=1.");
+      }
+    }
     if ( $opt_replay_server )
     {
       start_replay_server();
@@ -496,6 +510,14 @@ sub main {
     $opt_parallel= 1;
   }
 
+  if ($opt_parallel > 1 && ($opt_replay_server || $opt_replay_server_manual)) {
+    mtr_error("--replay-server and --replay-server-manual cannot be used " .
+              "together with --parallel > 1 (parallel=$opt_parallel). " .
+              "The replay server is a single shared instance and cannot " .
+              "serve multiple concurrent workers. " .
+              "Re-run with --parallel=1.");
+  }
+
   # Create server socket on any free port
   my $server = new IO::Socket::INET
     (

From 85441719a32750e3eb4bb510dd55a4eaccc069e9 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Wed, 22 Apr 2026 15:54:59 +0300
Subject: [PATCH 15/50] MDEV-39368: Make mysql-test-run check if replay server
 is alive

and restart it if needed.
---
 mysql-test/mariadb-test-run.pl | 181 +++++++++++++++++++++++++++++++--
 1 file changed, 174 insertions(+), 7 deletions(-)

diff --git a/mysql-test/mariadb-test-run.pl b/mysql-test/mariadb-test-run.pl
index dbdc7f9b42756..adf9f7f0ed476 100755
--- a/mysql-test/mariadb-test-run.pl
+++ b/mysql-test/mariadb-test-run.pl
@@ -3095,6 +3095,165 @@ sub _install_replay_server_signal_handlers {
 }
 
 
+#
+# Shared PID file so worker-process restarts of the replay server are visible
+# to the parent's stop logic (END block).
+#
+sub _replay_pid_file {
+  return "$opt_vardir/tmp/replay_server.current_pid";
+}
+
+sub _write_replay_pid_file {
+  my ($pid) = @_;
+  return unless defined $pid;
+  my $path = _replay_pid_file();
+  if (open my $fh, '>', $path) {
+    print $fh "$pid\n";
+    close $fh;
+  } else {
+    mtr_warning("Could not write replay pid file $path: $!");
+  }
+}
+
+sub _read_replay_pid_file {
+  my $path = _replay_pid_file();
+  return undef unless -f $path;
+  open my $fh, '<', $path or return undef;
+  my $pid = <$fh>;
+  close $fh;
+  return undef unless defined $pid;
+  chomp $pid;
+  return ($pid =~ /^\d+$/) ? $pid : undef;
+}
+
+#
+# Ping the replay server with SELECT '<test_name>' AS next_testcase, enforcing
+# a 5-second timeout. Returns 1 on success, 0 on failure/timeout.
+#
+sub _ping_replay_server {
+  my ($test_name) = @_;
+  my $sock = $ENV{REPLAY_SERVER_SOCKET};
+  return 0 unless $sock && -S $sock;
+
+  my $mysql_exe = mtr_exe_maybe_exists("$path_client_bindir/mariadb");
+  return 0 unless $mysql_exe && -x $mysql_exe;
+
+  # Escape single quotes in test name for SQL.
+  my $escaped = $test_name;
+  $escaped =~ s/'/''/g;
+  my $sql = "SELECT '$escaped' AS next_testcase";
+
+  my $pid = fork();
+  if (!defined $pid) {
+    mtr_warning("fork() failed in _ping_replay_server: $!");
+    return 0;
+  }
+  if ($pid == 0) {
+    # Child: run the client, redirect output to /dev/null, exec.
+    open(STDIN,  '<', '/dev/null');
+    open(STDOUT, '>', '/dev/null');
+    open(STDERR, '>', '/dev/null');
+    exec($mysql_exe,
+         "--no-defaults",
+         "--protocol=socket",
+         "--socket=$sock",
+         "--user=root",
+         "--connect-timeout=3",
+         "-N", "-B",
+         "-e", $sql);
+    POSIX::_exit(127);
+  }
+
+  # Parent: wait up to 5 seconds.
+  my $status;
+  my $timed_out = 0;
+  eval {
+    local $SIG{ALRM} = sub { die "timeout\n" };
+    alarm(5);
+    waitpid($pid, 0);
+    $status = $?;
+    alarm(0);
+  };
+  if ($@) {
+    # Timeout.
+    alarm(0);
+    $timed_out = 1;
+    kill 'KILL', $pid;
+    waitpid($pid, 0);
+  }
+  return 0 if $timed_out;
+  return ($status == 0) ? 1 : 0;
+}
+
+#
+# Before each test, verify that the replay server is alive and responsive.
+# If not, kill the stale process (if any) and restart the server (for
+# --replay-server) or wait for the user to restart it (--replay-server-manual).
+#
+sub check_replay_server {
+  my ($test_name) = @_;
+  return unless ($opt_replay_server || $opt_replay_server_manual);
+  return unless $ENV{REPLAY_SERVER_SOCKET};
+
+  return if _ping_replay_server($test_name);
+
+  print STDERR "mysql-test-run: *** WARNING: Replay server unresponsive " .
+               "before test '$test_name'\n";
+
+  # Kill any stale process from the old PID.
+  my $old_pid = _read_replay_pid_file() // $ENV{REPLAY_SERVER_PID};
+  if (defined $old_pid && $old_pid =~ /^\d+$/ && kill(0, $old_pid)) {
+    print STDERR "mysql-test-run: killing stale replay server (pid $old_pid)\n";
+    kill 'TERM', $old_pid;
+    my $waited = 0;
+    while ($waited < 5 && kill(0, $old_pid)) {
+      sleep 1;
+      $waited++;
+    }
+    if (kill 0, $old_pid) {
+      kill 'KILL', $old_pid;
+      sleep 1;
+    }
+  }
+
+  # Remove stale socket / pid / info so restart can succeed.
+  my $dir = "$opt_vardir/extra_server_1";
+  unlink "$dir/mysqld.sock" if -e "$dir/mysqld.sock";
+  unlink "$dir/mysqld.pid"  if -e "$dir/mysqld.pid";
+  unlink "$opt_vardir/tmp/extra_server_1.info"
+    if -f "$opt_vardir/tmp/extra_server_1.info";
+
+  if ($opt_replay_server) {
+    print STDERR "mysql-test-run: restarting replay server...\n";
+    start_replay_server();
+    _write_replay_pid_file($ENV{REPLAY_SERVER_PID});
+    print STDERR "mysql-test-run: replay server restarted (pid " .
+                 ($ENV{REPLAY_SERVER_PID} // "?") . ")\n";
+  } else {
+    # --replay-server-manual: can't auto-restart. Wait for the user.
+    print STDERR "mysql-test-run: --replay-server-manual is set; " .
+                 "waiting for you to restart the replay server on socket " .
+                 "$ENV{REPLAY_SERVER_SOCKET} ...\n";
+    while (!_ping_replay_server($test_name)) {
+      sleep 2;
+    }
+    # Try to refresh the PID from the pid file written by the user's server.
+    my $pid_file = "$opt_vardir/extra_server_1/mysqld.pid";
+    if (-f $pid_file && open my $fh, '<', $pid_file) {
+      my $new_pid = <$fh>;
+      close $fh;
+      chomp $new_pid if defined $new_pid;
+      if (defined $new_pid && $new_pid =~ /^\d+$/) {
+        $ENV{REPLAY_SERVER_PID} = $new_pid;
+        _write_replay_pid_file($new_pid);
+      }
+    }
+    print STDERR "mysql-test-run: replay server is responsive again, " .
+                 "continuing with test '$test_name'\n";
+  }
+}
+
+
 sub start_replay_server {
   mtr_report("Starting replay server...");
   $replay_server_parent_pid = $$;
@@ -3145,7 +3304,8 @@ sub start_replay_server {
   # Store for cleanup and export to environment
   $ENV{REPLAY_SERVER_SOCKET} = $info{SOCKET};
   $ENV{REPLAY_SERVER_PID} = $info{PID};
-  
+  _write_replay_pid_file($info{PID});
+
   mtr_report("Replay server started on socket: $info{SOCKET}");
 }
 
@@ -3295,7 +3455,8 @@ sub start_replay_server_manual {
   # Store for cleanup and export to environment
   $ENV{REPLAY_SERVER_SOCKET} = $socket;
   $ENV{REPLAY_SERVER_PID} = $pid;
-  
+  _write_replay_pid_file($pid);
+
   mtr_report("Replay server detected with PID: $pid");
   mtr_report("Socket: $socket");
   mtr_report("Replay server is ready!");
@@ -3304,12 +3465,13 @@ sub start_replay_server_manual {
 
 sub stop_replay_server {
   return unless ($opt_replay_server || $opt_replay_server_manual);
-  return unless $ENV{REPLAY_SERVER_PID};
-  
+  # Prefer the PID from the shared file (it may be fresher than our env var
+  # if a worker restarted the server).
+  my $pid = _read_replay_pid_file() // $ENV{REPLAY_SERVER_PID};
+  return unless $pid;
+
   mtr_report("Stopping replay server...");
   
-  my $pid = $ENV{REPLAY_SERVER_PID};
-  
   # Send SIGTERM. The replay server is NOT a direct child of this process
   # (start_extra_server.pl is an intermediate), so waitpid() cannot be used
   # to poll its exit status. Use `kill 0, $pid` (signal 0 - existence check)
@@ -3337,9 +3499,11 @@ sub stop_replay_server {
     }
   }
   
-  # Cleanup info file
+  # Cleanup info file and shared pid file
   my $info_file = "$opt_vardir/tmp/extra_server_1.info";
   unlink $info_file if -f $info_file;
+  my $pid_file = _replay_pid_file();
+  unlink $pid_file if -f $pid_file;
 
   # Mark as stopped so subsequent calls (e.g. from END block) are no-ops
   delete $ENV{REPLAY_SERVER_PID};
@@ -4159,6 +4323,9 @@ ($$)
   $ENV{'MTR_TEST_NAME'} = $tinfo->{name};
   resfile_report_test($tinfo) if $opt_resfile;
 
+  # Verify the replay server is alive before running the test.
+  check_replay_server($tinfo->{name});
+
   for my $key (grep { /^MTR_COMBINATION/ } keys %ENV)
   {
     delete $ENV{$key};

From b38ebeda67016ea3a61373c2e5ba360a35a031bd Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Thu, 23 Apr 2026 12:59:57 +0300
Subject: [PATCH 16/50] MDEV-39368: Fix wrong behavior for empty Replay Context

If the previous command was EXPLAIN, it would use its context.
If the previous command was not an EXPLAIN, nothing would be printed.
---
 client/mysqltest.cc                       | 104 +++++++++++++++++++---
 mysql-test/main/replay_server_test.result |   5 ++
 mysql-test/main/replay_server_test.test   |   2 +
 mysql-test/mariadb-test-run.pl            |   4 +-
 4 files changed, 102 insertions(+), 13 deletions(-)

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index a668bbb2fd7b9..5728bca167158 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -8664,6 +8664,78 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
   DBUG_VOID_RETURN;
 }
 
+
+/*
+  Run an EXPLAIN query directly on the replay server (no context replay),
+  appending its output (headings + rows + warnings) to ds.
+
+  This is the fallback used when the test server produced an empty
+  optimizer_context for an EXPLAIN query.
+*/
+static void run_explain_directly_on_replay(const char *query, size_t query_len,
+                                           DYNAMIC_STRING *ds)
+{
+  DBUG_ENTER("run_explain_directly_on_replay");
+
+  if (ensure_replay_server_connection() != 0)
+  {
+    fprintf(stdout, "ReplayTest: Failed to connect to replay server\n");
+    DBUG_VOID_RETURN;
+  }
+
+  if (mysql_real_query(replay_server_mysql, query, (ulong)query_len))
+  {
+    fprintf(stdout,
+            "ReplayTest: Direct EXPLAIN failed on replay server: %d %s\n",
+            mysql_errno(replay_server_mysql),
+            mysql_error(replay_server_mysql));
+    fprintf(stdout, "ReplayTest: Failed query was: %.*s\n",
+            (int)query_len, query);
+    DBUG_VOID_RETURN;
+  }
+
+  do
+  {
+    MYSQL_RES *res= mysql_store_result(replay_server_mysql);
+    if (res)
+    {
+      MYSQL_FIELD *fields= mysql_fetch_fields(res);
+      uint num_fields= mysql_num_fields(res);
+      MYSQL_ROW row;
+
+      if (!display_result_vertically)
+        append_table_headings(ds, fields, num_fields);
+
+      while ((row= mysql_fetch_row(res)))
+      {
+        uint i;
+        ulong *lengths= mysql_fetch_lengths(res);
+        for (i= 0; i < num_fields; i++)
+          append_field(ds, i, &fields[i], row[i], lengths[i], !row[i]);
+        if (!display_result_vertically)
+          dynstr_append_mem(ds, "\n", 1);
+      }
+      mysql_free_result(res);
+    }
+  } while (mysql_next_result(replay_server_mysql) == 0);
+
+  /* Append warnings from the EXPLAIN query */
+  if (!disable_warnings)
+  {
+    DYNAMIC_STRING ds_warn;
+    init_dynamic_string(&ds_warn, "", 256, 256);
+    if (append_warnings(&ds_warn, replay_server_mysql) || ds_warn.length)
+    {
+      dynstr_append_mem(ds, "Warnings:\n", 10);
+      dynstr_append_mem(ds, ds_warn.str, ds_warn.length);
+    }
+    dynstr_free(&ds_warn);
+  }
+
+  DBUG_VOID_RETURN;
+}
+
+
 /*
   Run query using MySQL C API
 
@@ -8727,7 +8799,11 @@ void run_query_normal(struct st_connection *cn, struct st_command *command,
   {
     replay_mode_active= TRUE;
     verbose_msg("ReplayTest: Detected EXPLAIN FORMAT=JSON query, activating replay mode");
-    
+
+    /* Clear any previously-recorded context left over from an earlier query
+       (e.g. a prior EXPLAIN whose context must not leak into this one). */
+    (void) mysql_real_query(mysql, "SET optimizer_record_context=0", 30);
+
     /* Step 1: Set optimizer_record_context=1 */
     if (mysql_real_query(mysql, "SET optimizer_record_context=1", 30))
     {
@@ -8820,13 +8896,15 @@ void run_query_normal(struct st_connection *cn, struct st_command *command,
 	  else
 	  {
 	    MYSQL_RES *context_res= mysql_store_result(mysql);
+	    my_bool have_context= FALSE;
 	    if (context_res && mysql_num_rows(context_res) > 0)
 	    {
 	      MYSQL_ROW context_row= mysql_fetch_row(context_res);
 	      if (context_row && context_row[0])
 	      {
 	        const char *sql_script= context_row[0];
-	        
+	        have_context= TRUE;
+
 	        /* Step 3: Connect to replay server and execute queries */
 	        if (ensure_replay_server_connection() == 0)
 	        {
@@ -8837,18 +8915,22 @@ void run_query_normal(struct st_connection *cn, struct st_command *command,
 	          fprintf(stdout, "ReplayTest: Failed to connect to replay server\n");
 	        }
 	      }
-	      else
-	      {
-	        fprintf(stdout, "ReplayTest: optimizer_context returned NULL\n");
-	      }
-	      mysql_free_result(context_res);
 	    }
-	    else
+	    if (context_res)
+	      mysql_free_result(context_res);
+
+	    if (!have_context)
 	    {
-	      fprintf(stdout, "ReplayTest: optimizer_context returned no rows\n");
-	      if (context_res)
-	        mysql_free_result(context_res);
+	      /* Empty context: fall back to running the EXPLAIN directly on the
+	         replay server. */
+	      verbose_msg("ReplayTest: empty optimizer_context, running EXPLAIN "
+	                  "directly on replay server");
+	      run_explain_directly_on_replay(query, query_len, ds);
 	    }
+
+	    /* Clear the test server's recorded context so it doesn't leak into
+	       the next EXPLAIN. */
+	    (void) mysql_real_query(mysql, "SET optimizer_record_context=0", 30);
 	  }
 	  
 	  replay_mode_active= FALSE;
diff --git a/mysql-test/main/replay_server_test.result b/mysql-test/main/replay_server_test.result
index f28194679d07c..656f043542d4d 100644
--- a/mysql-test/main/replay_server_test.result
+++ b/mysql-test/main/replay_server_test.result
@@ -75,4 +75,9 @@ explain
 SELECT * FROM t1 WHERE b < 22;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+explain extended select LENGTH(CONCAT('aa','bbb'));
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+Warnings:
+Note	1003	select octet_length(concat('aa','bbb')) AS `LENGTH(CONCAT('aa','bbb'))`
 DROP TABLE t1;
diff --git a/mysql-test/main/replay_server_test.test b/mysql-test/main/replay_server_test.test
index 178fac64e3613..750c41aeebc71 100644
--- a/mysql-test/main/replay_server_test.test
+++ b/mysql-test/main/replay_server_test.test
@@ -60,4 +60,6 @@ SELECT * FROM t1 WHERE a < 22;
 explain
 SELECT * FROM t1 WHERE b < 22;
 
+explain extended select LENGTH(CONCAT('aa','bbb'));
+
 DROP TABLE t1;
diff --git a/mysql-test/mariadb-test-run.pl b/mysql-test/mariadb-test-run.pl
index adf9f7f0ed476..54835ca294324 100755
--- a/mysql-test/mariadb-test-run.pl
+++ b/mysql-test/mariadb-test-run.pl
@@ -3160,8 +3160,8 @@ sub _ping_replay_server {
          "--user=root",
          "--connect-timeout=3",
          "-N", "-B",
-         "-e", $sql);
-    POSIX::_exit(127);
+         "-e", $sql)
+      or POSIX::_exit(127);
   }
 
   # Parent: wait up to 5 seconds.

From 2b6a91f19d95e43d80ee387ab39e64ab845f2622 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Thu, 23 Apr 2026 13:48:09 +0300
Subject: [PATCH 17/50] MDEV-39368: When replay query fails, print the original
 query location in test file

---
 client/mysqltest.cc | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index 5728bca167158..048de6a0902ce 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -8437,6 +8437,34 @@ static void log_replay_query(const char *query, size_t query_len)
   }
 }
 
+/*
+  Print the current test-file location (file, line, and include stack) to the
+  given stream. Mirrors the format used by make_error_message() for regular
+  mysqltest errors, but prefixed with "ReplayTest: " to group with surrounding
+  replay diagnostics.
+*/
+static void print_replay_test_location(FILE *f)
+{
+  if (cur_file && cur_file != file_stack)
+  {
+    /* Enough for the full 16-entry include stack. */
+    char buf[4096];
+    buf[0]= '\0';
+    fprintf(f, "ReplayTest: In included file \"%s\":\n",
+            cur_file->file_name);
+    print_file_stack(buf, buf + sizeof(buf));
+    if (buf[0])
+      fprintf(f, "ReplayTest: %s", buf);
+  }
+  else if (cur_file && cur_file->file_name)
+  {
+    fprintf(f, "ReplayTest: In file \"%s\"\n", cur_file->file_name);
+  }
+  if (start_lineno > 0)
+    fprintf(f, "ReplayTest: At line %u\n", start_lineno);
+}
+
+
 /*
   Execute queries from SQL script on replay server
   Split by ";\n" and execute each query
@@ -8488,6 +8516,7 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
                   mysql_errno(replay_server_mysql),
                   mysql_error(replay_server_mysql));
           fprintf(stdout, "ReplayTest: Failed query was: %.*s\n", (int)query_len, query_start);
+          print_replay_test_location(stdout);
           goto cleanup;
         }
         
@@ -8580,6 +8609,7 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
                 mysql_errno(replay_server_mysql),
                 mysql_error(replay_server_mysql));
         fprintf(stdout, "ReplayTest: Failed query was: %.*s\n", (int)query_len, query_start);
+        print_replay_test_location(stdout);
         goto cleanup;
       }
       

From e509e11e5c4836df292bc6c5caedb86fbd4de85a Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Thu, 23 Apr 2026 13:52:21 +0300
Subject: [PATCH 18/50] MDEV-39368: When replay query fails, print "*** REPLAY
 FAILED ***" instead of EXPLAIN output.

---
 client/mysqltest.cc | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index 048de6a0902ce..07f6fbf1db27c 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -8517,6 +8517,13 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
                   mysql_error(replay_server_mysql));
           fprintf(stdout, "ReplayTest: Failed query was: %.*s\n", (int)query_len, query_start);
           print_replay_test_location(stdout);
+          
+          /* If this was an EXPLAIN query, add failure marker to result output */
+          if (is_explain)
+          {
+            dynstr_append_mem(&result, "*** REPLAY FAILED ***\n", 22);
+          }
+          
           goto cleanup;
         }
         

From fca1fd673b8fc3e0bc28f32bdb40b5b209a7aa7b Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Thu, 23 Apr 2026 22:42:47 +0300
Subject: [PATCH 19/50] MDEV-39368: Disable main/extra_server_example.test

It seems to get mtr into a state where the replay server is unusable.
---
 ...tra_server_example.test => extra_server_example.test.DISABLED} | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 rename mysql-test/main/{extra_server_example.test => extra_server_example.test.DISABLED} (100%)

diff --git a/mysql-test/main/extra_server_example.test b/mysql-test/main/extra_server_example.test.DISABLED
similarity index 100%
rename from mysql-test/main/extra_server_example.test
rename to mysql-test/main/extra_server_example.test.DISABLED

From 21dc11859ce2727bc78eda435fbdf0e91f7f44f4 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Thu, 23 Apr 2026 22:40:31 +0300
Subject: [PATCH 20/50] MDEV-39368: Improve error reporting.

A whole class of errors were not printed to the test output.
---
 client/mysqltest.cc | 40 +++++++++++++++++++++++++++-------------
 1 file changed, 27 insertions(+), 13 deletions(-)

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index 07f6fbf1db27c..762c57c0d74ae 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -8512,21 +8512,22 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
         /* Execute the query */
         if (mysql_real_query(replay_server_mysql, query_start, query_len))
         {
-          fprintf(stdout, "ReplayTest: Query failed on replay server: %d %s\n",
-                  mysql_errno(replay_server_mysql),
-                  mysql_error(replay_server_mysql));
-          fprintf(stdout, "ReplayTest: Failed query was: %.*s\n", (int)query_len, query_start);
+          char buf[512];
+          int len= my_snprintf(buf, sizeof(buf),
+                               "ReplayTest: Query error: %s\n",
+                               mysql_error(replay_server_mysql));
+          fputs(buf, stdout);
           print_replay_test_location(stdout);
-          
+
           /* If this was an EXPLAIN query, add failure marker to result output */
           if (is_explain)
           {
-            dynstr_append_mem(&result, "*** REPLAY FAILED ***\n", 22);
+            dynstr_append_mem(&result, buf, len);
           }
-          
+
           goto cleanup;
         }
-        
+
         /* Process results */
         do
         {
@@ -8558,6 +8559,16 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
             }
             mysql_free_result(res);
           }
+          if (mysql_errno(replay_server_mysql))
+          {
+            char buf[512];
+            int len= my_snprintf(buf, sizeof(buf),
+                                 "ReplayTest: Query error: %s\n",
+                                 mysql_error(replay_server_mysql));
+            fputs(buf, stdout);
+            if (is_explain)
+              dynstr_append_mem(&result, buf, len);
+          }
         } while (mysql_next_result(replay_server_mysql) == 0);
 
         /* Collect warnings from the EXPLAIN query (replay server) */
@@ -8577,7 +8588,7 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
         if (is_explain)
         {
           found_explain= TRUE;
-          verbose_msg("ReplayTest: Found EXPLAIN FORMAT=JSON, stopping script execution");
+          verbose_msg("ReplayTest: Found EXPLAIN, stopping script execution");
           break;
         }
       }
@@ -8722,12 +8733,15 @@ static void run_explain_directly_on_replay(const char *query, size_t query_len,
 
   if (mysql_real_query(replay_server_mysql, query, (ulong)query_len))
   {
-    fprintf(stdout,
-            "ReplayTest: Direct EXPLAIN failed on replay server: %d %s\n",
-            mysql_errno(replay_server_mysql),
-            mysql_error(replay_server_mysql));
+    char buf[512];
+    int len= my_snprintf(buf, sizeof(buf),
+                         "ReplayTest: Direct EXPLAIN failed on replay server: %d %s\n",
+                         mysql_errno(replay_server_mysql),
+                         mysql_error(replay_server_mysql));
+    fputs(buf, stdout);
     fprintf(stdout, "ReplayTest: Failed query was: %.*s\n",
             (int)query_len, query);
+    dynstr_append_mem(ds, buf, len);
     DBUG_VOID_RETURN;
   }
 

From ae788761a1da53410ba3ac968050b6ef44776421 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 24 Apr 2026 12:42:09 +0300
Subject: [PATCH 21/50] MDEV-39368: Add disable_replay command, first variant.

Usage:
--disable_replay next_query <arbitrary reason text>

If the next query after this is an EXPLAIN, its processing will be disabled.
---
 client/mysqltest.cc | 122 +++++++++++++++++++++++++++++++++++++-------
 1 file changed, 103 insertions(+), 19 deletions(-)

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index 762c57c0d74ae..00656df0a7b95 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -277,6 +277,8 @@ static const char *replay_server_socket= NULL;
 static my_bool replay_test_mode= FALSE;
 static FILE *replay_log_file= NULL;
 static const char *replay_log_path= NULL;
+static my_bool disable_replay_next_query= FALSE;
+static char disable_replay_reason[512]= {0};
 
 /* Precompiled re's */
 static regex_t ps_re;     /* the query can be run using PS protocol */
@@ -430,6 +432,7 @@ enum enum_commands {
   Q_PS_BIND,
   Q_PS_EXECUTE,
   Q_PS_CLOSE,
+  Q_DISABLE_REPLAY,
   Q_UNKNOWN,			       /* Unknown command.   */
   Q_COMMENT,			       /* Comments, ignored. */
   Q_COMMENT_WITH_COMMAND,
@@ -555,6 +558,7 @@ const char *command_names[]=
   "PS_bind",
   "PS_execute",
   "PS_close",
+  "disable_replay",
   0
 };
 
@@ -8465,6 +8469,68 @@ static void print_replay_test_location(FILE *f)
 }
 
 
+/*
+  Handle "disable_replay next_query <reason>" command.
+
+  Syntax:
+    disable_replay next_query <arbitrary reason text>
+
+  The first token after the command must be the literal word "next_query".
+  Everything after "next_query" is the reason string (spaces allowed).
+  Sets a one-shot flag consumed by the next SQL query executed via
+  run_query_normal(); if that query is EXPLAIN, replay-server processing is
+  skipped and the EXPLAIN runs normally against the test server.
+
+  Any syntax violation is a hard error (die).
+*/
+static void do_disable_replay(struct st_command *command)
+{
+  const char *p= command->first_argument;
+  const char *end= command->end;
+  const char *tok;
+  size_t tok_len;
+  size_t reason_len;
+  DBUG_ENTER("do_disable_replay");
+
+  /* Skip leading whitespace */
+  while (p < end && my_isspace(charset_info, *p))
+    p++;
+
+  tok= p;
+  while (p < end && !my_isspace(charset_info, *p))
+    p++;
+  tok_len= (size_t)(p - tok);
+
+  if (tok_len != 10 || strncmp(tok, "next_query", 10) != 0)
+    die("Syntax: disable_replay next_query <reason>");
+
+  /* Skip whitespace between "next_query" and the reason */
+  while (p < end && my_isspace(charset_info, *p))
+    p++;
+
+  if (p >= end)
+    die("Syntax: disable_replay next_query <reason>  (reason missing)");
+
+  /* Copy reason, trim trailing whitespace */
+  reason_len= (size_t)(end - p);
+  while (reason_len > 0 &&
+         my_isspace(charset_info, p[reason_len - 1]))
+    reason_len--;
+
+  if (reason_len >= sizeof(disable_replay_reason))
+    reason_len= sizeof(disable_replay_reason) - 1;
+  memcpy(disable_replay_reason, p, reason_len);
+  disable_replay_reason[reason_len]= '\0';
+
+  disable_replay_next_query= TRUE;
+  command->last_argument= command->end;
+
+  verbose_msg("disable_replay: next query will bypass replay server (reason: %s)",
+              disable_replay_reason);
+  DBUG_VOID_RETURN;
+}
+
+
 /*
   Execute queries from SQL script on replay server
   Split by ";\n" and execute each query
@@ -8844,29 +8910,44 @@ void run_query_normal(struct st_connection *cn, struct st_command *command,
     break;
   }
 
-  /* ReplayTest mode: Set optimizer_record_context BEFORE sending EXPLAIN query */
-  if (replay_test_mode && (flags & QUERY_SEND_FLAG) && (flags & QUERY_REAP_FLAG) &&
-      is_explain_query(query, query_len))
+  /* Consume the one-shot "disable_replay next_query" flag: it applies to
+     exactly one SQL query executed via this function, whether or not it is
+     an EXPLAIN. */
   {
-    replay_mode_active= TRUE;
-    verbose_msg("ReplayTest: Detected EXPLAIN FORMAT=JSON query, activating replay mode");
-
-    /* Clear any previously-recorded context left over from an earlier query
-       (e.g. a prior EXPLAIN whose context must not leak into this one). */
-    (void) mysql_real_query(mysql, "SET optimizer_record_context=0", 30);
-
-    /* Step 1: Set optimizer_record_context=1 */
-    if (mysql_real_query(mysql, "SET optimizer_record_context=1", 30))
+    my_bool skip_replay_this_query= disable_replay_next_query;
+    if (disable_replay_next_query)
     {
-      fprintf(stdout, "ReplayTest: Failed to set optimizer_record_context: %d %s\n",
-              mysql_errno(mysql), mysql_error(mysql));
-      replay_mode_active= FALSE;
+      verbose_msg("ReplayTest: replay disabled for this query (reason: %s)",
+                  disable_replay_reason);
+      disable_replay_next_query= FALSE;
+      disable_replay_reason[0]= '\0';
     }
-    else
+
+    /* ReplayTest mode: Set optimizer_record_context BEFORE sending EXPLAIN query */
+    if (replay_test_mode && !skip_replay_this_query &&
+        (flags & QUERY_SEND_FLAG) && (flags & QUERY_REAP_FLAG) &&
+        is_explain_query(query, query_len))
     {
-      MYSQL_RES *tmp_res= mysql_store_result(mysql);
-      if (tmp_res)
-        mysql_free_result(tmp_res);
+      replay_mode_active= TRUE;
+      verbose_msg("ReplayTest: Detected EXPLAIN FORMAT=JSON query, activating replay mode");
+
+      /* Clear any previously-recorded context left over from an earlier query
+         (e.g. a prior EXPLAIN whose context must not leak into this one). */
+      (void) mysql_real_query(mysql, "SET optimizer_record_context=0", 30);
+
+      /* Step 1: Set optimizer_record_context=1 */
+      if (mysql_real_query(mysql, "SET optimizer_record_context=1", 30))
+      {
+        fprintf(stdout, "ReplayTest: Failed to set optimizer_record_context: %d %s\n",
+                mysql_errno(mysql), mysql_error(mysql));
+        replay_mode_active= FALSE;
+      }
+      else
+      {
+        MYSQL_RES *tmp_res= mysql_store_result(mysql);
+        if (tmp_res)
+          mysql_free_result(tmp_res);
+      }
     }
   }
 
@@ -11282,6 +11363,9 @@ int main(int argc, char **argv)
       case Q_OPTIMIZER_TRACE:
         enable_optimizer_trace(cur_con);
         break;
+      case Q_DISABLE_REPLAY:
+        do_disable_replay(command);
+        break;
       case Q_SEND_SHUTDOWN:
         handle_command_error(command,
                              mysql_shutdown(cur_con->mysql,

From 5014edeb42a8634934269e3c0d1c040606def7f0 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 24 Apr 2026 13:23:46 +0300
Subject: [PATCH 22/50] MDEV-39368: Add "--disable_replay testfile reason"
 support.

Disable replay use for the whole file.
---
 client/mysqltest.cc | 70 +++++++++++++++++++++++++++++++++------------
 1 file changed, 52 insertions(+), 18 deletions(-)

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index 00656df0a7b95..b6e4406b36647 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -279,6 +279,8 @@ static FILE *replay_log_file= NULL;
 static const char *replay_log_path= NULL;
 static my_bool disable_replay_next_query= FALSE;
 static char disable_replay_reason[512]= {0};
+static my_bool disable_replay_testfile= FALSE;
+static char disable_replay_testfile_reason[512]= {0};
 
 /* Precompiled re's */
 static regex_t ps_re;     /* the query can be run using PS protocol */
@@ -8470,16 +8472,20 @@ static void print_replay_test_location(FILE *f)
 
 
 /*
-  Handle "disable_replay next_query <reason>" command.
+  Handle "disable_replay <scope> <reason>" command.
 
   Syntax:
     disable_replay next_query <arbitrary reason text>
+    disable_replay testfile   <arbitrary reason text>
 
-  The first token after the command must be the literal word "next_query".
-  Everything after "next_query" is the reason string (spaces allowed).
-  Sets a one-shot flag consumed by the next SQL query executed via
-  run_query_normal(); if that query is EXPLAIN, replay-server processing is
-  skipped and the EXPLAIN runs normally against the test server.
+  The first token after the command must be "next_query" or "testfile".
+  Everything after the scope token is the reason string (spaces allowed).
+
+  - "next_query": one-shot; the next SQL query executed via run_query_normal()
+    bypasses replay-server processing (if it is EXPLAIN). The flag is consumed
+    by that one query regardless of whether it is EXPLAIN.
+  - "testfile": sticky; disables replay-server processing for every EXPLAIN
+    until mysqltest exits.
 
   Any syntax violation is a hard error (die).
 */
@@ -8490,6 +8496,9 @@ static void do_disable_replay(struct st_command *command)
   const char *tok;
   size_t tok_len;
   size_t reason_len;
+  my_bool is_testfile;
+  char *reason_buf;
+  size_t reason_buf_size;
   DBUG_ENTER("do_disable_replay");
 
   /* Skip leading whitespace */
@@ -8501,15 +8510,30 @@ static void do_disable_replay(struct st_command *command)
     p++;
   tok_len= (size_t)(p - tok);
 
-  if (tok_len != 10 || strncmp(tok, "next_query", 10) != 0)
-    die("Syntax: disable_replay next_query <reason>");
+  if (tok_len == 10 && strncmp(tok, "next_query", 10) == 0)
+    is_testfile= FALSE;
+  else if (tok_len == 8 && strncmp(tok, "testfile", 8) == 0)
+    is_testfile= TRUE;
+  else
+    die("Syntax: disable_replay next_query|testfile <reason>");
 
-  /* Skip whitespace between "next_query" and the reason */
+  /* Skip whitespace between the scope token and the reason */
   while (p < end && my_isspace(charset_info, *p))
     p++;
 
   if (p >= end)
-    die("Syntax: disable_replay next_query <reason>  (reason missing)");
+    die("Syntax: disable_replay next_query|testfile <reason>  (reason missing)");
+
+  if (is_testfile)
+  {
+    reason_buf= disable_replay_testfile_reason;
+    reason_buf_size= sizeof(disable_replay_testfile_reason);
+  }
+  else
+  {
+    reason_buf= disable_replay_reason;
+    reason_buf_size= sizeof(disable_replay_reason);
+  }
 
   /* Copy reason, trim trailing whitespace */
   reason_len= (size_t)(end - p);
@@ -8517,16 +8541,25 @@ static void do_disable_replay(struct st_command *command)
          my_isspace(charset_info, p[reason_len - 1]))
     reason_len--;
 
-  if (reason_len >= sizeof(disable_replay_reason))
-    reason_len= sizeof(disable_replay_reason) - 1;
-  memcpy(disable_replay_reason, p, reason_len);
-  disable_replay_reason[reason_len]= '\0';
+  if (reason_len >= reason_buf_size)
+    reason_len= reason_buf_size - 1;
+  memcpy(reason_buf, p, reason_len);
+  reason_buf[reason_len]= '\0';
 
-  disable_replay_next_query= TRUE;
-  command->last_argument= command->end;
+  if (is_testfile)
+  {
+    disable_replay_testfile= TRUE;
+    verbose_msg("disable_replay: replay disabled for the rest of this test "
+                "file (reason: %s)", disable_replay_testfile_reason);
+  }
+  else
+  {
+    disable_replay_next_query= TRUE;
+    verbose_msg("disable_replay: next query will bypass replay server "
+                "(reason: %s)", disable_replay_reason);
+  }
 
-  verbose_msg("disable_replay: next query will bypass replay server (reason: %s)",
-              disable_replay_reason);
+  command->last_argument= command->end;
   DBUG_VOID_RETURN;
 }
 
@@ -8925,6 +8958,7 @@ void run_query_normal(struct st_connection *cn, struct st_command *command,
 
     /* ReplayTest mode: Set optimizer_record_context BEFORE sending EXPLAIN query */
     if (replay_test_mode && !skip_replay_this_query &&
+        !disable_replay_testfile &&
         (flags & QUERY_SEND_FLAG) && (flags & QUERY_REAP_FLAG) &&
         is_explain_query(query, query_len))
     {

From 959bcda6526d562896e2f2025774efe57dcaf860 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 24 Apr 2026 13:36:26 +0300
Subject: [PATCH 23/50] MDEV-39368: Print errors for context preparation
 queries into query output.

I don't think we can print warnings, we would get spurious test failures.
---
 client/mysqltest.cc | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index b6e4406b36647..947219ebb78ad 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -8617,13 +8617,11 @@ static void execute_replay_queries(const char *sql_script, DYNAMIC_STRING *ds)
                                mysql_error(replay_server_mysql));
           fputs(buf, stdout);
           print_replay_test_location(stdout);
+          verbose_msg("%s", buf);
 
-          /* If this was an EXPLAIN query, add failure marker to result output */
-          if (is_explain)
-          {
-            dynstr_append_mem(&result, buf, len);
-          }
-
+          /* Add failure marker to result output */
+          dynstr_append_mem(&result, buf, len);
+          
           goto cleanup;
         }
 

From 418dc35ba1d634b12f15f73fcf13fa2122c52922 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 24 Apr 2026 13:42:28 +0300
Subject: [PATCH 24/50] MDEV-39416: Context Replay for MRG_MyISAM tables: Table
 is read-only error

Disable the testcase with explanation.
---
 mysql-test/suite/merge/merge.test | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mysql-test/suite/merge/merge.test b/mysql-test/suite/merge/merge.test
index 42f510d4d1ac0..e79ac62fde212 100644
--- a/mysql-test/suite/merge/merge.test
+++ b/mysql-test/suite/merge/merge.test
@@ -314,6 +314,7 @@ EXPLAIN SELECT * FROM t2 WHERE fileset_id = 2
 AND file_code BETWEEN '0000000115' AND '0000000120' LIMIT 1;
 EXPLAIN SELECT * FROM t1 WHERE fileset_id = 2
 AND file_code BETWEEN '0000000115' AND '0000000120' LIMIT 1;
+--disable_replay next_query With MRG_MyISAM tables, one needs to know to INSERT into different table.
 EXPLAIN SELECT * FROM t2 WHERE fileset_id = 2
 AND file_code = '0000000115' LIMIT 1;
 DROP TABLE t2, t1;

From cd95c0cab071cc47a595acd87a13c466dfd9c7a2 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 24 Apr 2026 14:21:48 +0300
Subject: [PATCH 25/50] MDEV-39368: Test coverage for "--disable_replay
 next_query"

---
 mysql-test/main/replay_server_test.result |  6 ++++++
 mysql-test/main/replay_server_test.test   | 12 ++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/mysql-test/main/replay_server_test.result b/mysql-test/main/replay_server_test.result
index 656f043542d4d..75b113ee7c708 100644
--- a/mysql-test/main/replay_server_test.result
+++ b/mysql-test/main/replay_server_test.result
@@ -80,4 +80,10 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 Warnings:
 Note	1003	select octet_length(concat('aa','bbb')) AS `LENGTH(CONCAT('aa','bbb'))`
+create function add1(i int) returns int deterministic
+return i+1;
+explain select * from t1 where b< add1(b);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+drop function add1;
 DROP TABLE t1;
diff --git a/mysql-test/main/replay_server_test.test b/mysql-test/main/replay_server_test.test
index 750c41aeebc71..41163cc332940 100644
--- a/mysql-test/main/replay_server_test.test
+++ b/mysql-test/main/replay_server_test.test
@@ -62,4 +62,16 @@ SELECT * FROM t1 WHERE b < 22;
 
 explain extended select LENGTH(CONCAT('aa','bbb'));
 
+#
+# Check if disable replay works
+#
+create function add1(i int) returns int deterministic
+  return i+1;
+
+# The following would give this error:
+#    ReplayTest: Query error: FUNCTION test.add1 does not exist
+--disable_replay next_query Don't support SPs.
+explain select * from t1 where b< add1(b);
+
+drop function add1;
 DROP TABLE t1;

From 6ba9658a07e06f9fd7bda446a6d4cf2609c62bf3 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 24 Apr 2026 14:33:54 +0300
Subject: [PATCH 26/50] Add --disable_replay in custom_aggregates_i_s,
 selectivity_notembedded (part)

---
 mysql-test/main/custom_aggregates_i_s.test   | 1 +
 mysql-test/main/selectivity_notembedded.test | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/mysql-test/main/custom_aggregates_i_s.test b/mysql-test/main/custom_aggregates_i_s.test
index dd5eb50d82ce6..89c5fc39cd342 100644
--- a/mysql-test/main/custom_aggregates_i_s.test
+++ b/mysql-test/main/custom_aggregates_i_s.test
@@ -3,6 +3,7 @@
 
 --source include/default_optimizer_switch.inc
 
+--disable_replay testfile Optimizer Context doesn't include SPs that query uses.
 --disable_ps2_protocol
 
 flush status;
diff --git a/mysql-test/main/selectivity_notembedded.test b/mysql-test/main/selectivity_notembedded.test
index ed2e25b8028fe..8ac0c2a1f421b 100644
--- a/mysql-test/main/selectivity_notembedded.test
+++ b/mysql-test/main/selectivity_notembedded.test
@@ -96,6 +96,7 @@ flush tables;
 
 set @tmp=@@optimizer_trace;
 set optimizer_trace=1;
+--disable_replay next_query Need to preserve optimizer trace
 explain select * from t10  where a in (91303);
 
 #Enable after fix MDEV-32034
@@ -240,6 +241,7 @@ from
 analyze table t1;
 
 set optimizer_trace=1;
+--disable_replay next_query  Need to preserve optimizer trace
 explain select * from t1
 where
   pk in (1,2,3,4,5) and

From 317f0b9ab40adb7d3b8189e56c7a96eb52f023fa Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 24 Apr 2026 15:27:14 +0300
Subject: [PATCH 27/50] MDEV-39368: Make is_explain_query() reject EXPLAIN
 ...FOR CONNECTION,

Also make it use regexes
---
 client/mysqltest.cc | 73 +++++++++++++++++++++++++++++++--------------
 1 file changed, 50 insertions(+), 23 deletions(-)

diff --git a/client/mysqltest.cc b/client/mysqltest.cc
index 947219ebb78ad..c5a11f854d5d7 100644
--- a/client/mysqltest.cc
+++ b/client/mysqltest.cc
@@ -288,6 +288,8 @@ static regex_t ps2_re;    /* the query can be run using PS protocol with second
 static regex_t sp_re;     /* the query can be run as a SP */
 static regex_t view_re;   /* the query can be run as a view*/
 static regex_t cursor_re;    /* the query can be run with cursor protocol*/
+static regex_t explain_re;            /* the query is EXPLAIN (any variant) */
+static regex_t explain_for_conn_re;   /* the query is EXPLAIN ... FOR CONNECTION ... */
 
 static void init_re(void);
 static int match_re(regex_t *, char *);
@@ -8387,36 +8389,39 @@ static int ensure_replay_server_connection()
 }
 
 /*
-  Check if query starts with "EXPLAIN"
-  Returns TRUE if it matches, FALSE otherwise.
-  Returns FALSE for "EXPLAIN FOR ..." (e.g. EXPLAIN FOR CONNECTION), since that
-  form does not trigger query optimization/recording.
+  Check if query is of the form "EXPLAIN ..." that we want to handle via the
+  replay server.
+
+  Returns TRUE if the query starts with the EXPLAIN keyword.
+  Returns FALSE for "EXPLAIN ... FOR CONNECTION ..." forms (e.g.
+  "EXPLAIN FOR CONNECTION <id>" or "EXPLAIN FORMAT=JSON FOR CONNECTION <id>"),
+  since that form does not trigger query optimization/recording.
+
+  Uses the precompiled regexes explain_re / explain_for_conn_re (see init_re).
 */
 static my_bool is_explain_query(const char *query, size_t query_len)
 {
-  const char *p= query;
-  const char *end= query + query_len;
-  
-  while (p < end && my_isspace(charset_info, *p))
-    p++;
-  
-  if (end - p < 7 || strncasecmp(p, "EXPLAIN", 7) != 0)
-    return FALSE;
-  p += 7;
-  
-  if (p >= end || !my_isspace(charset_info, *p))
+  /* match_re / regexec need a null-terminated string; query isn't guaranteed
+     to be null-terminated at query_len. Copy into a temp buffer. */
+  char stack_buf[512];
+  char *buf;
+  my_bool result;
+
+  if (query_len + 1 <= sizeof(stack_buf))
+    buf= stack_buf;
+  else
+    buf= (char*) my_malloc(PSI_NOT_INSTRUMENTED, query_len + 1, MYF(MY_WME));
+  if (!buf)
     return FALSE;
 
-  /* Skip whitespace between EXPLAIN and the next token */
-  while (p < end && my_isspace(charset_info, *p))
-    p++;
+  memcpy(buf, query, query_len);
+  buf[query_len]= '\0';
 
-  /* Reject "EXPLAIN FOR ..." (token "FOR" followed by whitespace or end) */
-  if (end - p >= 3 && strncasecmp(p, "FOR", 3) == 0 &&
-      (end - p == 3 || my_isspace(charset_info, p[3])))
-    return FALSE;
+  result= match_re(&explain_re, buf) && !match_re(&explain_for_conn_re, buf);
 
-  return TRUE;
+  if (buf != stack_buf)
+    my_free(buf);
+  return result;
 }
 
 /*
@@ -10586,11 +10591,31 @@ void init_re(void)
     "^("
     "[[:space:]]*SELECT[[:space:]])";
 
+  /*
+    Filter: query starts with the EXPLAIN keyword.
+  */
+  const char *explain_re_str =
+    "^[[:space:]]*EXPLAIN([[:space:]]|$)";
+
+  /*
+    Filter: EXPLAIN ... FOR CONNECTION ... (any EXPLAIN options between).
+    Matches forms like:
+      EXPLAIN FOR CONNECTION <id>
+      EXPLAIN FORMAT=JSON FOR CONNECTION <id>
+      EXPLAIN EXTENDED FOR CONNECTION <id>
+    The query body of a real EXPLAIN never ends with "FOR CONNECTION", so a
+    plain substring-style match is safe in practice.
+  */
+  const char *explain_for_conn_re_str =
+    "^[[:space:]]*EXPLAIN[[:space:]](.*[[:space:]])?FOR[[:space:]]+CONNECTION([[:space:]]|$)";
+
   init_re_comp(&ps_re, ps_re_str);
   init_re_comp(&ps2_re, ps2_re_str);
   init_re_comp(&sp_re, sp_re_str);
   init_re_comp(&view_re, view_re_str);
   init_re_comp(&cursor_re, cursor_re_str);
+  init_re_comp(&explain_re, explain_re_str);
+  init_re_comp(&explain_for_conn_re, explain_for_conn_re_str);
 }
 
 
@@ -10629,6 +10654,8 @@ void free_re(void)
   regfree(&sp_re);
   regfree(&view_re);
   regfree(&cursor_re);
+  regfree(&explain_re);
+  regfree(&explain_for_conn_re);
 }
 
 /****************************************************************************/

From f2d1f143526fce2c62336ee9f57bd55ee24f1bc7 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 24 Apr 2026 15:33:21 +0300
Subject: [PATCH 28/50] Add --disable_replay next_query in join_outer and
 opt_trace_index_merge_innodb

---
 mysql-test/main/join_outer.test                   | 3 +++
 mysql-test/main/opt_trace_index_merge_innodb.test | 1 +
 2 files changed, 4 insertions(+)

diff --git a/mysql-test/main/join_outer.test b/mysql-test/main/join_outer.test
index 6686d3e939ec9..e6d74e6be6dfe 100644
--- a/mysql-test/main/join_outer.test
+++ b/mysql-test/main/join_outer.test
@@ -1906,6 +1906,7 @@ SELECT t1.x, t2.x, IFNULL(t2.x,0), f(t2.x,0)
                             FROM t t1 LEFT JOIN t t2
                             ON t1.x = t2.x
                             WHERE IFNULL(t2.x,0)=0;
+--disable_replay next_query Don't support SPs.
 explain extended
 SELECT t1.x, t2.x, IFNULL(t2.x,0), f(t2.x,0)
                             FROM t t1 LEFT JOIN t t2
@@ -1915,6 +1916,7 @@ SELECT t1.x, t2.x, IFNULL(t2.x,0), f(t2.x,0)
                             FROM t t1 LEFT JOIN t t2
                             ON t1.x = t2.x
                             WHERE f(t2.x,0)=0;
+--disable_replay next_query Don't support SPs.
 explain extended
 SELECT t1.x, t2.x, IFNULL(t2.x,0), f(t2.x,0)
                             FROM t t1 LEFT JOIN t t2
@@ -1969,6 +1971,7 @@ SELECT t1.col1, t2.col1, t2.col3
 FROM t1 LEFT OUTER JOIN t2 ON t1.col1 = t2.col2
 WHERE f1(t2.col3,0) = 0;
 eval $q2;
+--disable_replay next_query Don't support SPs.
 eval EXPLAIN EXTENDED $q2;
 
 DROP FUNCTION f1;
diff --git a/mysql-test/main/opt_trace_index_merge_innodb.test b/mysql-test/main/opt_trace_index_merge_innodb.test
index 3b8e60f687e39..9d841eb74342d 100644
--- a/mysql-test/main/opt_trace_index_merge_innodb.test
+++ b/mysql-test/main/opt_trace_index_merge_innodb.test
@@ -32,6 +32,7 @@ analyze table t1;
 set optimizer_trace="enabled=on";
 set @tmp_index_merge_ror_cpk=@@optimizer_switch;
 set optimizer_switch='extended_keys=off';
+--disable_replay next_query Need to preserve optimizer trace
 explain select * from t1 where pk1 != 0  and key1 = 1;
 --disable_view_protocol
 select * from information_schema.OPTIMIZER_TRACE;

From 7cafa3bcd8ab3872974189a9e25db1a95002f972 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 24 Apr 2026 15:40:49 +0300
Subject: [PATCH 29/50] More --disable_replay commands.

---
 mysql-test/main/custom_aggregates_i_s.test | 2 +-
 mysql-test/main/derived.test               | 1 +
 mysql-test/main/opt_trace.test             | 2 ++
 mysql-test/main/sp.test                    | 2 ++
 4 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/mysql-test/main/custom_aggregates_i_s.test b/mysql-test/main/custom_aggregates_i_s.test
index 89c5fc39cd342..15577d059f638 100644
--- a/mysql-test/main/custom_aggregates_i_s.test
+++ b/mysql-test/main/custom_aggregates_i_s.test
@@ -3,7 +3,7 @@
 
 --source include/default_optimizer_switch.inc
 
---disable_replay testfile Optimizer Context doesn't include SPs that query uses.
+--disable_replay testfile Don't support SPs.
 --disable_ps2_protocol
 
 flush status;
diff --git a/mysql-test/main/derived.test b/mysql-test/main/derived.test
index c5c27c940c840..cc4a75eab2ee8 100644
--- a/mysql-test/main/derived.test
+++ b/mysql-test/main/derived.test
@@ -1953,6 +1953,7 @@ explain format=json select * from v1 where if( a1 regexp 'def', 'foo', a2 )
 create function f1(a int) returns int DETERMINISTIC return (a+1);
 create view v9 as select * from
   (select c1, f1(c2), sum(c3) from t1 group by c1, f1(c2)) as f (c1, c2, c3);
+--disable_replay next_query Don't support SPs.
 explain format=json select * from v9 where (c3+1) > 10 and c1 > 1 and c2 > 123;
 drop function f1;
 
diff --git a/mysql-test/main/opt_trace.test b/mysql-test/main/opt_trace.test
index 4c8fc52ae2965..6818086e6b468 100644
--- a/mysql-test/main/opt_trace.test
+++ b/mysql-test/main/opt_trace.test
@@ -1,6 +1,8 @@
 --source include/not_embedded.inc
 --source include/have_sequence.inc
 
+--disable_replay testfile Need to preserve optimizer trace
+
 SELECT table_name, column_name FROM information_schema.columns where table_name="OPTIMIZER_TRACE";
 set optimizer_trace="enabled=on";
 show variables like 'optimizer_trace';
diff --git a/mysql-test/main/sp.test b/mysql-test/main/sp.test
index 773f44d5dfa5f..c178ff8b2988d 100644
--- a/mysql-test/main/sp.test
+++ b/mysql-test/main/sp.test
@@ -2,6 +2,8 @@
 --source include/have_partition.inc
 --source include/have_sequence.inc
 
+--disable_replay testfile Don't support SPs. 
+
 #
 # Basic stored PROCEDURE tests
 #

From f6b1adb49a98a401c2e3702a258b0bced187c9f0 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 24 Apr 2026 15:51:17 +0300
Subject: [PATCH 30/50] More --disable_replay commands (2)

---
 mysql-test/main/opt_context_store_ddls.test | 2 ++
 mysql-test/main/status.test                 | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/mysql-test/main/opt_context_store_ddls.test b/mysql-test/main/opt_context_store_ddls.test
index 0e393c8b72d0c..1b1eb351a0194 100644
--- a/mysql-test/main/opt_context_store_ddls.test
+++ b/mysql-test/main/opt_context_store_ddls.test
@@ -3,6 +3,8 @@
 --source include/have_partition.inc
 --source include/no_view_protocol.inc
 
+--disable_replay testfile Don't replay a replay test
+
 set optimizer_record_context=ON;
 show variables like 'optimizer_record_context';
 
diff --git a/mysql-test/main/status.test b/mysql-test/main/status.test
index a3087d9c9c055..912b945e5e5fd 100644
--- a/mysql-test/main/status.test
+++ b/mysql-test/main/status.test
@@ -210,12 +210,14 @@ INSERT INTO t1 VALUES (1), (2);
 SELECT a FROM t1 LIMIT 1;
 SHOW SESSION STATUS LIKE 'Last_query_cost';
 
+--disable_replay next_query Needs to preserve counters
 EXPLAIN SELECT a FROM t1;
 SHOW SESSION STATUS LIKE 'Last_query_cost';
 
 SELECT a FROM t1 UNION SELECT a FROM t1 ORDER BY a;
 SHOW SESSION STATUS LIKE 'Last_query_cost';
 
+--disable_replay next_query Needs to preserve counters
 EXPLAIN SELECT a FROM t1 UNION SELECT a FROM t1 ORDER BY a;
 SHOW SESSION STATUS LIKE 'Last_query_cost';
 

From d6f0035bc7ad2abbc226de594af80adfbfdd3986 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 24 Apr 2026 21:09:22 +0300
Subject: [PATCH 31/50] More --disable_replay commands (3).

---
 mysql-test/main/create.test                           | 1 +
 mysql-test/main/desc_index_range.test                 | 7 +++++++
 mysql-test/main/distinct_notembedded.test             | 1 +
 mysql-test/main/explain_json.test                     | 2 ++
 mysql-test/main/greedy_optimizer.test                 | 2 ++
 mysql-test/main/index_merge_innodb_notembedded.test   | 3 +++
 mysql-test/main/join.test                             | 3 +++
 mysql-test/main/join_cache_cardinality.test           | 2 ++
 mysql-test/main/opt_context_load_stats_basic.test     | 3 +++
 mysql-test/main/opt_context_replay_basic.test         | 2 ++
 mysql-test/main/opt_context_store_stats.test          | 3 +++
 mysql-test/main/opt_trace_index_merge.test            | 1 +
 mysql-test/main/opt_trace_ucs2.test                   | 2 ++
 mysql-test/main/optimizer_costs.test                  | 2 ++
 mysql-test/main/order_by_sortkey.test                 | 1 +
 mysql-test/main/partition_explicit_prune.test         | 1 +
 mysql-test/main/ps.test                               | 1 +
 mysql-test/main/range_notembedded.test                | 2 ++
 mysql-test/main/sargable_casefold_notembedded.test    | 1 +
 mysql-test/main/spatial_utility_function_geohash.test | 1 +
 mysql-test/main/symlink-aria-11902.test               | 1 +
 mysql-test/main/symlink-myisam-11902.test             | 1 +
 mysql-test/main/tmp_table_count-7586.test             | 2 ++
 mysql-test/main/udf.test                              | 1 +
 24 files changed, 46 insertions(+)

diff --git a/mysql-test/main/create.test b/mysql-test/main/create.test
index 42bf890cb7510..d088fe2b50128 100644
--- a/mysql-test/main/create.test
+++ b/mysql-test/main/create.test
@@ -398,6 +398,7 @@ select
     ifnull(h,cast('yet another binary data' as binary))   as h,
     addtime(cast('1:0:0' as time),cast('1:0:0' as time))  as dd
 from t1;
+--disable_replay next_query This is EXPLAIN TABLE.
 explain t2;
 select * from t2;
 drop table t1, t2;
diff --git a/mysql-test/main/desc_index_range.test b/mysql-test/main/desc_index_range.test
index 36f4c406dc39c..b158353bee65b 100644
--- a/mysql-test/main/desc_index_range.test
+++ b/mysql-test/main/desc_index_range.test
@@ -14,6 +14,7 @@ create table t1 (
 insert into t1 select seq from seq_1_to_1000;
 
 set optimizer_trace=1;
+--disable_replay next_query Need to preserve optimizer trace
 explain select * from t1 force index(a) where a in (2, 4, 6);
 
 #Enable after fix MDEV-32034
@@ -39,6 +40,7 @@ create table t1 (
 insert into t1 select A.seq, B.seq*10 from seq_1_to_10 A, seq_1_to_10 B;
 
 set optimizer_trace=1;
+--disable_replay next_query Need to preserve optimizer trace
 explain select * from t1 force index(ab) where a>=8 and b>=50;
 #Enable after fix MDEV-32034
 --disable_view_protocol
@@ -46,6 +48,7 @@ select json_detailed(json_extract(trace, '$**.range_access_plan.ranges')) as jd
 from information_schema.optimizer_trace;
 --enable_view_protocol
 
+--disable_replay next_query Need to preserve optimizer trace
 explain select * from t1 force index(ab) where a>=8 and b<=50;
 #Enable after fix MDEV-32034
 --disable_view_protocol
@@ -56,6 +59,7 @@ from information_schema.optimizer_trace;
 select * from t1 force index(ab) where a>=8 and b<=50;
 select * from t1 ignore index(ab) where a>=8 and b<=50 order by a, b desc;
 
+--disable_replay next_query Need to preserve optimizer trace
 explain
 select * from t1 where a between 2 and 4 and b between 50 and 80;
 #Enable after fix MDEV-32034
@@ -75,6 +79,7 @@ create table t2 (
 );
 insert into t2 select A.seq, B.seq*10 from seq_1_to_10 A, seq_1_to_10 B;
 
+--disable_replay next_query Need to preserve optimizer trace
 explain
 select * from t2 where a between 2 and 4;
 #Enable after fix MDEV-32034
@@ -83,6 +88,7 @@ select json_detailed(json_extract(trace, '$**.range_access_plan.ranges')) as jd
 from information_schema.optimizer_trace;
 --enable_view_protocol
 
+--disable_replay next_query Need to preserve optimizer trace
 explain
 select * from t2 where a between 2 and 4 and b between 50 and 80;
 #Enable after fix MDEV-32034
@@ -99,6 +105,7 @@ drop table t2;
 --echo #
 CREATE TABLE t1 (p int NOT NULL, a int NOT NULL, PRIMARY KEY (p,a desc));
 insert into t1 select 2,seq from seq_0_to_1000;
+--disable_replay next_query Need to preserve optimizer trace
 EXPLAIN select MIN(a) from t1 where p = 2 group by p;
 #Enable after fix MDEV-32034
 --disable_view_protocol
diff --git a/mysql-test/main/distinct_notembedded.test b/mysql-test/main/distinct_notembedded.test
index 84d39f975a6e0..f4125ca204410 100644
--- a/mysql-test/main/distinct_notembedded.test
+++ b/mysql-test/main/distinct_notembedded.test
@@ -45,6 +45,7 @@ eval $trace;
 SELECT AVG(DISTINCT b / a) FROM t1;
 eval $trace;
 
+--disable_replay next_query Need to preserve optimizer trace
 EXPLAIN SELECT COUNT(DISTINCT (SELECT a)) FROM t1;
 eval $trace;
 
diff --git a/mysql-test/main/explain_json.test b/mysql-test/main/explain_json.test
index 0d34b95070426..56ecf3c7d3f27 100644
--- a/mysql-test/main/explain_json.test
+++ b/mysql-test/main/explain_json.test
@@ -141,6 +141,8 @@ select * from t1 where a in (select max(a) from t1 group by b);
 create table t2 like t1;
 insert into t2 select * from t1;
 --source include/explain-no-costs.inc
+
+--disable_replay next_query Will try to create table for sequence engine
 explain format=json
 select * from t1,t2 where t1.a in ( select seq+0 from seq_1_to_100);
 
diff --git a/mysql-test/main/greedy_optimizer.test b/mysql-test/main/greedy_optimizer.test
index 34b5a571682b5..365058b01f07d 100644
--- a/mysql-test/main/greedy_optimizer.test
+++ b/mysql-test/main/greedy_optimizer.test
@@ -1,5 +1,7 @@
 --source include/have_innodb.inc
 
+--disable_replay testfile Uses Last_query_cost and counters for most queries.
+
 #
 # A simple test of the greedy query optimization algorithm and the switches that
 # controls the optimization process.
diff --git a/mysql-test/main/index_merge_innodb_notembedded.test b/mysql-test/main/index_merge_innodb_notembedded.test
index eb38108562f35..78bb6471dd003 100644
--- a/mysql-test/main/index_merge_innodb_notembedded.test
+++ b/mysql-test/main/index_merge_innodb_notembedded.test
@@ -24,6 +24,7 @@ INSERT INTO t1(id,title,status,country_code)
 SELECT seq, CONCAT('abc', seq), seq%10, CONCAT('C', seq%5) FROM seq_1_to_500;
 
 --echo # This must not use index_merge:
+--disable_replay next_query Need to preserve optimizer trace
 EXPLAIN
 SELECT * FROM t1 WHERE country_code ='C1' and `status` =1;
 set @trace= (select JSON_EXTRACT(trace, '$**.range_scan_alternatives[*]')
@@ -50,6 +51,7 @@ INSERT INTO t1(id,title,status,country_code)
 SELECT seq, CONCAT('abc', seq), seq%10, CONCAT('C', seq%5) FROM seq_1_to_500;
 
 --echo # Must not use index_merge:
+--disable_replay next_query Need to preserve optimizer trace
 EXPLAIN
 SELECT * FROM t1 WHERE country_code ='C1' and status = 1;
 
@@ -75,6 +77,7 @@ INSERT INTO t1(id,title,status,country_code)
 SELECT seq, CONCAT('abc', seq), seq%10, CONCAT('C', seq%5) FROM seq_1_to_500;
 
 --echo # Must not use index_merge:
+--disable_replay next_query Need to preserve optimizer trace
 EXPLAIN
 SELECT * FROM t1 WHERE country_code ='C1' and status = 1;
 
diff --git a/mysql-test/main/join.test b/mysql-test/main/join.test
index efdbf6724d963..1413d25aedca6 100644
--- a/mysql-test/main/join.test
+++ b/mysql-test/main/join.test
@@ -663,6 +663,7 @@ flush status;
 --disable_ps2_protocol
 select * from t1, t2, t3 where t3.a=t1.a and t2.a=t1.b;
 --enable_ps2_protocol
+--disable_replay testfile Need to preserve counters
 explain select * from t1, t2, t3 where t3.a=t1.a and t2.a=t1.b;
 --echo We expect rnd_next=5, and read_key must be 0 because of short-cutting:
 show status like 'Handler_read%'; 
@@ -695,6 +696,7 @@ insert into t1 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
 create table t2 (a int, b int, primary key(a));
 insert into t2 select @v:=A.a+10*B.a, @v  from t1 A, t1 B;
 
+--disable_replay testfile Need to preserve counters
 explain select * from t1;
 show status like 'Last_query_cost';
 select 'The cost of accessing t1 (dont care if it changes' '^';
@@ -703,6 +705,7 @@ select 'vv: Following query must use ALL(t1), eq_ref(A), eq_ref(B): vv' Z;
 
 select @@myisam.optimizer_disk_read_ratio;
 set global myisam.optimizer_disk_read_ratio=0;
+--disable_replay testfile Need to preserve counters
 explain select * from t1, t2 A, t2 B where A.a = t1.a and B.a=A.b;
 show status like 'Last_query_cost';
 select '^^: The above should be ~= 40 + cost(select * from t1). Value less than 40 is an error' Z;
diff --git a/mysql-test/main/join_cache_cardinality.test b/mysql-test/main/join_cache_cardinality.test
index b178810b80764..9a0e9bb52fba8 100644
--- a/mysql-test/main/join_cache_cardinality.test
+++ b/mysql-test/main/join_cache_cardinality.test
@@ -1,5 +1,7 @@
 --source include/have_sequence.inc
 
+--disable_replay testfile Uses Optimizer Trace for most queries.
+
 # Embedded doesn't have optimizer trace:
 --source include/not_embedded.inc
 
diff --git a/mysql-test/main/opt_context_load_stats_basic.test b/mysql-test/main/opt_context_load_stats_basic.test
index 2233e2b7c9f8a..146bfe0458cef 100644
--- a/mysql-test/main/opt_context_load_stats_basic.test
+++ b/mysql-test/main/opt_context_load_stats_basic.test
@@ -1,6 +1,9 @@
 --source include/not_embedded.inc
 --source include/have_sequence.inc
 --echo #enable optimizer_record_context
+
+--disable_replay testfile Don't replay a replay test
+
 set optimizer_record_context=ON;
 set @saved_opt_context_var_name_1= 'saved_opt_context_1';
 set @saved_opt_context_var_name_2= 'saved_opt_context_2';
diff --git a/mysql-test/main/opt_context_replay_basic.test b/mysql-test/main/opt_context_replay_basic.test
index fa1d6fba3c8c0..15ca7889971d6 100644
--- a/mysql-test/main/opt_context_replay_basic.test
+++ b/mysql-test/main/opt_context_replay_basic.test
@@ -4,6 +4,8 @@
 --echo #enable optimizer_record_context
 set optimizer_record_context=ON;
 
+--disable_replay testfile Don't replay a replay test
+
 create database db1;
 use db1;
 
diff --git a/mysql-test/main/opt_context_store_stats.test b/mysql-test/main/opt_context_store_stats.test
index 4c25c0f95a44d..f34af00f11cf4 100644
--- a/mysql-test/main/opt_context_store_stats.test
+++ b/mysql-test/main/opt_context_store_stats.test
@@ -1,6 +1,9 @@
 --source include/not_embedded.inc
 --source include/have_sequence.inc
 --echo #enable optimizer_record_context
+
+--disable_replay testfile Don't replay a replay test
+
 set optimizer_record_context=ON;
 
 create database db1;
diff --git a/mysql-test/main/opt_trace_index_merge.test b/mysql-test/main/opt_trace_index_merge.test
index 3cc54f5342867..d2b05cd9bf2d7 100644
--- a/mysql-test/main/opt_trace_index_merge.test
+++ b/mysql-test/main/opt_trace_index_merge.test
@@ -1,4 +1,5 @@
 --source include/not_embedded.inc
+--disable_replay testfile Need to preserve optimizer trace
 set @tmp_opt_switch= @@optimizer_switch;
 set optimizer_switch='index_merge_sort_intersection=on';
 set optimizer_trace='enabled=on';
diff --git a/mysql-test/main/opt_trace_ucs2.test b/mysql-test/main/opt_trace_ucs2.test
index 7a26eefc4d6de..0b6b9b142c26c 100644
--- a/mysql-test/main/opt_trace_ucs2.test
+++ b/mysql-test/main/opt_trace_ucs2.test
@@ -1,6 +1,8 @@
 --source include/not_embedded.inc
 --source include/have_ucs2.inc
 
+--disable_replay testfile Need to preserve optimizer trace
+
 create or replace table t1 (col1 char(10) character set ucs2, filler char(100), key(col1)) ;
 insert into t1 values ('a', 'a');
 insert into t1 values ('a', 'a');
diff --git a/mysql-test/main/optimizer_costs.test b/mysql-test/main/optimizer_costs.test
index bd7e89a58cc01..39d5ddc9af82c 100644
--- a/mysql-test/main/optimizer_costs.test
+++ b/mysql-test/main/optimizer_costs.test
@@ -147,12 +147,14 @@ create table t1 (l_orderkey int(11) NOT NULL,
                  l_suppkey int(11) DEFAULT NULL,
                  PRIMARY KEY (l_orderkey)) engine=aria;
 insert into t1 select seq,seq,seq from seq_1_to_1000;
+--disable_replay next_query Will try to create table for sequence engine
 explain select straight_join count(*) from seq_1_to_10000,t1 where seq=l_orderkey;
 show status like "last_query_cost";
 set @org_cost=@@aria.optimizer_key_next_find_cost;
 # Set cost for t1 high so that we cannot use it for index scans
 set global aria.optimizer_key_next_find_cost=1000;
 flush tables;
+--disable_replay next_query Will try to create table for sequence engine
 explain select count(*) from seq_1_to_10000,t1 where seq=l_orderkey;
 show status like "last_query_cost";
 set global aria.optimizer_key_next_find_cost=@org_cost;
diff --git a/mysql-test/main/order_by_sortkey.test b/mysql-test/main/order_by_sortkey.test
index 1fb18aa0e0111..0cac888f420f0 100644
--- a/mysql-test/main/order_by_sortkey.test
+++ b/mysql-test/main/order_by_sortkey.test
@@ -59,6 +59,7 @@ FLUSH STATUS;
 SHOW SESSION STATUS LIKE 'Sort%';
 
 --disable_ps2_protocol
+--disable_replay next_query Needs to preserve counters
 explain SELECT * FROM t1 ORDER BY f2 LIMIT 100;
 SELECT * FROM t1 ORDER BY f2 LIMIT 100;
 --enable_ps2_protocol
diff --git a/mysql-test/main/partition_explicit_prune.test b/mysql-test/main/partition_explicit_prune.test
index bd42af70aa2a0..300b235dc79c4 100644
--- a/mysql-test/main/partition_explicit_prune.test
+++ b/mysql-test/main/partition_explicit_prune.test
@@ -258,6 +258,7 @@ eval $get_handler_status_counts;
 EXPLAIN PARTITIONS SELECT * FROM t1 PARTITION (pNonexistent);
 EXPLAIN PARTITIONS SELECT * FROM t1 PARTITION (subp2);
 FLUSH STATUS;
+--disable_replay testfile Need to preserve counters
 EXPLAIN PARTITIONS SELECT * FROM t1 PARTITION (subp2,pNeg) AS TableAlias;
 eval $get_handler_status_counts;
 --echo # 8 locks (1 ha_partition + 3 ha_innobase) x 2 (lock/unlock)
diff --git a/mysql-test/main/ps.test b/mysql-test/main/ps.test
index ed213f1da7761..6b803c0b5202e 100644
--- a/mysql-test/main/ps.test
+++ b/mysql-test/main/ps.test
@@ -4989,6 +4989,7 @@ CREATE TABLE t1 (c int);
 CREATE TABLE t2 (d int);
 
 --echo # EXPLAIN EXTENDED in regular way (not PS mode)
+--disable_replay testfile Need to preserve warnings
 EXPLAIN EXTENDED SELECT (SELECT 1 FROM t2 WHERE d = c) FROM t1;
 SHOW WARNINGS;
 
diff --git a/mysql-test/main/range_notembedded.test b/mysql-test/main/range_notembedded.test
index a13bb1d95c79a..7bb9abd01079e 100644
--- a/mysql-test/main/range_notembedded.test
+++ b/mysql-test/main/range_notembedded.test
@@ -8,6 +8,8 @@
 drop table if exists t1,t2;
 --enable_warnings
 
+--disable_replay testfile Need to preserve optimizer trace
+
 --echo #
 --echo # MDEV-21958: Query having many NOT-IN clauses running forever
 --echo #
diff --git a/mysql-test/main/sargable_casefold_notembedded.test b/mysql-test/main/sargable_casefold_notembedded.test
index b04e25f1cac22..6502c5bb6e8ec 100644
--- a/mysql-test/main/sargable_casefold_notembedded.test
+++ b/mysql-test/main/sargable_casefold_notembedded.test
@@ -6,6 +6,7 @@
 --source include/not_embedded.inc
 --source include/have_sequence.inc
 
+--disable_replay testfile Need to preserve optimizer trace
 
 create table t1 (
   col1 varchar(32), 
diff --git a/mysql-test/main/spatial_utility_function_geohash.test b/mysql-test/main/spatial_utility_function_geohash.test
index 4d40e6302eedc..6d5ace7101ccf 100644
--- a/mysql-test/main/spatial_utility_function_geohash.test
+++ b/mysql-test/main/spatial_utility_function_geohash.test
@@ -632,6 +632,7 @@ SELECT ST_ASTEXT(ST_POINTFROMGEOHASH(hash_value,0)) FROM geohashes;
 
 --echo # Test create table from SELECT statement
 CREATE TABLE t1 AS SELECT ST_POINTFROMGEOHASH("0123", 4326);
+--disable_replay next_query This is EXPLAIN TABLE.
 EXPLAIN t1;
 DROP TABLE t1;
 
diff --git a/mysql-test/main/symlink-aria-11902.test b/mysql-test/main/symlink-aria-11902.test
index a2a266cbb2544..35f95ec76367f 100644
--- a/mysql-test/main/symlink-aria-11902.test
+++ b/mysql-test/main/symlink-aria-11902.test
@@ -1,6 +1,7 @@
 #
 # MDEV-11902 mi_open race condition
 #
+--disable_replay testfile Don't support symlink tables
 source include/have_maria.inc;
 set default_storage_engine=Aria;
 source symlink-myisam-11902.test;
diff --git a/mysql-test/main/symlink-myisam-11902.test b/mysql-test/main/symlink-myisam-11902.test
index c782ef44ec54f..c1a2556078591 100644
--- a/mysql-test/main/symlink-myisam-11902.test
+++ b/mysql-test/main/symlink-myisam-11902.test
@@ -1,6 +1,7 @@
 #
 # MDEV-11902 mi_open race condition
 #
+--disable_replay testfile Don't support symlink tables
 source include/have_debug_sync.inc;
 source include/have_symlink.inc;
 source include/not_windows.inc;
diff --git a/mysql-test/main/tmp_table_count-7586.test b/mysql-test/main/tmp_table_count-7586.test
index ff93a25039f70..fdcbe931a7b58 100644
--- a/mysql-test/main/tmp_table_count-7586.test
+++ b/mysql-test/main/tmp_table_count-7586.test
@@ -3,6 +3,8 @@
 --source include/have_perfschema.inc
 --source include/not_embedded.inc
 
+--disable_replay testfile Need to preserve counters
+
 # Tests will be skipped for the view protocol because the view protocol creates 
 # an additional util connection and other statistics data
 -- source include/no_view_protocol.inc
diff --git a/mysql-test/main/udf.test b/mysql-test/main/udf.test
index 7d5712beb9fe5..95767a508dd8e 100644
--- a/mysql-test/main/udf.test
+++ b/mysql-test/main/udf.test
@@ -5,6 +5,7 @@
 # the library are.
 #
 
+--disable_replay testfile Don't support UDFs
 
 --disable_warnings
 drop table if exists t1;

From 42913902fc793a6841f8abf438fa64a679d7d68f Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 24 Apr 2026 22:32:44 +0300
Subject: [PATCH 32/50] MDEV-39368: Make --replay-server-manual also provide a
 gdb include file.

---
 mysql-test/lib/start_extra_server.pl |  1 +
 mysql-test/mariadb-test-run.pl       | 12 ++++++++++++
 2 files changed, 13 insertions(+)

diff --git a/mysql-test/lib/start_extra_server.pl b/mysql-test/lib/start_extra_server.pl
index 07dfc556575e9..ab9ac4b43b449 100755
--- a/mysql-test/lib/start_extra_server.pl
+++ b/mysql-test/lib/start_extra_server.pl
@@ -83,6 +83,7 @@
     "--key-buffer-size=1M",
     "--sort-buffer-size=256K",
     "--max-heap-table-size=1M",
+    "--gdb",
 );
 
 print "Starting mysqld on port $port with socket $socket...\n";
diff --git a/mysql-test/mariadb-test-run.pl b/mysql-test/mariadb-test-run.pl
index 54835ca294324..e1988279b968e 100755
--- a/mysql-test/mariadb-test-run.pl
+++ b/mysql-test/mariadb-test-run.pl
@@ -3374,8 +3374,17 @@ sub start_replay_server_manual {
     "--key-buffer-size=1M",
     "--sort-buffer-size=256K",
     "--max-heap-table-size=1M",
+    "--gdb",
   );
   
+  # Write a gdb init file so the user can run:
+  #   gdb -x var/tmp/gdbinit-replay <mysqld>
+  # The file contains a single "set args ..." line with all mysqld arguments
+  # (excluding the mysqld binary itself, which gdb takes separately).
+  my $gdbinit_file = "$opt_vardir/tmp/gdbinit-replay";
+  mtr_tofile($gdbinit_file,
+             "set args " . join(" ", @mysqld_args[1 .. $#mysqld_args]) . "\n");
+
   # Print command line for user
   mtr_report("=" x 70);
   mtr_report("REPLAY SERVER MANUAL MODE");
@@ -3388,6 +3397,9 @@ sub start_replay_server_manual {
   mtr_report("Or run under gdb:");
   mtr_report("gdb --args " . join(" \\\n  ", @mysqld_args));
   mtr_report("");
+  mtr_report("gdb init file written to: $gdbinit_file");
+  mtr_report("    gdb -x $gdbinit_file $mysqld");
+  mtr_report("");
   mtr_report("Waiting for socket file to appear: $socket");
   mtr_report("(Timeout: 300 seconds)");
   mtr_report("=" x 70);

From 728337109a8d77452c531b86ff73b8bd5e1d718b Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Sun, 26 Apr 2026 15:37:03 +0300
Subject: [PATCH 33/50] MDEV-39435: Context Replay : Assertion `table_records
 || !head->file->stats.records' failed

The problem was caused by this scenario:
- The same table can be used multiple times in the query.
- A SELECT may be resolved without ever entering make_join_statistics()
  and set_statistics_for_table(). This will happen if the SELECT is
  handled via opt_sum_query, for example.
- Then, Context Capture code can take this TABLE object and save its
  unitialized statistics into the Optimizer Context.
- When we then attempt to use unitialized statistics in the other
  SELECT that is handled in regular way, we get a failure.

The fix:
- Do not save/restore table->used_stat_records. Do save/restore
  table->file->stats.records and let the SQL layer to copy it to
  used_stat_records (or use EITS data).
---
 .../get_rec_idx_ranges_from_opt_ctx.inc       |   4 +-
 mysql-test/include/opt_context_schema.inc     |   2 +-
 .../main/opt_context_load_stats_basic.result  |  61 +++++-----
 .../main/opt_context_load_stats_basic.test    |  10 +-
 .../main/opt_context_replay_basic.result      |  18 ++-
 mysql-test/main/opt_context_replay_basic.test |  24 ++++
 .../main/opt_context_store_stats.result       |  62 +++++-----
 sql/opt_context_store_replay.cc               | 109 ++++++++----------
 sql/opt_context_store_replay.h                |   2 +-
 sql/sql_statistics.cc                         |  10 ++
 10 files changed, 173 insertions(+), 129 deletions(-)

diff --git a/mysql-test/include/get_rec_idx_ranges_from_opt_ctx.inc b/mysql-test/include/get_rec_idx_ranges_from_opt_ctx.inc
index 2f3bffa1d1c49..7e0a363c8af34 100644
--- a/mysql-test/include/get_rec_idx_ranges_from_opt_ctx.inc
+++ b/mysql-test/include/get_rec_idx_ranges_from_opt_ctx.inc
@@ -4,9 +4,9 @@ set @opt_context=
          '(?<=set @opt_context=\')([\n\r].*)*(?=\'\;#opt_context_ends)')
          from information_schema.optimizer_context);
 set @records=
-    (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+    (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 select *from json_table(@records,
-                        '$[*]' columns(num_of_records text path '$')) as jt;
+                        '$[*]' columns(file_stat_records text path '$')) as jt;
 set @file_stat_records=
     (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 select *from json_table(@file_stat_records,
diff --git a/mysql-test/include/opt_context_schema.inc b/mysql-test/include/opt_context_schema.inc
index c7731e69cfe66..855f988eb5aa4 100644
--- a/mysql-test/include/opt_context_schema.inc
+++ b/mysql-test/include/opt_context_schema.inc
@@ -14,7 +14,7 @@ let $opt_context_schema=
             "type": "string",
             "minLength": 1
           },
-          "num_of_records": {
+          "file_stat_records": {
             "type": "number"
           },
           "file_stat_records": {
diff --git a/mysql-test/main/opt_context_load_stats_basic.result b/mysql-test/main/opt_context_load_stats_basic.result
index f6250af5faa45..b07657d877794 100644
--- a/mysql-test/main/opt_context_load_stats_basic.result
+++ b/mysql-test/main/opt_context_load_stats_basic.result
@@ -32,10 +32,10 @@ context,
 '(?<=set @opt_context=\')([\n\r].*)*(?=\'\;#opt_context_ends)')
 from information_schema.optimizer_context);
 set @records=
-(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 select *from json_table(@records,
-'$[*]' columns(num_of_records text path '$')) as jt;
-num_of_records
+'$[*]' columns(file_stat_records text path '$')) as jt;
+file_stat_records
 20
 set @file_stat_records=
 (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
@@ -129,7 +129,7 @@ from information_schema.optimizer_context);
 select JSON_EQUALS(@saved_opt_context_1, @opt_context);
 JSON_EQUALS(@saved_opt_context_1, @opt_context)
 0
-set @records= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+set @records= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 set @indexes=(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.indexes')));
 set @list_ranges= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.list_ranges')));
 set @saved_records_2 = @records;
@@ -138,8 +138,8 @@ set @saved_list_ranges_2 = @list_ranges;
 select JSON_EQUALS(@saved_records_2, @saved_records_1);
 JSON_EQUALS(@saved_records_2, @saved_records_1)
 0
-select * from json_table(@records, '$[*]' columns(num_of_records text path '$')) as jt;
-num_of_records
+select * from json_table(@records, '$[*]' columns(file_stat_records text path '$')) as jt;
+file_stat_records
 40
 select JSON_EQUALS(@saved_indexes_2, @saved_indexes_1);
 JSON_EQUALS(@saved_indexes_2, @saved_indexes_1)
@@ -240,7 +240,7 @@ from information_schema.optimizer_context);
 select JSON_EQUALS(@saved_opt_context_1, @opt_context);
 JSON_EQUALS(@saved_opt_context_1, @opt_context)
 0
-set @records= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+set @records= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 set @indexes=(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.indexes')));
 set @list_ranges= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.list_ranges')));
 select JSON_EQUALS(@saved_records_2, @records);
@@ -273,7 +273,7 @@ set @opt_context=
 context,
 '(?<=set @opt_context=\')([\n\r].*)*(?=\'\;#opt_context_ends)')
 from information_schema.optimizer_context);
-set @records= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+set @records= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 set @indexes=(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.indexes')));
 set @list_ranges= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.list_ranges')));
 select JSON_EQUALS(@saved_records_2, @records);
@@ -343,18 +343,18 @@ set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].name');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "name" element not present at offset 1409.
+Warning	4253	Failed to parse saved optimizer context: "name" element not present at offset 1387.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].ddl');
 select * from t1 where a > 10;
 a	b
 Warnings:
 Warning	4254	Failed to match the stats from replay context with the optimizer stats: the given list of ranges i.e. [(10) < (a), ] doesn't exist in the list of ranges for table_name db1.t1 and index_name t1_idx_a
 Warning	4254	Failed to match the stats from replay context with the optimizer stats: the given list of ranges i.e. [(10) < (a), ] doesn't exist in the list of ranges for table_name db1.t1 and index_name t1_idx_ab
-set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].num_of_records');
+set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].file_stat_records');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "num_of_records" element not present at offset 1405.
+Warning	4253	Failed to parse saved optimizer context: "file_stat_records" element not present at offset 1380.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].file_stat_records');
 select * from t1 where a > 10;
 a	b
@@ -364,42 +364,42 @@ set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].indexes[0
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "index_name" element not present at offset 166.
+Warning	4253	Failed to parse saved optimizer context: "index_name" element not present at offset 144.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].indexes[0].rec_per_key');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "rec_per_key" element not present at offset 170.
+Warning	4253	Failed to parse saved optimizer context: "rec_per_key" element not present at offset 148.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_ranges[0].index_name');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "index_name" element not present at offset 643.
+Warning	4253	Failed to parse saved optimizer context: "index_name" element not present at offset 621.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_ranges[0].ranges');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "ranges" element not present at offset 635.
+Warning	4253	Failed to parse saved optimizer context: "ranges" element not present at offset 613.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_ranges[0].num_rows');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "num_rows" element not present at offset 653.
+Warning	4253	Failed to parse saved optimizer context: "num_rows" element not present at offset 631.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_ranges[0].cost');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "cost" element not present at offset 437.
+Warning	4253	Failed to parse saved optimizer context: "cost" element not present at offset 415.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_ranges[0].max_index_blocks');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "max_index_blocks" element not present at offset 646.
+Warning	4253	Failed to parse saved optimizer context: "max_index_blocks" element not present at offset 624.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_ranges[0].max_row_blocks');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "max_row_blocks" element not present at offset 648.
+Warning	4253	Failed to parse saved optimizer context: "max_row_blocks" element not present at offset 626.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].indexes[0]');
 select * from t1 where a > 10;
 a	b
@@ -418,6 +418,9 @@ select * from t1 where a > 10;
 a	b
 Warnings:
 Warning	4254	Failed to match the stats from replay context with the optimizer stats: db1.t1 doesn't exist in list of table contexts
+Warning	4254	Failed to match the stats from replay context with the optimizer stats: db1.t1.t1_idx_a doesn't exist in list of index contexts
+Warning	4254	Failed to match the stats from replay context with the optimizer stats: db1.t1.t1_idx_b doesn't exist in list of index contexts
+Warning	4254	Failed to match the stats from replay context with the optimizer stats: db1.t1.t1_idx_ab doesn't exist in list of index contexts
 Warning	4254	Failed to match the stats from replay context with the optimizer stats: db1.t1 doesn't exist in list of table contexts
 Warning	4254	Failed to match the stats from replay context with the optimizer stats: db1.t1.t1_idx_a doesn't exist in list of range contexts
 Warning	4254	Failed to match the stats from replay context with the optimizer stats: db1.t1.t1_idx_ab doesn't exist in list of range contexts
@@ -438,51 +441,51 @@ set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_inde
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "key_number" element not present at offset 535.
+Warning	4253	Failed to parse saved optimizer context: "key_number" element not present at offset 513.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_index_read_costs[0].num_records');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "num_records" element not present at offset 534.
+Warning	4253	Failed to parse saved optimizer context: "num_records" element not present at offset 512.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_index_read_costs[0].eq_ref');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "eq_ref" element not present at offset 539.
+Warning	4253	Failed to parse saved optimizer context: "eq_ref" element not present at offset 517.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_index_read_costs[0].index_cost_io');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "index_cost_io" element not present at offset 532.
+Warning	4253	Failed to parse saved optimizer context: "index_cost_io" element not present at offset 510.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_index_read_costs[0].index_cost_cpu');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "index_cost_cpu" element not present at offset 521.
+Warning	4253	Failed to parse saved optimizer context: "index_cost_cpu" element not present at offset 499.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_index_read_costs[0].row_cost_io');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "row_cost_io" element not present at offset 534.
+Warning	4253	Failed to parse saved optimizer context: "row_cost_io" element not present at offset 512.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_index_read_costs[0].row_cost_cpu');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "row_cost_cpu" element not present at offset 523.
+Warning	4253	Failed to parse saved optimizer context: "row_cost_cpu" element not present at offset 501.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_index_read_costs[0].max_index_blocks');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "max_index_blocks" element not present at offset 529.
+Warning	4253	Failed to parse saved optimizer context: "max_index_blocks" element not present at offset 507.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_index_read_costs[0].max_row_blocks');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "max_row_blocks" element not present at offset 531.
+Warning	4253	Failed to parse saved optimizer context: "max_row_blocks" element not present at offset 509.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_index_read_costs[0].copy_cost');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "copy_cost" element not present at offset 536.
+Warning	4253	Failed to parse saved optimizer context: "copy_cost" element not present at offset 514.
 drop table t1;
 drop database db1;
diff --git a/mysql-test/main/opt_context_load_stats_basic.test b/mysql-test/main/opt_context_load_stats_basic.test
index 146bfe0458cef..323648fe625cd 100644
--- a/mysql-test/main/opt_context_load_stats_basic.test
+++ b/mysql-test/main/opt_context_load_stats_basic.test
@@ -79,7 +79,7 @@ select * from t1 where a < 3 and b > 6;
 
 select JSON_EQUALS(@saved_opt_context_1, @opt_context);
 
-set @records= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+set @records= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 set @indexes=(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.indexes')));
 set @list_ranges= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.list_ranges')));
 
@@ -88,7 +88,7 @@ set @saved_indexes_2 = @indexes;
 set @saved_list_ranges_2 = @list_ranges;
 
 select JSON_EQUALS(@saved_records_2, @saved_records_1);
-select * from json_table(@records, '$[*]' columns(num_of_records text path '$')) as jt;
+select * from json_table(@records, '$[*]' columns(file_stat_records text path '$')) as jt;
 select JSON_EQUALS(@saved_indexes_2, @saved_indexes_1);
 select JSON_EQUALS(@saved_list_ranges_2, @saved_list_ranges_1);
 select * from json_table(
@@ -153,7 +153,7 @@ select * from t1 where a < 3 and b > 6;
 
 select JSON_EQUALS(@saved_opt_context_1, @opt_context);
 
-set @records= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+set @records= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 set @indexes=(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.indexes')));
 set @list_ranges= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.list_ranges')));
 
@@ -174,7 +174,7 @@ select * from t1 where a < 3 and b > 6;
 
 --source include/get_opt_context.inc
 
-set @records= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+set @records= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 set @indexes=(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.indexes')));
 set @list_ranges= (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.list_ranges')));
 
@@ -223,7 +223,7 @@ select * from t1 where a > 10;
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].ddl');
 select * from t1 where a > 10;
 
-set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].num_of_records');
+set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].file_stat_records');
 select * from t1 where a > 10;
 
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].file_stat_records');
diff --git a/mysql-test/main/opt_context_replay_basic.result b/mysql-test/main/opt_context_replay_basic.result
index 33b483fee625c..fa2f610832add 100644
--- a/mysql-test/main/opt_context_replay_basic.result
+++ b/mysql-test/main/opt_context_replay_basic.result
@@ -136,7 +136,6 @@ set @opt_context='
   "list_contexts": [
     {
       "name": "db1.t1",
-      "num_of_records": 0,
       "file_stat_records": 20,
       "read_cost_io": 0,
       "read_cost_cpu": 0.0100356,
@@ -234,5 +233,22 @@ EXPLAIN
     ]
   }
 }
+set optimizer_replay_context='';
+drop table t1;
+#
+# MDEV-39435: Server crash : Assertion `table_records || !head->file->stats.records' failed
+#
+CREATE TABLE t1 (a INT, PRIMARY KEY(a));
+INSERT INTO t1 VALUES (1),(2),(3);
+set optimizer_record_context=ON;
+EXPLAIN SELECT * FROM t1 WHERE a IN
+((SELECT MAX(a) FROM t1), (SELECT MAX(a) FROM t1));
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	range	PRIMARY	PRIMARY	4	NULL	1	Using where; Using index
+3	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
+2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
+select context into dumpfile "../../tmp/dump1.sql"
+from information_schema.optimizer_context;
+drop table t1;
 drop table t1;
 drop database db1;
diff --git a/mysql-test/main/opt_context_replay_basic.test b/mysql-test/main/opt_context_replay_basic.test
index 15ca7889971d6..d14017d17824f 100644
--- a/mysql-test/main/opt_context_replay_basic.test
+++ b/mysql-test/main/opt_context_replay_basic.test
@@ -68,5 +68,29 @@ set optimizer_replay_context='opt_context';
 --echo # Same query as above, must have same explain:
 EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE a = 1;
 
+set optimizer_replay_context='';
+--remove_file "$MYSQLTEST_VARDIR/tmp/dump1.sql"
 drop table t1;
+
+--echo #
+--echo # MDEV-39435: Server crash : Assertion `table_records || !head->file->stats.records' failed
+--echo #
+CREATE TABLE t1 (a INT, PRIMARY KEY(a));
+INSERT INTO t1 VALUES (1),(2),(3);
+
+set optimizer_record_context=ON;
+EXPLAIN SELECT * FROM t1 WHERE a IN
+  ((SELECT MAX(a) FROM t1), (SELECT MAX(a) FROM t1));
+select context into dumpfile "../../tmp/dump1.sql"
+from information_schema.optimizer_context;
+drop table t1;
+
+--disable_query_log
+--disable_result_log
+--source "$MYSQLTEST_VARDIR/tmp/dump1.sql"
+--enable_query_log
+--enable_result_log
+
+drop table t1;
+
 drop database db1;
diff --git a/mysql-test/main/opt_context_store_stats.result b/mysql-test/main/opt_context_store_stats.result
index 569e74319629b..d09e53620358b 100644
--- a/mysql-test/main/opt_context_store_stats.result
+++ b/mysql-test/main/opt_context_store_stats.result
@@ -40,11 +40,11 @@ context,
 '(?<=set @opt_context=\')([\n\r].*)*(?=\'\;#opt_context_ends)')
 from information_schema.optimizer_context);
 set @records=
-(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 select *from json_table(@records,
-'$[*]' columns(num_of_records text path '$')) as jt;
-num_of_records
-0
+'$[*]' columns(file_stat_records text path '$')) as jt;
+file_stat_records
+20
 set @file_stat_records=
 (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 select *from json_table(@file_stat_records,
@@ -85,10 +85,10 @@ context,
 '(?<=set @opt_context=\')([\n\r].*)*(?=\'\;#opt_context_ends)')
 from information_schema.optimizer_context);
 set @records=
-(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 select *from json_table(@records,
-'$[*]' columns(num_of_records text path '$')) as jt;
-num_of_records
+'$[*]' columns(file_stat_records text path '$')) as jt;
+file_stat_records
 30
 20
 set @file_stat_records=
@@ -136,10 +136,10 @@ context,
 '(?<=set @opt_context=\')([\n\r].*)*(?=\'\;#opt_context_ends)')
 from information_schema.optimizer_context);
 set @records=
-(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 select *from json_table(@records,
-'$[*]' columns(num_of_records text path '$')) as jt;
-num_of_records
+'$[*]' columns(file_stat_records text path '$')) as jt;
+file_stat_records
 set @file_stat_records=
 (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 select *from json_table(@file_stat_records,
@@ -173,10 +173,10 @@ context,
 '(?<=set @opt_context=\')([\n\r].*)*(?=\'\;#opt_context_ends)')
 from information_schema.optimizer_context);
 set @records=
-(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 select *from json_table(@records,
-'$[*]' columns(num_of_records text path '$')) as jt;
-num_of_records
+'$[*]' columns(file_stat_records text path '$')) as jt;
+file_stat_records
 30
 20
 set @file_stat_records=
@@ -225,10 +225,10 @@ context,
 '(?<=set @opt_context=\')([\n\r].*)*(?=\'\;#opt_context_ends)')
 from information_schema.optimizer_context);
 set @records=
-(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 select *from json_table(@records,
-'$[*]' columns(num_of_records text path '$')) as jt;
-num_of_records
+'$[*]' columns(file_stat_records text path '$')) as jt;
+file_stat_records
 20
 set @file_stat_records=
 (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
@@ -268,10 +268,10 @@ context,
 '(?<=set @opt_context=\')([\n\r].*)*(?=\'\;#opt_context_ends)')
 from information_schema.optimizer_context);
 set @records=
-(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 select *from json_table(@records,
-'$[*]' columns(num_of_records text path '$')) as jt;
-num_of_records
+'$[*]' columns(file_stat_records text path '$')) as jt;
+file_stat_records
 30
 20
 set @file_stat_records=
@@ -323,10 +323,10 @@ context,
 '(?<=set @opt_context=\')([\n\r].*)*(?=\'\;#opt_context_ends)')
 from information_schema.optimizer_context);
 set @records=
-(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 select *from json_table(@records,
-'$[*]' columns(num_of_records text path '$')) as jt;
-num_of_records
+'$[*]' columns(file_stat_records text path '$')) as jt;
+file_stat_records
 50
 set @file_stat_records=
 (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
@@ -371,10 +371,10 @@ context,
 '(?<=set @opt_context=\')([\n\r].*)*(?=\'\;#opt_context_ends)')
 from information_schema.optimizer_context);
 set @records=
-(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 select *from json_table(@records,
-'$[*]' columns(num_of_records text path '$')) as jt;
-num_of_records
+'$[*]' columns(file_stat_records text path '$')) as jt;
+file_stat_records
 50
 set @file_stat_records=
 (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
@@ -425,10 +425,10 @@ context,
 '(?<=set @opt_context=\')([\n\r].*)*(?=\'\;#opt_context_ends)')
 from information_schema.optimizer_context);
 set @records=
-(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 select *from json_table(@records,
-'$[*]' columns(num_of_records text path '$')) as jt;
-num_of_records
+'$[*]' columns(file_stat_records text path '$')) as jt;
+file_stat_records
 set @file_stat_records=
 (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 select *from json_table(@file_stat_records,
@@ -464,10 +464,10 @@ context,
 '(?<=set @opt_context=\')([\n\r].*)*(?=\'\;#opt_context_ends)')
 from information_schema.optimizer_context);
 set @records=
-(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.num_of_records')));
+(select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
 select *from json_table(@records,
-'$[*]' columns(num_of_records text path '$')) as jt;
-num_of_records
+'$[*]' columns(file_stat_records text path '$')) as jt;
+file_stat_records
 50
 set @file_stat_records=
 (select JSON_DETAILED(JSON_EXTRACT(@opt_context, '$**.file_stat_records')));
diff --git a/sql/opt_context_store_replay.cc b/sql/opt_context_store_replay.cc
index ec0a01944d600..b1eb90929dded 100644
--- a/sql/opt_context_store_replay.cc
+++ b/sql/opt_context_store_replay.cc
@@ -55,7 +55,7 @@ using namespace json_reader;
       "list_contexts": [
         {
           "name": "table_name",
-          "num_of_records": n,
+          "file_stat_records" : n
           "file_stat_records": n,
           "read_cost_io": n,
           "read_cost_cpu": n,
@@ -349,7 +349,6 @@ static void dump_table_stats(THD *thd, TABLE_LIST *tbl, uchar *tbl_name,
   ha_rows records= table->stat_records();
   IO_AND_CPU_COST cost= table->file->ha_scan_time(records);
   ctx_wrapper.add("name", (char *) tbl_name, tbl_name_len);
-  ctx_wrapper.add("num_of_records", records);
   ctx_wrapper.add("file_stat_records", table->file->stats.records);
   ctx_wrapper.add("read_cost_io", cost.io);
   ctx_wrapper.add("read_cost_cpu", cost.cpu);
@@ -976,9 +975,10 @@ class Saved_Table_stats : public Sql_alloc
 {
 public:
   TABLE *table;
-  ha_rows original_rows; // this is table->used_stat_records
-  /* saved table->file->stats.records */ 
-  ha_rows original_file_stats_records;
+  /*
+    We do not restore table->file->stats.records, they are read from the
+    storage engine for every query anyway.
+  */
   List<Saved_Index_stats> saved_indexstats_list;
 };
 
@@ -1214,9 +1214,6 @@ static int parse_table_context(THD *thd, json_engine_t *je, String *err_buf,
 
   Read_named_member array[]= {
       {"name", Read_string(thd, &table_ctx->name), false},
-      {"num_of_records",
-       Read_non_neg_integer<ha_rows, ULONGLONG_MAX>(&table_ctx->total_rows),
-       false},
       {"file_stat_records",
        Read_non_neg_integer<ha_rows, ULONGLONG_MAX>(&table_ctx->file_stat_records),
        false},
@@ -1646,9 +1643,12 @@ bool Optimizer_context_replay::infuse_index_read_cost(const TABLE *tbl,
   return true;
 }
 
+
 /*
   @brief
-    Save the current stats of the table and its associated table.
+    Infuse saved table statistics for a given table.
+    Current table statistics are saved away to be restored later.
+    #records is not handled by this function, see infuse_table_rows().
 */
 void Optimizer_context_replay::infuse_table_stats(TABLE *table)
 {
@@ -1661,66 +1661,61 @@ void Optimizer_context_replay::infuse_table_stats(TABLE *table)
     return; // OOM
 
   saved_ts->table= table;
-  saved_ts->original_rows= table->used_stat_records;
-  saved_ts->original_file_stats_records= table->file->stats.records;
 
   if (saved_table_stats.push_back(saved_ts))
     return;
 
-  if (!infuse_table_rows(table))
+  KEY *key_info, *key_info_end;
+  for (key_info= table->key_info, key_info_end= key_info + table->s->keys;
+       key_info < key_info_end; key_info++)
   {
-    KEY *key_info, *key_info_end;
-    for (key_info= table->key_info, key_info_end= key_info + table->s->keys;
-         key_info < key_info_end; key_info++)
-    {
-      List<ha_rows> *index_freq_list=
-          get_index_rec_per_key_list(table, key_info->name.str);
+    List<ha_rows> *index_freq_list=
+        get_index_rec_per_key_list(table, key_info->name.str);
 
-      if (index_freq_list && !index_freq_list->is_empty())
-      {
-        Saved_Index_stats *saved_is= new Saved_Index_stats();
+    if (!index_freq_list || index_freq_list->is_empty())
+      continue;
 
-        if (unlikely(!saved_is))
-          return; // OOM
+    Saved_Index_stats *saved_is= new Saved_Index_stats();
 
-        uint i= 0;
-        uint num_key_parts= key_info->user_defined_key_parts;
-        Index_statistics *original_read_stats= key_info->read_stats;
-        bool original_is_statistics_from_stat_tables=
-            key_info->is_statistics_from_stat_tables;
-        Index_statistics *new_read_stats= new Index_statistics();
+    if (unlikely(!saved_is))
+      return; // OOM
 
-        if (unlikely(!new_read_stats))
-          return; // OOM
+    uint i= 0;
+    uint num_key_parts= key_info->user_defined_key_parts;
+    Index_statistics *original_read_stats= key_info->read_stats;
+    bool original_is_statistics_from_stat_tables=
+        key_info->is_statistics_from_stat_tables;
+    Index_statistics *new_read_stats= new Index_statistics();
 
-        ulonglong *frequencies=
-            (ulonglong *) thd->alloc(sizeof(ulonglong) * num_key_parts);
+    if (unlikely(!new_read_stats))
+      return; // OOM
 
-        if (unlikely(!frequencies))
-          return; // OOM
+    ulonglong *frequencies=
+        (ulonglong *) thd->alloc(sizeof(ulonglong) * num_key_parts);
 
-        new_read_stats->init_avg_frequency(frequencies);
-        List_iterator li(*index_freq_list);
-        ha_rows *freq= li++;
-        key_info->read_stats= new_read_stats;
+    if (unlikely(!frequencies))
+      return; // OOM
 
-        while (freq && i < num_key_parts)
-        {
-          // Apparently this can be=0 for prefix indexes.
-          //DBUG_ASSERT(*freq > 0);
-          key_info->read_stats->set_avg_frequency(i, (double) *freq);
-          freq= li++;
-          i++;
-        }
+    new_read_stats->init_avg_frequency(frequencies);
+    List_iterator li(*index_freq_list);
+    ha_rows *freq= li++;
+    key_info->read_stats= new_read_stats;
 
-        key_info->is_statistics_from_stat_tables= true;
-        saved_is->key_info= key_info;
-        saved_is->original_is_statistics_from_stat_tables=
-            original_is_statistics_from_stat_tables;
-        saved_is->original_read_stats= original_read_stats;
-        saved_ts->saved_indexstats_list.push_back(saved_is);
-      }
+    while (freq && i < num_key_parts)
+    {
+      // Apparently this can be=0 for prefix indexes.
+      //DBUG_ASSERT(*freq > 0);
+      key_info->read_stats->set_avg_frequency(i, (double) *freq);
+      freq= li++;
+      i++;
     }
+
+    key_info->is_statistics_from_stat_tables= true;
+    saved_is->key_info= key_info;
+    saved_is->original_is_statistics_from_stat_tables=
+        original_is_statistics_from_stat_tables;
+    saved_is->original_read_stats= original_read_stats;
+    saved_ts->saved_indexstats_list.push_back(saved_is);
   }
 }
 
@@ -1780,9 +1775,6 @@ void Optimizer_context_replay::restore_modified_table_stats()
   List_iterator<Saved_Table_stats> table_li(saved_table_stats);
   while (Saved_Table_stats *saved_ts= table_li++)
   {
-    saved_ts->table->used_stat_records= saved_ts->original_rows;
-    saved_ts->table->file->stats.records= saved_ts->original_file_stats_records;
-
     List_iterator<Saved_Index_stats> index_li(saved_ts->saved_indexstats_list);
     while (Saved_Index_stats *saved_is= index_li++)
     {
@@ -1890,7 +1882,6 @@ void Optimizer_context_replay::dbug_print_read_stats()
     DBUG_PRINT("info", ("New Table Context"));
     DBUG_PRINT("info", ("-----------------"));
     DBUG_PRINT("info", ("name: %s", tbl_ctx->name));
-    DBUG_PRINT("info", ("num_of_records: %llx", tbl_ctx->total_rows));
     DBUG_PRINT("info",
                ("file_stat_records: %llx", tbl_ctx->file_stat_records));
 
@@ -1994,7 +1985,7 @@ bool Optimizer_context_replay::infuse_table_rows(TABLE *tbl)
   if (table_context_for_replay *tbl_ctx=
           find_table_context(tbl_name.c_ptr_safe()))
   {
-    tbl->used_stat_records= tbl_ctx->total_rows;
+    // Only infuse this one. table->used_stat_records are set by te SQL layer.
     tbl->file->stats.records= tbl_ctx->file_stat_records;
     return false;
   }
diff --git a/sql/opt_context_store_replay.h b/sql/opt_context_store_replay.h
index 8700e7e4c2b81..a7da98eaa25bd 100644
--- a/sql/opt_context_store_replay.h
+++ b/sql/opt_context_store_replay.h
@@ -110,6 +110,7 @@ class Optimizer_context_replay
 public:
   Optimizer_context_replay(THD *thd);
 
+  bool infuse_table_rows(TABLE *tbl);
   /* Save table's statistics and replace it with data from the context.  */
   void infuse_table_stats(TABLE *table);
   /* Restore the saved statistics back (to be done at query end) */
@@ -149,7 +150,6 @@ class Optimizer_context_replay
                                             const char *idx_name);
   void store_range_contexts(const TABLE *tbl, const char *idx_name,
                             List<Multi_range_read_const_call_record> *list);
-  bool infuse_table_rows(TABLE *tbl);
   table_context_for_replay *find_table_context(const char *name);
 };
 
diff --git a/sql/sql_statistics.cc b/sql/sql_statistics.cc
index 981c772d83925..a0088b5ae3779 100644
--- a/sql/sql_statistics.cc
+++ b/sql/sql_statistics.cc
@@ -4131,6 +4131,12 @@ void set_statistics_for_table(THD *thd, TABLE *table)
   TABLE_STATISTICS_CB *stats_cb= table->s->stats_cb;
   Table_statistics *read_stats= stats_cb ? stats_cb->table_stats : 0;
 
+  /*
+    Infuse the table->file->stats.records.
+    We will set table->used_stat_records right below.
+  */
+  if (thd->opt_ctx_replay)
+    thd->opt_ctx_replay->infuse_table_rows(table);
   /*
     The MAX below is to ensure that we don't return 0 rows for a table if it
     not guaranteed to be empty.
@@ -4188,6 +4194,10 @@ void set_statistics_for_table(THD *thd, TABLE *table)
       }
     }
   }
+  /*
+    TODO: infuse_table_rows() call above is done before the EITS-based
+    adjustments. Should this be moved up, too?
+  */
   if (thd->opt_ctx_replay)
     thd->opt_ctx_replay->infuse_table_stats(table);
 }

From 17f4dd83a9d214860f6581287aeb61275b67e0f4 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Sun, 26 Apr 2026 16:41:24 +0300
Subject: [PATCH 34/50] More --disable_replay for queries where we don't
 support it.

---
 mysql-test/main/derived_cond_pushdown.test    | 4 ++++
 mysql-test/main/opt_context_replay_basic.test | 2 +-
 mysql-test/main/subselect4.test               | 1 +
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/mysql-test/main/derived_cond_pushdown.test b/mysql-test/main/derived_cond_pushdown.test
index 70d5582e62c5a..102041f7ba8fd 100644
--- a/mysql-test/main/derived_cond_pushdown.test
+++ b/mysql-test/main/derived_cond_pushdown.test
@@ -2410,10 +2410,12 @@ select col2, col1 from v1
 union all
 select col2, col1 from v2;
 
+--disable_replay next_query Don't support SPs
 explain select * from v3 where col1=123;
 
 --echo # This must use ref accesses for reading table t1, not full scans:
 --source include/explain-no-costs.inc
+--disable_replay next_query Don't support SPs
 explain format=json
 select * from v3 where col1=123 and col2=321;
 
@@ -2438,6 +2440,7 @@ select a, f1(a), sum(b) from t1 group by a, f1(a);
 --echo #   "a2>123" will be pushed into HAVING (as it refers to an SP call which
 --echo #                                       prevents pushing it to the WHERE)
 --source include/explain-no-costs.inc
+--disable_replay next_query Don't support SPs
 explain format=json
 select * from v2 where (s+1) > 10 AND a > 1 and a2>123;
 
@@ -2451,6 +2454,7 @@ insert into t4 select a,a,a from t1;
 --echo #  "attached_condition": "t1.a + 1 > 10",
 --echo #  "having_condition": "`f1(a)` > 1 and `sum(b)` > 123",
 --source include/explain-no-costs.inc
+--disable_replay next_query Don't support SPs
 explain format=json
 select *
 from t4
diff --git a/mysql-test/main/opt_context_replay_basic.test b/mysql-test/main/opt_context_replay_basic.test
index d14017d17824f..f23d30797e92d 100644
--- a/mysql-test/main/opt_context_replay_basic.test
+++ b/mysql-test/main/opt_context_replay_basic.test
@@ -4,7 +4,7 @@
 --echo #enable optimizer_record_context
 set optimizer_record_context=ON;
 
---disable_replay testfile Don't replay a replay test
+--disable_replay testfile Dont replay a replay test
 
 create database db1;
 use db1;
diff --git a/mysql-test/main/subselect4.test b/mysql-test/main/subselect4.test
index a0fece967ca3e..668823a5a1970 100644
--- a/mysql-test/main/subselect4.test
+++ b/mysql-test/main/subselect4.test
@@ -2657,6 +2657,7 @@ create table t3 as select * from t1;
 analyze table t1,t2,t3;
 select @@expensive_subquery_limit < 200 as DEFAULTS_ARE_SUITABLE;
 flush status;
+--disable_replay testfile Need to preserve counter
 explain select * from t1 where a<3 or (select max(a) from t2) in (select b from t3);
 --echo # Must show 0. If this shows 200, this means subquery was executed and you have a bug:
 show status like 'Handler_read_rnd_next%';

From a27a8cfda287c08a861e297da41f6384dccf9ab1 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Sun, 26 Apr 2026 17:51:44 +0300
Subject: [PATCH 35/50] MDEV-39409: Context replay doesn't handle MIN/MAX
 optimization

Handle it by saving the MIN/MAX rows into Optimizer Context.
Like we do it for const tables.
---
 .../main/opt_context_replay_basic.result      | 20 ++++++++++++++
 mysql-test/main/opt_context_replay_basic.test | 26 +++++++++++++++++++
 sql/opt_context_store_replay.cc               |  4 +--
 sql/opt_context_store_replay.h                | 12 ++++++++-
 sql/opt_sum.cc                                |  7 +++++
 5 files changed, 66 insertions(+), 3 deletions(-)

diff --git a/mysql-test/main/opt_context_replay_basic.result b/mysql-test/main/opt_context_replay_basic.result
index fa2f610832add..974135524abd3 100644
--- a/mysql-test/main/opt_context_replay_basic.result
+++ b/mysql-test/main/opt_context_replay_basic.result
@@ -249,6 +249,26 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
 select context into dumpfile "../../tmp/dump1.sql"
 from information_schema.optimizer_context;
+set optimizer_record_context=OFF;
 drop table t1;
 drop table t1;
+#
+# MDEV-39409: Context replay doesnt handle MIN/MAX optimization
+#
+CREATE TABLE t1 (a int PRIMARY KEY, b int);
+INSERT INTO t1 VALUES (2,20), (3,10), (1,10), (0,30), (5,10);
+set optimizer_record_context=1;
+EXPLAIN SELECT MAX(a) FROM t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
+select context into dumpfile "../../tmp/dump1.sql"
+from information_schema.optimizer_context;
+set optimizer_record_context=0;
+drop table t1;
+set optimizer_replay_context='opt_context';
+# Same query as above, must have same explain:
+EXPLAIN SELECT MAX(a) FROM t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
+drop table t1;
 drop database db1;
diff --git a/mysql-test/main/opt_context_replay_basic.test b/mysql-test/main/opt_context_replay_basic.test
index f23d30797e92d..dcf85929c337b 100644
--- a/mysql-test/main/opt_context_replay_basic.test
+++ b/mysql-test/main/opt_context_replay_basic.test
@@ -83,6 +83,7 @@ EXPLAIN SELECT * FROM t1 WHERE a IN
   ((SELECT MAX(a) FROM t1), (SELECT MAX(a) FROM t1));
 select context into dumpfile "../../tmp/dump1.sql"
 from information_schema.optimizer_context;
+set optimizer_record_context=OFF;
 drop table t1;
 
 --disable_query_log
@@ -91,6 +92,31 @@ drop table t1;
 --enable_query_log
 --enable_result_log
 
+--remove_file "$MYSQLTEST_VARDIR/tmp/dump1.sql"
+drop table t1;
+
+--echo #
+--echo # MDEV-39409: Context replay doesnt handle MIN/MAX optimization
+--echo #
+CREATE TABLE t1 (a int PRIMARY KEY, b int);
+INSERT INTO t1 VALUES (2,20), (3,10), (1,10), (0,30), (5,10);
+
+set optimizer_record_context=1;
+EXPLAIN SELECT MAX(a) FROM t1;
+select context into dumpfile "../../tmp/dump1.sql"
+from information_schema.optimizer_context;
+set optimizer_record_context=0;
+drop table t1;
+--disable_query_log
+--disable_result_log
+--source "$MYSQLTEST_VARDIR/tmp/dump1.sql"
+--enable_query_log
+--enable_result_log
+set optimizer_replay_context='opt_context';
+--echo # Same query as above, must have same explain:
+EXPLAIN SELECT MAX(a) FROM t1;
+
+--remove_file "$MYSQLTEST_VARDIR/tmp/dump1.sql"
 drop table t1;
 
 drop database db1;
diff --git a/sql/opt_context_store_replay.cc b/sql/opt_context_store_replay.cc
index b1eb90929dded..9f47de3889ba1 100644
--- a/sql/opt_context_store_replay.cc
+++ b/sql/opt_context_store_replay.cc
@@ -883,12 +883,12 @@ void Optimizer_context_recorder::record_records_in_range(
   table_ctx->rir_list.push_back(rec_in_range_ctx, mem_root);
 }
 
-void Optimizer_context_recorder::record_const_table_row(TABLE *tbl)
+void Optimizer_context_recorder::record_table_row(TABLE *tbl, int row_index)
 {
   StringBuffer<512> output(&my_charset_utf8mb4_bin);
   output.append(STRING_WITH_LEN("REPLACE INTO "));
   append_full_table_name(tbl->pos_in_table_list, &output);
-  format_and_store_row(tbl, tbl->record[1], true, " VALUES ", false, output);
+  format_and_store_row(tbl, tbl->record[row_index], true, " VALUES ", false, output);
   table_context_for_store *table_ctx=
       get_table_context(tbl->pos_in_table_list);
 
diff --git a/sql/opt_context_store_replay.h b/sql/opt_context_store_replay.h
index a7da98eaa25bd..52e1360c31436 100644
--- a/sql/opt_context_store_replay.h
+++ b/sql/opt_context_store_replay.h
@@ -62,12 +62,22 @@ class Optimizer_context_recorder
                                const KEY_PART_INFO *key_part, uint keynr,
                                const key_range *min_range,
                                const key_range *max_range, ha_rows records);
-  void record_const_table_row(TABLE *tbl);
+  void record_const_table_row(TABLE *tbl)
+  {
+    /* use table->record[1] */
+    record_table_row(tbl, 1);
+  }
+  void record_current_table_row(TABLE *tbl)
+  {
+    /* use table->record[0] */
+    record_table_row(tbl, 0);
+  }
 
   bool has_records();
   table_context_for_store *search(uchar *tbl_name, size_t tbl_name_len);
 
 private:
+  void record_table_row(TABLE *tbl, int row_index);
   MEM_ROOT *mem_root;
   /*
     Hash table mapping "dbname.table_name" -> pointer to
diff --git a/sql/opt_sum.cc b/sql/opt_sum.cc
index 6d5bf8c6f487f..9ab9dcfaabe09 100644
--- a/sql/opt_sum.cc
+++ b/sql/opt_sum.cc
@@ -52,6 +52,7 @@
 #include "sql_priv.h"
 #include "key.h"                                // key_cmp_if_same
 #include "sql_select.h"
+#include "opt_context_store_replay.h"
 
 static bool find_key_for_maxmin(bool max_fl, TABLE_REF *ref, Field* field,
                                 COND *cond, uint *range_fl,
@@ -434,6 +435,12 @@ int opt_sum_query(THD *thd,
               reckey_in_range(is_max, &ref, item_field->field,
                               conds, range_fl, prefix_len))
 	    error= HA_ERR_KEY_NOT_FOUND;
+
+          if (!error)
+          {
+            if (Optimizer_context_recorder *rec= thd->opt_ctx_recorder)
+              rec->record_current_table_row(table);
+          }
           if (!table->const_table)
           {
             table->file->ha_end_keyread();

From 8b325e8cba8b11a5afd3ba8471155e9e354f0522 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Sun, 26 Apr 2026 19:08:52 +0300
Subject: [PATCH 36/50] MDEV-39447: Context Replay: "Field doesn't have default
 value" error

Instead of REPLACE INTO, use
SET STATEMENT sql_mode={remove STRICT_...TABLES} REPLACE INTO.
---
 mysql-test/main/opt_context_store_ddls.result  |  1 +
 mysql-test/main/opt_context_store_stats.result |  1 +
 sql/opt_context_store_replay.cc                | 11 +++++++++++
 3 files changed, 13 insertions(+)

diff --git a/mysql-test/main/opt_context_store_ddls.result b/mysql-test/main/opt_context_store_ddls.result
index 9eaaf82d0dba7..ebc2ead308b29 100644
--- a/mysql-test/main/opt_context_store_ddls.result
+++ b/mysql-test/main/opt_context_store_ddls.result
@@ -515,6 +515,7 @@ CREATE TABLE `t2` (
   PRIMARY KEY (`a`)
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci;
 
+SET STATEMENT sql_mode=REPLACE(REPLACE(@@sql_mode,'STRICT_ALL_TABLES',''),'STRICT_TRANS_TABLES','') FOR
 REPLACE INTO db1.t2(a, b) VALUES (1, 1);
 
 DROP TABLE IF EXISTS db1.t1;
diff --git a/mysql-test/main/opt_context_store_stats.result b/mysql-test/main/opt_context_store_stats.result
index d09e53620358b..e1db299dadf42 100644
--- a/mysql-test/main/opt_context_store_stats.result
+++ b/mysql-test/main/opt_context_store_stats.result
@@ -534,6 +534,7 @@ select @const_table_inserts;
 @const_table_inserts
 REPLACE INTO db1.t1(a, b) VALUES (5, 0);
 
+SET STATEMENT sql_mode=REPLACE(REPLACE(@@sql_mode,'STRICT_ALL_TABLES',''),'STRICT_TRANS_TABLES','') FOR
 REPLACE INTO db1.t1(a, b) VALUES (4, 4);
 
 REPLACE INTO mysql.table_stats VALUES ('db1', 't1', 20);
diff --git a/sql/opt_context_store_replay.cc b/sql/opt_context_store_replay.cc
index 9f47de3889ba1..252174eea2c04 100644
--- a/sql/opt_context_store_replay.cc
+++ b/sql/opt_context_store_replay.cc
@@ -886,6 +886,17 @@ void Optimizer_context_recorder::record_records_in_range(
 void Optimizer_context_recorder::record_table_row(TABLE *tbl, int row_index)
 {
   StringBuffer<512> output(&my_charset_utf8mb4_bin);
+
+  /*
+    The table could have fields that do not have a default value
+    but are not in the table->read_set.
+    The record doesn't have values for those.
+    Use a relaxed sql_mode setting so that REPLACE INTO doesn't fail.
+  */
+  output.append(
+    STRING_WITH_LEN("SET STATEMENT sql_mode="
+                    "REPLACE(REPLACE(@@sql_mode,'STRICT_ALL_TABLES',''),"
+                    "'STRICT_TRANS_TABLES','') FOR\n"));
   output.append(STRING_WITH_LEN("REPLACE INTO "));
   append_full_table_name(tbl->pos_in_table_list, &output);
   format_and_store_row(tbl, tbl->record[row_index], true, " VALUES ", false, output);

From 4b919381f085524622d757d93c3add4884e2e459 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Sun, 26 Apr 2026 21:53:21 +0300
Subject: [PATCH 37/50] [No MDEV#] Fix charset/collation mismatch errors

Make Optimizer Context include
  SET character_set_client=...;
  SET NAMES ... COLLATE ...;
---
 mysql-test/main/opt_context_replay_basic.result |  2 ++
 sql/opt_context_store_replay.cc                 | 11 +++++++++++
 2 files changed, 13 insertions(+)

diff --git a/mysql-test/main/opt_context_replay_basic.result b/mysql-test/main/opt_context_replay_basic.result
index 974135524abd3..34f9b4d6d2271 100644
--- a/mysql-test/main/opt_context_replay_basic.result
+++ b/mysql-test/main/opt_context_replay_basic.result
@@ -158,6 +158,8 @@ set @opt_context='
 }
 ';
 set optimizer_replay_context='opt_context';
+SET character_set_client=latin1;
+SET NAMES latin1 COLLATE latin1_swedish_ci;
 select count(*) from t1;
 count(*)
 0
diff --git a/sql/opt_context_store_replay.cc b/sql/opt_context_store_replay.cc
index 252174eea2c04..a51d36c477669 100644
--- a/sql/opt_context_store_replay.cc
+++ b/sql/opt_context_store_replay.cc
@@ -691,6 +691,17 @@ bool store_optimizer_context(THD *thd)
     sql_script.append(STRING_WITH_LEN("\n\';#opt_context_ends\n\n"));
     sql_script.append(SET_REPLAY_CONTEXT_VAR, strlen(SET_REPLAY_CONTEXT_VAR));
     sql_script.append(STRING_WITH_LEN(";\n\n"));
+
+    sql_script.append(STRING_WITH_LEN("SET character_set_client="));
+    sql_script.append(thd->variables.character_set_client->cs_name);
+    sql_script.append(STRING_WITH_LEN(";\n"));
+
+    sql_script.append(STRING_WITH_LEN("SET NAMES "));
+    sql_script.append(thd->variables.collation_connection->cs_name);
+    sql_script.append(STRING_WITH_LEN(" COLLATE "));
+    sql_script.append(thd->variables.collation_connection->coll_name);
+    sql_script.append(STRING_WITH_LEN(";\n"));
+
     sql_script.append(thd->query(), thd->query_length());
     sql_script.append(STRING_WITH_LEN(";\n\n"));
     sql_script.append(STRING_WITH_LEN("set optimizer_replay_context='';\n\n"));

From e10630c2d4a294b6344ba67d043e35c066ecc8f1 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Mon, 27 Apr 2026 13:25:22 +0300
Subject: [PATCH 38/50] Add more --disable_replay next_query Don't support SPs

---
 mysql-test/main/cte_recursive.test        | 2 ++
 mysql-test/main/having.test               | 1 +
 mysql-test/main/having_cond_pushdown.test | 2 ++
 mysql-test/main/select.test               | 1 +
 mysql-test/main/subselect_sj_mat.test     | 2 ++
 5 files changed, 8 insertions(+)

diff --git a/mysql-test/main/cte_recursive.test b/mysql-test/main/cte_recursive.test
index 30f94667b2d02..768eb06fae5a6 100644
--- a/mysql-test/main/cte_recursive.test
+++ b/mysql-test/main/cte_recursive.test
@@ -2640,7 +2640,9 @@ where (dt.a1) in (with recursive cte as (select a2 from t2 where a2='2'
 select a2 from cte);
 
 eval $q;
+--disable_replay next_query Dont support SPs
 eval explain $q;
+--disable_replay next_query Dont support SPs
 --source include/analyze-format.inc
 eval analyze format=json $q;
 
diff --git a/mysql-test/main/having.test b/mysql-test/main/having.test
index 98b5ed851fbf7..32fdbed5cc0f2 100644
--- a/mysql-test/main/having.test
+++ b/mysql-test/main/having.test
@@ -898,6 +898,7 @@ CREATE TABLE t1 (t INT, u INT, KEY(t));
 INSERT INTO t1 VALUES(10, 10), (11, 11), (12, 12), (12, 13),(14, 15), (15, 16),
                      (16, 17), (17, 17);
 ANALYZE TABLE t1;
+--disable_replay next_query Don't support SPs
 explain SELECT t, next_seq_value() r FROM t1 FORCE INDEX(t) GROUP BY t HAVING r = 1  ORDER BY t1.u;
 --disable_ps2_protocol
 SELECT t, next_seq_value() r FROM t1 FORCE INDEX(t) GROUP BY t HAVING r = 1  ORDER BY t1.u;
diff --git a/mysql-test/main/having_cond_pushdown.test b/mysql-test/main/having_cond_pushdown.test
index faf6e51192163..25da708bf00f5 100644
--- a/mysql-test/main/having_cond_pushdown.test
+++ b/mysql-test/main/having_cond_pushdown.test
@@ -255,6 +255,7 @@ GROUP BY t1.a
 HAVING (t1.a>1) AND (a=test.f1());
 eval $no_pushdown $query;
 eval $query;
+--disable_replay next_query Dont support SPs
 eval explain $query;
 --source include/explain-no-costs.inc
 eval explain format=json $query;
@@ -264,6 +265,7 @@ FROM t1
 WHERE (t1.a>1)
 GROUP BY t1.a
 HAVING (a=test.f1());
+--disable_replay next_query Dont support SPs
 --source include/explain-no-costs.inc
 eval $no_pushdown explain format=json $query;
 
diff --git a/mysql-test/main/select.test b/mysql-test/main/select.test
index ca248b26b9109..2013bfa3516f1 100644
--- a/mysql-test/main/select.test
+++ b/mysql-test/main/select.test
@@ -4144,6 +4144,7 @@ SET @cnt := 0;
 SELECT * FROM t1 WHERE a = f1();
 --enable_ps2_protocol
 SELECT @cnt;
+--disable_replay next_query Don't support SPs
 EXPLAIN EXTENDED SELECT * FROM t1 WHERE a = f1();
 DROP TABLE t1, t2;
 DROP FUNCTION f1;
diff --git a/mysql-test/main/subselect_sj_mat.test b/mysql-test/main/subselect_sj_mat.test
index 3dcef80b9ffe8..a4fa04fffd099 100644
--- a/mysql-test/main/subselect_sj_mat.test
+++ b/mysql-test/main/subselect_sj_mat.test
@@ -2323,6 +2323,7 @@ select * from t1
     where f2(t1.id, '1980-01-01') in (select id from t2 where x=1);
 
 eval $q2;
+--disable_replay next_query Don't support SPs
 eval explain extended $q2;
 
 let $q3=
@@ -2332,6 +2333,7 @@ select t1.*, t4.*,
     where f2(t1.id, '1980-01-01') in (select id from t2 where x=1);
 
 eval $q3;
+--disable_replay next_query Don't support SPs
 eval explain extended $q3;
 
 drop function f1;

From fe133655f5aadd6fc86005a815eaf744800e49ca Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Mon, 27 Apr 2026 13:28:56 +0300
Subject: [PATCH 39/50] Add --disable_replay next_query Will try to create
 table for sequence engine

---
 mysql-test/main/user_var.test | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mysql-test/main/user_var.test b/mysql-test/main/user_var.test
index 3141490c7a17c..add31bb693f8a 100644
--- a/mysql-test/main/user_var.test
+++ b/mysql-test/main/user_var.test
@@ -519,6 +519,7 @@ eval select $tmp < $tmp2;
 #
 # MDEV-13897 SELECT @a := MAX(col) FROM t requires full index scan
 #
+--disable_replay next_query Will try to create table for sequence engine
 explain select @a:=max(seq) from seq_1_to_1000000;
 
 # End of 10.1 tests

From e6427ad09cfadbc79ddcf37183eb1ea6a6a21951 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Mon, 27 Apr 2026 15:18:00 +0300
Subject: [PATCH 40/50] Test result update.

---
 mysql-test/main/opt_context_load_stats_basic.result | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mysql-test/main/opt_context_load_stats_basic.result b/mysql-test/main/opt_context_load_stats_basic.result
index b07657d877794..054dc827ed7aa 100644
--- a/mysql-test/main/opt_context_load_stats_basic.result
+++ b/mysql-test/main/opt_context_load_stats_basic.result
@@ -359,7 +359,7 @@ set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].file_stat
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "file_stat_records" element not present at offset 1402.
+Warning	4253	Failed to parse saved optimizer context: "file_stat_records" element not present at offset 1380.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].indexes[0].index_name');
 select * from t1 where a > 10;
 a	b

From e3b0ca29389e5b68ebd7a48df10afeb996ce2976 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 13 Mar 2026 15:09:43 +0200
Subject: [PATCH 41/50] Cherry-pick lost commit: Improve comments and
 readability.

---
 sql/opt_context_store_replay.cc |  7 ++-----
 sql/opt_context_store_replay.h  | 21 ++++++++++++++-------
 2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/sql/opt_context_store_replay.cc b/sql/opt_context_store_replay.cc
index a51d36c477669..3fafc70824631 100644
--- a/sql/opt_context_store_replay.cc
+++ b/sql/opt_context_store_replay.cc
@@ -145,7 +145,7 @@ class records_in_range_call_record : public Sql_alloc
 class table_context_for_store : public Sql_alloc
 {
 public:
-  /* full name of the table or view i.e db_name.{table|view}_name */
+  /* Full name of the table or view i.e db_name.{table|view}_name */
   char *name;
   size_t name_len;
   List<Multi_range_read_const_call_record> mrr_list;
@@ -956,10 +956,7 @@ class index_context_for_replay : public Sql_alloc
 class table_context_for_replay : public Sql_alloc
 {
 public:
-  /*
-     full name of the table or view
-     i.e db_name.[table/view]_name
-  */
+  /* Full name of the table or view i.e db_name.{table|view}_name */
   char *name;
   ha_rows total_rows;
   ha_rows file_stat_records;
diff --git a/sql/opt_context_store_replay.h b/sql/opt_context_store_replay.h
index 52e1360c31436..c73dd56f5acf8 100644
--- a/sql/opt_context_store_replay.h
+++ b/sql/opt_context_store_replay.h
@@ -108,13 +108,18 @@ class Saved_Table_stats;
 void init_optimizer_context_replay_if_needed(THD *thd);
 
 /*
-  This class stores the parsed optimizer context information
-  and then infuses read stats into the optimizer
+  Optimizer context that's loaded and can be used for replay.
 
-  Optimizer Context information that we've read from a JSON document.
+  - When this object is created, it will parse the context JSON document
+    from a user variable pointed by @@optimizer_replay_context.
 
-  The optimizer can use infuse_XXX() methods to get the saved values.
+  - The optimizer checks thd->opt_ctx_replay, if it is present, it will call
+
+       thd->opt_ctx_replay->infuse_XXX()
+
+    to get "infuse" the statistics records from the context.
 */
+
 class Optimizer_context_replay
 {
 public:
@@ -143,6 +148,8 @@ class Optimizer_context_replay
                                const key_range *max_range, ha_rows *records);
 
 private:
+  bool infuse_table_rows(const TABLE *tbl, ha_rows *rows);
+
   THD *thd;
   /*
     Statistics that tables had before we've replaced them with values from
@@ -153,14 +160,14 @@ class Optimizer_context_replay
   List<table_context_for_replay> ctx_list;
   bool parse();
   bool has_records();
-#ifndef DBUG_OFF
-  void dbug_print_read_stats();
-#endif
   List<ha_rows> *get_index_rec_per_key_list(const TABLE *tbl,
                                             const char *idx_name);
   void store_range_contexts(const TABLE *tbl, const char *idx_name,
                             List<Multi_range_read_const_call_record> *list);
   table_context_for_replay *find_table_context(const char *name);
+#ifndef DBUG_OFF
+  void dbug_print_read_stats();
+#endif
 };
 
 /*

From 5f9a4a812df67702ef9da3165f07abe49e027b28 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 13 Mar 2026 15:25:49 +0200
Subject: [PATCH 42/50] Cherry-pick lost commit: Rename dump_XXXX() functions
 and make them more readable.

---
 sql/opt_context_store_replay.cc | 99 +++++++++++++++++----------------
 1 file changed, 50 insertions(+), 49 deletions(-)

diff --git a/sql/opt_context_store_replay.cc b/sql/opt_context_store_replay.cc
index 3fafc70824631..ec365ded5db33 100644
--- a/sql/opt_context_store_replay.cc
+++ b/sql/opt_context_store_replay.cc
@@ -243,36 +243,37 @@ static bool is_base_table(const TABLE_LIST *tbl)
           tbl->table->s->tmp_table != SYSTEM_TMP_TABLE);
 }
 
-static void dump_range_stats(THD *thd, table_context_for_store *context,
-                             Json_writer *ctx_writer)
+static
+void dump_mrr_info_calls(List<Multi_range_read_const_call_record> *mrr_list,
+                         Json_writer *ctx_writer)
 {
   Json_writer_array list_ranges_wrapper(ctx_writer, "list_ranges");
-  List_iterator irc_li(context->mrr_list);
+  List_iterator irc_li(*mrr_list);
   while (Multi_range_read_const_call_record *irc= irc_li++)
   {
     Json_writer_object irc_wrapper(ctx_writer);
     irc_wrapper.add("index_name", irc->idx_name);
-    List_iterator rc_li(irc->range_list);
-    Json_writer_array ranges_wrapper(ctx_writer, "ranges");
-    while (const char *range_str= rc_li++)
+
     {
-      ranges_wrapper.add(range_str, strlen(range_str));
+      Json_writer_array ranges_wrapper(ctx_writer, "ranges");
+      List_iterator rc_li(irc->range_list);
+      while (const char *range_str= rc_li++)
+        ranges_wrapper.add(range_str, strlen(range_str));
     }
-    ranges_wrapper.end();
 
     irc_wrapper.add("num_rows", irc->rows);
     {
-      Json_writer_object cost_wrapper(ctx_writer, "cost");
-      cost_wrapper.add("avg_io_cost", irc->cost.avg_io_cost);
-      cost_wrapper.add("cpu_cost", irc->cost.cpu_cost);
-      cost_wrapper.add("comp_cost", irc->cost.comp_cost);
-      cost_wrapper.add("copy_cost", irc->cost.copy_cost);
-      cost_wrapper.add("limit_cost", irc->cost.limit_cost);
-      cost_wrapper.add("setup_cost", irc->cost.setup_cost);
-      cost_wrapper.add("index_cost_io", irc->cost.index_cost.io);
-      cost_wrapper.add("index_cost_cpu", irc->cost.index_cost.cpu);
-      cost_wrapper.add("row_cost_io", irc->cost.row_cost.io);
-      cost_wrapper.add("row_cost_cpu", irc->cost.row_cost.cpu);
+      Json_writer_object obj(ctx_writer, "cost");
+      obj.add("avg_io_cost", irc->cost.avg_io_cost);
+      obj.add("cpu_cost", irc->cost.cpu_cost);
+      obj.add("comp_cost", irc->cost.comp_cost);
+      obj.add("copy_cost", irc->cost.copy_cost);
+      obj.add("limit_cost", irc->cost.limit_cost);
+      obj.add("setup_cost", irc->cost.setup_cost);
+      obj.add("index_cost_io", irc->cost.index_cost.io);
+      obj.add("index_cost_cpu", irc->cost.index_cost.cpu);
+      obj.add("row_cost_io", irc->cost.row_cost.io);
+      obj.add("row_cost_cpu", irc->cost.row_cost.cpu);
     }
 
     irc_wrapper.add("max_index_blocks", irc->max_index_blocks);
@@ -280,46 +281,48 @@ static void dump_range_stats(THD *thd, table_context_for_store *context,
   }
 }
 
-static void dump_index_read_cost(THD *thd, table_context_for_store *context,
-                                 Json_writer *ctx_writer)
+static void dump_index_read_calls(List<cost_index_read_call_record> *irc_list,
+                                  Json_writer *ctx_writer)
 {
   Json_writer_array list_irc_wrapper(ctx_writer, "list_index_read_costs");
-  List_iterator irc_li(context->irc_list);
+  List_iterator irc_li(*irc_list);
 
   while (cost_index_read_call_record *irc= irc_li++)
   {
-    Json_writer_object irc_wrapper(ctx_writer);
-    irc_wrapper.add("key_number", irc->key);
-    irc_wrapper.add("num_records", irc->records);
-    irc_wrapper.add("eq_ref", irc->eq_ref ? 1 : 0);
-    irc_wrapper.add("index_cost_io", irc->cost.index_cost.io);
-    irc_wrapper.add("index_cost_cpu", irc->cost.index_cost.cpu);
-    irc_wrapper.add("row_cost_io", irc->cost.row_cost.io);
-    irc_wrapper.add("row_cost_cpu", irc->cost.row_cost.cpu);
-    irc_wrapper.add("max_index_blocks", irc->cost.max_index_blocks);
-    irc_wrapper.add("max_row_blocks", irc->cost.max_row_blocks);
-    irc_wrapper.add("copy_cost", irc->cost.copy_cost);
+    Json_writer_object obj(ctx_writer);
+    obj.add("key_number", irc->key);
+    obj.add("num_records", irc->records);
+    obj.add("eq_ref", irc->eq_ref ? 1 : 0);
+    obj.add("index_cost_io", irc->cost.index_cost.io);
+    obj.add("index_cost_cpu", irc->cost.index_cost.cpu);
+    obj.add("row_cost_io", irc->cost.row_cost.io);
+    obj.add("row_cost_cpu", irc->cost.row_cost.cpu);
+    obj.add("max_index_blocks", irc->cost.max_index_blocks);
+    obj.add("max_row_blocks", irc->cost.max_row_blocks);
+    obj.add("copy_cost", irc->cost.copy_cost);
   }
 }
 
-static void dump_records_in_range(THD *thd, table_context_for_store *context,
-                                  Json_writer *ctx_writer)
+static
+void dump_records_in_range_calls(List<records_in_range_call_record> *rir_list,
+                                 Json_writer *ctx_writer)
 {
   Json_writer_array list_irc_wrapper(ctx_writer, "list_records_in_range");
-  List_iterator rir_li(context->rir_list);
+  List_iterator rir_li(*rir_list);
 
   while (records_in_range_call_record *rir= rir_li++)
   {
-    Json_writer_object rir_wrapper(ctx_writer);
-    rir_wrapper.add("key_number", rir->keynr);
-    rir_wrapper.add("min_key", rir->min_key);
-    rir_wrapper.add("max_key", rir->max_key);
-    rir_wrapper.add("num_records", rir->records);
+    Json_writer_object obj(ctx_writer);
+    obj.add("key_number", rir->keynr);
+    obj.add("min_key", rir->min_key);
+    obj.add("max_key", rir->max_key);
+    obj.add("num_records", rir->records);
   }
 }
 
-static void dump_index_stats(THD *thd, uchar *tbl_name, size_t tbl_name_len,
-                             Json_writer *ctx_writer)
+static
+void dump_recorded_table_calls(THD *thd, uchar *tbl_name, size_t tbl_name_len,
+                               Json_writer *ctx_writer)
 {
   table_context_for_store *table_context=
       thd->opt_ctx_recorder->search(tbl_name, tbl_name_len);
@@ -327,9 +330,9 @@ static void dump_index_stats(THD *thd, uchar *tbl_name, size_t tbl_name_len,
   if (!table_context)
     return;
 
-  dump_range_stats(thd, table_context, ctx_writer);
-  dump_index_read_cost(thd, table_context, ctx_writer);
-  dump_records_in_range(thd, table_context, ctx_writer);
+  dump_mrr_info_calls(&table_context->mrr_list, ctx_writer);
+  dump_index_read_calls(&table_context->irc_list, ctx_writer);
+  dump_records_in_range_calls(&table_context->rir_list, ctx_writer);
 }
 
 /*
@@ -364,13 +367,11 @@ static void dump_table_stats(THD *thd, TABLE_LIST *tbl, uchar *tbl_name,
     index_wrapper.add("index_name", key->name);
     Json_writer_array rpk_wrapper(ctx_writer, "rec_per_key");
     for (uint i= 0; i < num_key_parts; i++)
-    {
       rpk_wrapper.add(key->actual_rec_per_key(i));
-    }
     rpk_wrapper.end();
   }
   indexes_wrapper.end();
-  dump_index_stats(thd, tbl_name, tbl_name_len, ctx_writer);
+  dump_recorded_table_calls(thd, tbl_name, tbl_name_len, ctx_writer);
 }
 
 static void create_view_def(THD *thd, TABLE_LIST *table, String *name,

From 037174e70d803fd77bb6d7cd397d2e121472b1bb Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 13 Mar 2026 15:37:12 +0200
Subject: [PATCH 43/50] Cherry-pick lost commit: Coding style renames:
 Saved_index_stats, Saved_table_stats

---
 sql/opt_context_store_replay.cc | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/sql/opt_context_store_replay.cc b/sql/opt_context_store_replay.cc
index ec365ded5db33..9d35e41d8c883 100644
--- a/sql/opt_context_store_replay.cc
+++ b/sql/opt_context_store_replay.cc
@@ -781,7 +781,10 @@ void Optimizer_context_recorder::record_multi_range_read_info_const(
     ha_rows max_index_blocks,
     ha_rows max_row_blocks)
 {
-  /* Do not record calls made by "Range checked for each record" */
+  /*
+    Do not record calls that are made at execution phase by "Range checked
+    for each record"
+  */
   if (current_thd->lex->explain->is_query_plan_ready())
     return;
 
@@ -809,12 +812,7 @@ void Optimizer_context_recorder::record_multi_range_read_info_const(
     range_ctx->range_list.push_back(range_str, mem_root);
   }
 
-  /*
-    Store the ranges of every index of the table into the
-    table context.
-  */
   table_context_for_store *table_ctx= get_table_context(tbl);
-
   if (unlikely(!table_ctx))
     return; // OOM
 
@@ -976,7 +974,7 @@ class table_context_for_replay : public Sql_alloc
   They are restored once the query that used replay json stats is done
   execution.
 */
-class Saved_Index_stats : public Sql_alloc
+class Saved_index_stats : public Sql_alloc
 {
 public:
   KEY *key_info;
@@ -991,7 +989,7 @@ class Saved_Index_stats : public Sql_alloc
   They are restored once the query that used replay json stats is done
   execution.
 */
-class Saved_Table_stats : public Sql_alloc
+class Saved_table_stats : public Sql_alloc
 {
 public:
   TABLE *table;
@@ -999,7 +997,7 @@ class Saved_Table_stats : public Sql_alloc
     We do not restore table->file->stats.records, they are read from the
     storage engine for every query anyway.
   */
-  List<Saved_Index_stats> saved_indexstats_list;
+  List<Saved_index_stats> saved_index_stats;
 };
 
 /*
@@ -1675,7 +1673,7 @@ void Optimizer_context_replay::infuse_table_stats(TABLE *table)
   if (!has_records() || !is_base_table(table->pos_in_table_list))
     return;
 
-  Saved_Table_stats *saved_ts= new Saved_Table_stats();
+  Saved_table_stats *saved_ts= new Saved_table_stats();
 
   if (unlikely(!saved_ts))
     return; // OOM
@@ -1735,7 +1733,7 @@ void Optimizer_context_replay::infuse_table_stats(TABLE *table)
     saved_is->original_is_statistics_from_stat_tables=
         original_is_statistics_from_stat_tables;
     saved_is->original_read_stats= original_read_stats;
-    saved_ts->saved_indexstats_list.push_back(saved_is);
+    saved_ts->saved_index_stats.push_back(saved_is);
   }
 }
 
@@ -1792,11 +1790,11 @@ bool Optimizer_context_replay::infuse_records_in_range(
 */
 void Optimizer_context_replay::restore_modified_table_stats()
 {
-  List_iterator<Saved_Table_stats> table_li(saved_table_stats);
-  while (Saved_Table_stats *saved_ts= table_li++)
+  List_iterator<Saved_table_stats> table_li(saved_table_stats);
+  while (Saved_table_stats *saved_ts= table_li++)
   {
-    List_iterator<Saved_Index_stats> index_li(saved_ts->saved_indexstats_list);
-    while (Saved_Index_stats *saved_is= index_li++)
+    List_iterator<Saved_index_stats> index_li(saved_ts->saved_index_stats);
+    while (Saved_index_stats *saved_is= index_li++)
     {
       KEY *key= saved_is->key_info;
       key->is_statistics_from_stat_tables=

From 6e1c732fa162837c79dbb3dde20c28ede9a0d91b Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 13 Mar 2026 15:56:09 +0200
Subject: [PATCH 44/50] Cherry-pick lost commit: Fixup to previous commit

---
 sql/opt_context_store_replay.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sql/opt_context_store_replay.h b/sql/opt_context_store_replay.h
index c73dd56f5acf8..916e56356d17f 100644
--- a/sql/opt_context_store_replay.h
+++ b/sql/opt_context_store_replay.h
@@ -103,7 +103,7 @@ bool store_optimizer_context(THD *thd);
 class table_context_for_replay;
 class index_context_for_replay;
 
-class Saved_Table_stats;
+class Saved_table_stats;
 
 void init_optimizer_context_replay_if_needed(THD *thd);
 
@@ -155,7 +155,7 @@ class Optimizer_context_replay
     Statistics that tables had before we've replaced them with values from
     the saved context. To be used to restore the original values.
   */
-  List<Saved_Table_stats> saved_table_stats;
+  List<Saved_table_stats> saved_table_stats;
 
   List<table_context_for_replay> ctx_list;
   bool parse();

From 0af4790be6bd5be8ce68c272b35c5c13baf0c786 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 13 Mar 2026 17:54:04 +0200
Subject: [PATCH 45/50] Cherry-pick lost commit: Fixup (2)

---
 sql/opt_context_store_replay.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sql/opt_context_store_replay.cc b/sql/opt_context_store_replay.cc
index 9d35e41d8c883..6f0d854334695 100644
--- a/sql/opt_context_store_replay.cc
+++ b/sql/opt_context_store_replay.cc
@@ -1693,7 +1693,7 @@ void Optimizer_context_replay::infuse_table_stats(TABLE *table)
     if (!index_freq_list || index_freq_list->is_empty())
       continue;
 
-    Saved_Index_stats *saved_is= new Saved_Index_stats();
+    Saved_index_stats *saved_is= new Saved_index_stats();
 
     if (unlikely(!saved_is))
       return; // OOM

From bf90ff4a5415fc5a2b4480284811dd0824e22ccb Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Fri, 13 Mar 2026 18:14:16 +0200
Subject: [PATCH 46/50] Cherry-pick lost commit: JSON parsing: rename classes
 to cleaner names

Read_container_value -> Read_array.
Read_list_of_context -> Read_array_into_list
---
 sql/opt_context_store_replay.cc | 59 +++++++++------------------------
 sql/sql_json_lib.h              | 33 ++++++++++++++++++
 2 files changed, 48 insertions(+), 44 deletions(-)

diff --git a/sql/opt_context_store_replay.cc b/sql/opt_context_store_replay.cc
index 6f0d854334695..fdc4aac35dce6 100644
--- a/sql/opt_context_store_replay.cc
+++ b/sql/opt_context_store_replay.cc
@@ -1000,41 +1000,7 @@ class Saved_table_stats : public Sql_alloc
   List<Saved_index_stats> saved_index_stats;
 };
 
-/*
-  Extends the Read_value interface to read a container of values,
-  for eg: array of numbers or strings, an object with several fields, etc...
-*/
-class Read_container_value : public Read_value
-{
-private:
-  int before_read(json_engine_t *je, const char *value_name, String *err_buf)
-  {
-    if (json_scan_next(je) || je->state != JST_ARRAY_START)
-    {
-      err_buf->append(STRING_WITH_LEN("error reading "));
-      err_buf->append(value_name, strlen(value_name));
-      err_buf->append(STRING_WITH_LEN(" value"));
-      return 1;
-    }
-    return 0;
-  }
-
-  int after_read(int rc) { return rc > 0; }
-
-public:
-  bool read_value(json_engine_t *je, const char *value_name,
-                  String *err_buf) override
-  {
-    int rc= before_read(je, value_name, err_buf);
-    if (rc <= 0)
-    {
-      rc= read_container(je, err_buf);
-    }
-    return after_read(rc);
-  }
-  virtual int read_container(json_engine_t *je, String *err_buf)= 0;
-};
-
+// psergey: Reads a JSON object
 class Read_range_cost_estimate : public Read_value
 {
   THD *thd;
@@ -1052,7 +1018,8 @@ class Read_range_cost_estimate : public Read_value
   }
 };
 
-class Read_list_of_ha_rows : public Read_container_value
+
+class Read_list_of_ha_rows : public Read_array
 {
   THD *thd;
   List<ha_rows> *list_values;
@@ -1089,14 +1056,18 @@ class Read_list_of_ha_rows : public Read_container_value
   }
 };
 
-template <typename T> class Read_list_of_context : public Read_container_value
+/*
+  Read an array of JSON objects representing object T. 
+  Create instances of T and collect them in a List<T> 
+*/
+template <typename T> class Read_array_into_list : public Read_array
 {
   THD *thd;
   List<T> *list_ctx;
   int (*parse_context_fn)(THD *, json_engine_t *, String *, T *);
 
 public:
-  Read_list_of_context(THD *thd_arg, List<T> *list_ctx_arg,
+  Read_array_into_list(THD *thd_arg, List<T> *list_ctx_arg,
                        int (*parse_context_fn_arg)(THD *, json_engine_t *,
                                                    String *, T *))
       : thd(thd_arg), list_ctx(list_ctx_arg),
@@ -1129,7 +1100,7 @@ template <typename T> class Read_list_of_context : public Read_container_value
   }
 };
 
-class Read_list_of_ranges : public Read_container_value
+class Read_list_of_ranges : public Read_array
 {
   THD *thd;
   List<char> *list_ranges;
@@ -1238,19 +1209,19 @@ static int parse_table_context(THD *thd, json_engine_t *je, String *err_buf,
       {"read_cost_io", Read_double(&table_ctx->read_cost_io), false},
       {"read_cost_cpu", Read_double(&table_ctx->read_cost_cpu), false},
       {"indexes",
-       Read_list_of_context<index_context_for_replay>(
+       Read_array_into_list<index_context_for_replay>(
            thd, &table_ctx->index_list, parse_index_context),
        true},
       {"list_ranges",
-       Read_list_of_context<Multi_range_read_const_call_record>(
+       Read_array_into_list<Multi_range_read_const_call_record>(
            thd, &table_ctx->ranges_list, parse_range_context),
        true},
       {"list_index_read_costs",
-       Read_list_of_context<cost_index_read_call_record>(
+       Read_array_into_list<cost_index_read_call_record>(
            thd, &table_ctx->irc_list, parse_index_read_cost_context),
        true},
       {"list_records_in_range",
-       Read_list_of_context<records_in_range_call_record>(
+       Read_array_into_list<records_in_range_call_record>(
            thd, &table_ctx->rir_list, parse_records_in_range_context),
        true},
       {NULL, Read_double(NULL), true}};
@@ -1830,7 +1801,7 @@ bool Optimizer_context_replay::parse()
   LEX_CSTRING varname= {var_name, strlen(var_name)};
 
   Read_named_member array[]= {{"list_contexts",
-                               Read_list_of_context<table_context_for_replay>(
+                               Read_array_into_list<table_context_for_replay>(
                                    thd, &ctx_list, parse_table_context),
                                false},
                               {NULL, Read_double(NULL), true}};
diff --git a/sql/sql_json_lib.h b/sql/sql_json_lib.h
index 2c8a7c1c2446a..c1dce502b3550 100644
--- a/sql/sql_json_lib.h
+++ b/sql/sql_json_lib.h
@@ -230,6 +230,39 @@ class Read_non_neg_integer : public Read_value
   }
 };
 
+/*
+  Extends the Read_value interface to read an array of elements.
+  Descendant classes implement read_container()
+  // TODO: make it read_array_elem ?
+*/
+class Read_array : public Read_value
+{
+  int before_read(json_engine_t *je, const char *value_name, String *err_buf)
+  {
+    if (json_scan_next(je) || je->state != JST_ARRAY_START)
+    {
+      err_buf->append(STRING_WITH_LEN("error reading "));
+      err_buf->append(value_name, strlen(value_name));
+      err_buf->append(STRING_WITH_LEN(" value"));
+      return 1;
+    }
+    return 0;
+  }
+
+  int after_read(int rc) { return rc > 0; }
+
+public:
+  bool read_value(json_engine_t *je, const char *value_name,
+                  String *err_buf) override
+  {
+    int rc= before_read(je, value_name, err_buf);
+    if (rc <= 0)
+      rc= read_container(je, err_buf);
+    return after_read(rc);
+  }
+  virtual int read_container(json_engine_t *je, String *err_buf)= 0;
+};
+
 }; /* namespace json_reader */
 
 #endif

From 676bfa7d14c7bf42a22485edd137b5b915e100bf Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Sat, 14 Mar 2026 11:14:45 +0200
Subject: [PATCH 47/50] Cherry-pick lost commit: Add unit test for
 json_read_object.

---
 sql/opt_context_store_replay.cc | 12 ++---
 sql/sql_json_lib.cc             |  7 ++-
 sql/sql_json_lib.h              | 13 +++---
 unittest/sql/CMakeLists.txt     |  6 +++
 unittest/sql/json_reader-t.cc   | 78 +++++++++++++++++++++++++++++++++
 5 files changed, 100 insertions(+), 16 deletions(-)
 create mode 100644 unittest/sql/json_reader-t.cc

diff --git a/sql/opt_context_store_replay.cc b/sql/opt_context_store_replay.cc
index fdc4aac35dce6..7e3f1a80a61f3 100644
--- a/sql/opt_context_store_replay.cc
+++ b/sql/opt_context_store_replay.cc
@@ -1118,7 +1118,7 @@ class Read_list_of_ranges : public Read_array
     while (je->state != JST_ARRAY_END)
     {
       char *value;
-      if (read_string(thd, je, "ranges", err_buf, value))
+      if (read_string(thd->mem_root, je, "ranges", err_buf, value))
         return 1;
 
       list_ranges->push_back(value);
@@ -1202,7 +1202,7 @@ static int parse_table_context(THD *thd, json_engine_t *je, String *err_buf,
   const char *err_msg= "Expected an object in the list_contexts array";
 
   Read_named_member array[]= {
-      {"name", Read_string(thd, &table_ctx->name), false},
+      {"name", Read_string(thd->mem_root, &table_ctx->name), false},
       {"file_stat_records",
        Read_non_neg_integer<ha_rows, ULONGLONG_MAX>(&table_ctx->file_stat_records),
        false},
@@ -1248,7 +1248,7 @@ static int parse_index_context(THD *thd, json_engine_t *je, String *err_buf,
   const char *err_msg= "Expected an object in the indexes array";
 
   Read_named_member array[]= {
-      {"index_name", Read_string(thd, &index_ctx->idx_name), false},
+      {"index_name", Read_string(thd->mem_root, &index_ctx->idx_name), false},
       {"rec_per_key", Read_list_of_ha_rows(thd, &index_ctx->list_rec_per_key),
        false},
       {NULL, Read_double(NULL), true}};
@@ -1275,7 +1275,7 @@ static int parse_range_context(THD *thd, json_engine_t *je, String *err_buf,
   const char *err_msg= "Expected an object in the list_ranges array";
 
   Read_named_member array[]= {
-      {"index_name", Read_string(thd, &out->idx_name), false},
+      {"index_name", Read_string(thd->mem_root, &out->idx_name), false},
       {"ranges", Read_list_of_ranges(thd, &out->range_list), false},
       {"num_rows",
        Read_non_neg_integer<ha_rows, ULONGLONG_MAX>(&out->rows),
@@ -1394,8 +1394,8 @@ static int parse_records_in_range_context(THD *thd, json_engine_t *je,
   Read_named_member array[]= {
       {"key_number", Read_non_neg_integer<uint, UINT_MAX>(&out->keynr),
        false},
-      {"min_key", Read_string(thd, &out->min_key), false},
-      {"max_key", Read_string(thd, &out->max_key), false},
+      {"min_key", Read_string(thd->mem_root, &out->min_key), false},
+      {"max_key", Read_string(thd->mem_root, &out->max_key), false},
       {"num_records",
        Read_non_neg_integer<ha_rows, ULONGLONG_MAX>(&out->records), false},
       {NULL, Read_double(NULL), true}};
diff --git a/sql/sql_json_lib.cc b/sql/sql_json_lib.cc
index 952d7eed0e806..570db1f67bb72 100644
--- a/sql/sql_json_lib.cc
+++ b/sql/sql_json_lib.cc
@@ -12,9 +12,8 @@
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1335
    USA */
 
+#include "my_global.h"
 #include "sql_json_lib.h"
-#include "mysql.h"
-#include "sql_select.h"
 
 namespace json_reader
 {
@@ -73,7 +72,7 @@ bool read_double(json_engine_t *je, const char *read_elem_key, String *err_buf,
     false  OK
     true  Parse Error
 */
-bool read_string(THD *thd, json_engine_t *je, const char *read_elem_key,
+bool read_string(MEM_ROOT *mem_root, json_engine_t *je, const char *read_elem_key,
                  String *err_buf, char *&value)
 {
   if (check_reading_of_elem_key(je, read_elem_key, err_buf))
@@ -89,7 +88,7 @@ bool read_string(THD *thd, json_engine_t *je, const char *read_elem_key,
     return true;
   }
 
-  value= strdup_root(thd->mem_root, val_buf.c_ptr_safe());
+  value= strdup_root(mem_root, val_buf.c_ptr_safe());
   return false;
 }
 
diff --git a/sql/sql_json_lib.h b/sql/sql_json_lib.h
index c1dce502b3550..4e4a6bb40da9d 100644
--- a/sql/sql_json_lib.h
+++ b/sql/sql_json_lib.h
@@ -15,10 +15,9 @@
 #ifndef SQL_JSON_LIB
 #define SQL_JSON_LIB
 
-#include "my_global.h"
 #include "json_lib.h"
 #include "sql_string.h"
-#include "table.h"
+#include "mysqld.h"                             /* system_charset_info */
 
 /*
   A syntax sugar interface to json_string_t
@@ -126,7 +125,7 @@ int json_read_object(json_engine_t *je, Read_named_member *members,
 namespace json_reader
 { /* Things to use with Read_named_member */
 
-bool read_string(THD *thd, json_engine_t *je, const char *read_elem_key,
+bool read_string(MEM_ROOT *mem_root, json_engine_t *je, const char *read_elem_key,
                  String *err_buf, char *&value);
 
 bool read_double(json_engine_t *je, const char *read_elem_key, String *err_buf,
@@ -152,14 +151,16 @@ class Read_value
 class Read_string : public Read_value
 {
   char **ptr;
-  THD *thd; /* The string will be allocated on thd->mem_root */
+  MEM_ROOT *mem_root; /* The string will be allocated on thd->mem_root */
 
 public:
-  Read_string(THD *thd_arg, char **ptr_arg) : ptr(ptr_arg), thd(thd_arg) {}
+  Read_string(MEM_ROOT *mem_root_arg, char **ptr_arg) :
+    ptr(ptr_arg), mem_root(mem_root_arg)
+  {}
   bool read_value(json_engine_t *je, const char *value_name,
                   String *err_buf) override
   {
-    return read_string(thd, je, value_name, err_buf, *ptr);
+    return read_string(mem_root, je, value_name, err_buf, *ptr);
   }
 };
 
diff --git a/unittest/sql/CMakeLists.txt b/unittest/sql/CMakeLists.txt
index 224ce83bae1d2..e32becc781b77 100644
--- a/unittest/sql/CMakeLists.txt
+++ b/unittest/sql/CMakeLists.txt
@@ -34,3 +34,9 @@ MY_ADD_TEST(mf_iocache)
 ADD_EXECUTABLE(my_json_writer-t my_json_writer-t.cc dummy_builtins.cc)
 TARGET_LINK_LIBRARIES(my_json_writer-t sql mytap)
 MY_ADD_TEST(my_json_writer)
+
+# Json writer needs String which needs sql library
+ADD_EXECUTABLE(json_reader-t json_reader-t.cc dummy_builtins.cc)
+TARGET_LINK_LIBRARIES(json_reader-t sql mytap)
+MY_ADD_TEST(jons_reader)
+
diff --git a/unittest/sql/json_reader-t.cc b/unittest/sql/json_reader-t.cc
new file mode 100644
index 0000000000000..72e6d1670957b
--- /dev/null
+++ b/unittest/sql/json_reader-t.cc
@@ -0,0 +1,78 @@
+/*
+   Copyright (c) 2026, MariaDB Corporation.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */
+
+#include <my_global.h>
+#include <my_pthread.h>
+#include <my_sys.h>
+#include <stdio.h>
+#include <tap.h>
+
+/*
+  Unit tests for json_read_object() 
+*/
+
+#include "../sql/sql_json_lib.h"
+#include "../sql/sql_json_lib.cc"
+
+using namespace json_reader;
+
+int main(int args, char **argv)
+{
+  MY_INIT(argv[0]);
+
+  plan(NO_PLAN);
+
+  diag("Testing json_read_object checks");
+  MEM_ROOT alloc;
+  json_engine_t je;
+  int rc;
+  init_alloc_root(0, &alloc, 32768, 0, 0);
+  mem_root_dynamic_array_init(&alloc, 0, &je.stack,
+                              sizeof(int), NULL, JSON_DEPTH_DEFAULT,
+                              JSON_DEPTH_INC, MYF(0));
+  system_charset_info= &my_charset_utf8mb3_bin;
+  const char *js_doc="{ \"str_val\": \"abc\", \"double_val\": 1234.5 }";
+  json_scan_start(&je, &my_charset_utf8mb3_bin, (const uchar *) js_doc,
+                  (const uchar *) js_doc + strlen(js_doc));
+  
+  char *parsed_name;
+  double parsed_dbl;
+  Read_named_member array[]= {
+      {"str_val",    Read_string(&alloc, &parsed_name), false},
+      {"double_val", Read_double(&parsed_dbl), false},
+      {NULL, Read_double(NULL), false }
+  };
+  String err_buf;
+
+  rc= json_read_object(&je, array, &err_buf);
+  ok(!rc, "Basic object read");
+  free_root(&alloc, 0);
+#if 0
+
+  {
+    Json_writer w;
+    w.start_object();
+    w.add_member("foo");
+    w.end_object();
+    ok(w.invalid_json, "Started a name but didn't add a value");
+  }
+
+#endif
+  diag("Done");
+
+  my_end(MY_CHECK_ERROR);
+  return exit_status();
+}

From 560d95f9d89fffc538c5e01da8f53ca2618d3e9e Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Sun, 15 Mar 2026 08:27:26 +0200
Subject: [PATCH 48/50] Cherry-pick lost commit: Make JSON parsing helpers
 accept MEM_ROOT* argument, not THD.

---
 sql/opt_context_store_replay.cc | 113 ++++++++++++++++----------------
 1 file changed, 56 insertions(+), 57 deletions(-)

diff --git a/sql/opt_context_store_replay.cc b/sql/opt_context_store_replay.cc
index 7e3f1a80a61f3..71ae4effc0a45 100644
--- a/sql/opt_context_store_replay.cc
+++ b/sql/opt_context_store_replay.cc
@@ -165,18 +165,20 @@ ST_FIELD_INFO optimizer_context_capture_info[]= {
 static void append_full_table_name(const TABLE_LIST *tbl, String *buf);
 static int parse_check_obj_start_in_array(json_engine_t *je, String *err_buf,
                                           const char *err_msg);
-static int parse_table_context(THD *thd, json_engine_t *je, String *err_buf,
+static int parse_table_context(MEM_ROOT *mem_root, json_engine_t *je,
+                               String *err_buf,
                                table_context_for_replay *table_ctx);
-static int parse_index_context(THD *thd, json_engine_t *je, String *err_buf,
+static int parse_index_context(MEM_ROOT *mem_root, json_engine_t *je,
+                               String *err_buf,
                                index_context_for_replay *index_ctx);
-static int parse_range_context(THD *thd, json_engine_t *je, String *err_buf,
+static int parse_range_context(MEM_ROOT *mem_root, json_engine_t *je, String *err_buf,
                                Multi_range_read_const_call_record *range_ctx);
-static int parse_index_read_cost_context(THD *thd, json_engine_t *je,
+static int parse_index_read_cost_context(MEM_ROOT*, json_engine_t *je,
                                          String *err_buf,
                                          cost_index_read_call_record *out);
-static bool parse_range_cost_estimate(THD *thd, json_engine_t *je,
+static bool parse_range_cost_estimate(MEM_ROOT*, json_engine_t *je,
                                       String *err_buf, Cost_estimate *cost);
-static int parse_records_in_range_context(THD *thd, json_engine_t *je,
+static int parse_records_in_range_context(MEM_ROOT *mem_root, json_engine_t *je,
                                           String *err_buf,
                                           records_in_range_call_record *rir_ctx);
 
@@ -1003,30 +1005,29 @@ class Saved_table_stats : public Sql_alloc
 // psergey: Reads a JSON object
 class Read_range_cost_estimate : public Read_value
 {
-  THD *thd;
+  MEM_ROOT *mem_root;
   Cost_estimate *ptr;
 
 public:
-  Read_range_cost_estimate(THD *thd_arg, Cost_estimate *ptr_arg)
-      : thd(thd_arg), ptr(ptr_arg)
-  {
-  }
+  Read_range_cost_estimate(MEM_ROOT *mem_root_arg, Cost_estimate *ptr_arg)
+      : mem_root(mem_root_arg), ptr(ptr_arg)
+  {}
   bool read_value(json_engine_t *je, const char *value_name,
                   String *err_buf) override
   {
-    return parse_range_cost_estimate(thd, je, err_buf, ptr);
+    return parse_range_cost_estimate(mem_root, je, err_buf, ptr);
   }
 };
 
-
+// psergey: reads an array of integers..
 class Read_list_of_ha_rows : public Read_array
 {
-  THD *thd;
+  MEM_ROOT *mem_root;
   List<ha_rows> *list_values;
 
 public:
-  Read_list_of_ha_rows(THD *thd_arg, List<ha_rows> *list_values_arg)
-      : thd(thd_arg), list_values(list_values_arg)
+  Read_list_of_ha_rows(MEM_ROOT *mem_root_arg, List<ha_rows> *list_values_arg)
+      : mem_root(mem_root_arg), list_values(list_values_arg)
   {
   }
   int read_container(json_engine_t *je, String *err_buf) override
@@ -1042,14 +1043,14 @@ class Read_list_of_ha_rows : public Read_array
         return 1;
       }
 
-      ha_rows *records_ptr= (ha_rows *) thd->alloc(sizeof(ha_rows));
+      ha_rows *records_ptr= (ha_rows *) alloc_root(mem_root, sizeof(ha_rows));
 
       if (unlikely(!records_ptr))
         return 1; // OOM
 
       *records_ptr= temp_value;
 
-      if (list_values->push_back(records_ptr) || json_scan_next(je))
+      if (list_values->push_back(records_ptr, mem_root) || json_scan_next(je))
         return 1;
     }
     return 0;
@@ -1062,15 +1063,15 @@ class Read_list_of_ha_rows : public Read_array
 */
 template <typename T> class Read_array_into_list : public Read_array
 {
-  THD *thd;
+  MEM_ROOT *mem_root;
   List<T> *list_ctx;
-  int (*parse_context_fn)(THD *, json_engine_t *, String *, T *);
+  int (*parse_context_fn)(MEM_ROOT *, json_engine_t *, String *, T *);
 
 public:
-  Read_array_into_list(THD *thd_arg, List<T> *list_ctx_arg,
-                       int (*parse_context_fn_arg)(THD *, json_engine_t *,
+  Read_array_into_list(MEM_ROOT *mem_root_arg, List<T> *list_ctx_arg,
+                       int (*parse_context_fn_arg)(MEM_ROOT *, json_engine_t *,
                                                    String *, T *))
-      : thd(thd_arg), list_ctx(list_ctx_arg),
+      : mem_root(mem_root_arg), list_ctx(list_ctx_arg),
         parse_context_fn(parse_context_fn_arg)
   {
   }
@@ -1085,31 +1086,26 @@ template <typename T> class Read_array_into_list : public Read_array
       if (unlikely(!ctx))
         return 1; // OOM
 
-      rc= parse_context_fn(thd, je, err_buf, ctx);
+      if ((rc= parse_context_fn(mem_root, je, err_buf, ctx)))
+        break; // Parse error
 
-      if (rc == 0)
-      {
-        if (list_ctx->push_back(ctx))
-          return 1; // OOM
-      }
-      else
-        break;
+      if (list_ctx->push_back(ctx, mem_root))
+        return 1; // OOM
     }
-
     return rc;
   }
 };
 
+// psergey-todo: this is just array of strings right?
 class Read_list_of_ranges : public Read_array
 {
-  THD *thd;
+  MEM_ROOT *mem_root;
   List<char> *list_ranges;
 
 public:
-  Read_list_of_ranges(THD *thd_arg, List<char> *list_ranges_arg)
-      : thd(thd_arg), list_ranges(list_ranges_arg)
-  {
-  }
+  Read_list_of_ranges(MEM_ROOT *mem_root_arg, List<char> *list_ranges_arg)
+    : mem_root(mem_root_arg), list_ranges(list_ranges_arg)
+  {}
   int read_container(json_engine_t *je, String *err_buf) override
   {
     if (json_scan_next(je))
@@ -1118,7 +1114,7 @@ class Read_list_of_ranges : public Read_array
     while (je->state != JST_ARRAY_END)
     {
       char *value;
-      if (read_string(thd->mem_root, je, "ranges", err_buf, value))
+      if (read_string(mem_root, je, "ranges", err_buf, value))
         return 1;
 
       list_ranges->push_back(value);
@@ -1196,13 +1192,14 @@ static int parse_context_obj_from_json_array(json_engine_t *je,
     1  Parse Error
    -1  EOF
 */
-static int parse_table_context(THD *thd, json_engine_t *je, String *err_buf,
+static int parse_table_context(MEM_ROOT *mem_root, json_engine_t *je,
+                               String *err_buf,
                                table_context_for_replay *table_ctx)
 {
   const char *err_msg= "Expected an object in the list_contexts array";
 
   Read_named_member array[]= {
-      {"name", Read_string(thd->mem_root, &table_ctx->name), false},
+      {"name", Read_string(mem_root, &table_ctx->name), false},
       {"file_stat_records",
        Read_non_neg_integer<ha_rows, ULONGLONG_MAX>(&table_ctx->file_stat_records),
        false},
@@ -1210,19 +1207,19 @@ static int parse_table_context(THD *thd, json_engine_t *je, String *err_buf,
       {"read_cost_cpu", Read_double(&table_ctx->read_cost_cpu), false},
       {"indexes",
        Read_array_into_list<index_context_for_replay>(
-           thd, &table_ctx->index_list, parse_index_context),
+           mem_root, &table_ctx->index_list, parse_index_context),
        true},
       {"list_ranges",
        Read_array_into_list<Multi_range_read_const_call_record>(
-           thd, &table_ctx->ranges_list, parse_range_context),
+           mem_root, &table_ctx->ranges_list, parse_range_context),
        true},
       {"list_index_read_costs",
        Read_array_into_list<cost_index_read_call_record>(
-           thd, &table_ctx->irc_list, parse_index_read_cost_context),
+           mem_root, &table_ctx->irc_list, parse_index_read_cost_context),
        true},
       {"list_records_in_range",
        Read_array_into_list<records_in_range_call_record>(
-           thd, &table_ctx->rir_list, parse_records_in_range_context),
+           mem_root, &table_ctx->rir_list, parse_records_in_range_context),
        true},
       {NULL, Read_double(NULL), true}};
 
@@ -1242,14 +1239,15 @@ static int parse_table_context(THD *thd, json_engine_t *je, String *err_buf,
     1  Parse Error
    -1  EOF
 */
-static int parse_index_context(THD *thd, json_engine_t *je, String *err_buf,
+static int parse_index_context(MEM_ROOT *mem_root, json_engine_t *je,
+                               String *err_buf,
                                index_context_for_replay *index_ctx)
 {
   const char *err_msg= "Expected an object in the indexes array";
 
   Read_named_member array[]= {
-      {"index_name", Read_string(thd->mem_root, &index_ctx->idx_name), false},
-      {"rec_per_key", Read_list_of_ha_rows(thd, &index_ctx->list_rec_per_key),
+      {"index_name", Read_string(mem_root, &index_ctx->idx_name), false},
+      {"rec_per_key", Read_list_of_ha_rows(mem_root, &index_ctx->list_rec_per_key),
        false},
       {NULL, Read_double(NULL), true}};
 
@@ -1269,18 +1267,18 @@ static int parse_index_context(THD *thd, json_engine_t *je, String *err_buf,
     1  Parse Error
    -1  EOF
 */
-static int parse_range_context(THD *thd, json_engine_t *je, String *err_buf,
+static int parse_range_context(MEM_ROOT *mem_root, json_engine_t *je, String *err_buf,
                                Multi_range_read_const_call_record *out)
 {
   const char *err_msg= "Expected an object in the list_ranges array";
 
   Read_named_member array[]= {
-      {"index_name", Read_string(thd->mem_root, &out->idx_name), false},
-      {"ranges", Read_list_of_ranges(thd, &out->range_list), false},
+      {"index_name", Read_string(mem_root, &out->idx_name), false},
+      {"ranges", Read_list_of_ranges(mem_root, &out->range_list), false},
       {"num_rows",
        Read_non_neg_integer<ha_rows, ULONGLONG_MAX>(&out->rows),
        false},
-      {"cost", Read_range_cost_estimate(thd, &out->cost), false},
+      {"cost", Read_range_cost_estimate(mem_root, &out->cost), false},
       {"max_index_blocks",
        Read_non_neg_integer<ha_rows, ULONGLONG_MAX>(&out->max_index_blocks),
        false},
@@ -1303,7 +1301,7 @@ static int parse_range_context(THD *thd, json_engine_t *je, String *err_buf,
     1  Parse Error
    -1  EOF
 */
-static bool parse_range_cost_estimate(THD *thd, json_engine_t *je,
+static bool parse_range_cost_estimate(MEM_ROOT*, json_engine_t *je,
                                       String *err_buf, Cost_estimate *cost)
 {
   if (json_scan_next(je) || je->state != JST_OBJ_START)
@@ -1342,7 +1340,7 @@ static bool parse_range_cost_estimate(THD *thd, json_engine_t *je,
     1  Parse Error
    -1  EOF
 */
-static int parse_index_read_cost_context(THD *thd, json_engine_t *je,
+static int parse_index_read_cost_context(MEM_ROOT* , json_engine_t *je,
                                          String *err_buf,
                                          cost_index_read_call_record *out)
 {
@@ -1385,7 +1383,8 @@ static int parse_index_read_cost_context(THD *thd, json_engine_t *je,
     1  Parse Error
    -1  EOF
 */
-static int parse_records_in_range_context(THD *thd, json_engine_t *je,
+static int parse_records_in_range_context(MEM_ROOT *mem_root,
+                                          json_engine_t *je,
                                           String *err_buf,
                                           records_in_range_call_record *out)
 {
@@ -1394,8 +1393,8 @@ static int parse_records_in_range_context(THD *thd, json_engine_t *je,
   Read_named_member array[]= {
       {"key_number", Read_non_neg_integer<uint, UINT_MAX>(&out->keynr),
        false},
-      {"min_key", Read_string(thd->mem_root, &out->min_key), false},
-      {"max_key", Read_string(thd->mem_root, &out->max_key), false},
+      {"min_key", Read_string(mem_root, &out->min_key), false},
+      {"max_key", Read_string(mem_root, &out->max_key), false},
       {"num_records",
        Read_non_neg_integer<ha_rows, ULONGLONG_MAX>(&out->records), false},
       {NULL, Read_double(NULL), true}};
@@ -1802,7 +1801,7 @@ bool Optimizer_context_replay::parse()
 
   Read_named_member array[]= {{"list_contexts",
                                Read_array_into_list<table_context_for_replay>(
-                                   thd, &ctx_list, parse_table_context),
+                                   thd->mem_root, &ctx_list, parse_table_context),
                                false},
                               {NULL, Read_double(NULL), true}};
 

From 467b06c9c03ae9f9d1e2a8a0c124e8d3c2c596f0 Mon Sep 17 00:00:00 2001
From: Sergei Petrunia <sergey@mariadb.com>
Date: Sun, 15 Mar 2026 12:03:42 +0200
Subject: [PATCH 49/50] Cherry-pick lost commit: Rename: Read_list_of_ranges to
 Read_array_of_strings and move it to sql_json_lib.

---
 sql/opt_context_store_replay.cc | 43 ++++++---------------------------
 sql/sql_json_lib.h              | 42 +++++++++++++++++++++++++++++---
 2 files changed, 46 insertions(+), 39 deletions(-)

diff --git a/sql/opt_context_store_replay.cc b/sql/opt_context_store_replay.cc
index 71ae4effc0a45..e0f9594a0dbca 100644
--- a/sql/opt_context_store_replay.cc
+++ b/sql/opt_context_store_replay.cc
@@ -1030,13 +1030,14 @@ class Read_list_of_ha_rows : public Read_array
       : mem_root(mem_root_arg), list_values(list_values_arg)
   {
   }
-  int read_container(json_engine_t *je, String *err_buf) override
+  int read_container(json_engine_t *je, const char *name, String *err_buf)
+    override
   {
     while (je->state != JST_ARRAY_END)
     {
       using json_reader::read_ha_rows_and_check_limit;
       ha_rows temp_value;
-      if (read_ha_rows_and_check_limit(je, "rec_per_key", err_buf, temp_value,
+      if (read_ha_rows_and_check_limit(je, name, err_buf, temp_value,
                                        ULONGLONG_MAX, "unsigned longlong",
                                        true))
       {
@@ -1058,8 +1059,8 @@ class Read_list_of_ha_rows : public Read_array
 };
 
 /*
-  Read an array of JSON objects representing object T. 
-  Create instances of T and collect them in a List<T> 
+  Read an array of JSON objects representing object T.
+  Create instances of T and collect them in a List<T>
 */
 template <typename T> class Read_array_into_list : public Read_array
 {
@@ -1075,7 +1076,8 @@ template <typename T> class Read_array_into_list : public Read_array
         parse_context_fn(parse_context_fn_arg)
   {
   }
-  int read_container(json_engine_t *je, String *err_buf) override
+  int read_container(json_engine_t *je, const char *name, String *err_buf)
+    override
   {
     int rc;
 
@@ -1096,35 +1098,6 @@ template <typename T> class Read_array_into_list : public Read_array
   }
 };
 
-// psergey-todo: this is just array of strings right?
-class Read_list_of_ranges : public Read_array
-{
-  MEM_ROOT *mem_root;
-  List<char> *list_ranges;
-
-public:
-  Read_list_of_ranges(MEM_ROOT *mem_root_arg, List<char> *list_ranges_arg)
-    : mem_root(mem_root_arg), list_ranges(list_ranges_arg)
-  {}
-  int read_container(json_engine_t *je, String *err_buf) override
-  {
-    if (json_scan_next(je))
-      return 1;
-
-    while (je->state != JST_ARRAY_END)
-    {
-      char *value;
-      if (read_string(mem_root, je, "ranges", err_buf, value))
-        return 1;
-
-      list_ranges->push_back(value);
-      if (json_scan_next(je))
-        return 1;
-    }
-
-    return 0;
-  }
-};
 
 /*
   check if the next element being parsed is an object within an array.
@@ -1274,7 +1247,7 @@ static int parse_range_context(MEM_ROOT *mem_root, json_engine_t *je, String *er
 
   Read_named_member array[]= {
       {"index_name", Read_string(mem_root, &out->idx_name), false},
-      {"ranges", Read_list_of_ranges(mem_root, &out->range_list), false},
+      {"ranges", Read_array_of_strings(mem_root, &out->range_list), false},
       {"num_rows",
        Read_non_neg_integer<ha_rows, ULONGLONG_MAX>(&out->rows),
        false},
diff --git a/sql/sql_json_lib.h b/sql/sql_json_lib.h
index 4e4a6bb40da9d..817d74d1a5aae 100644
--- a/sql/sql_json_lib.h
+++ b/sql/sql_json_lib.h
@@ -233,8 +233,9 @@ class Read_non_neg_integer : public Read_value
 
 /*
   Extends the Read_value interface to read an array of elements.
-  Descendant classes implement read_container()
-  // TODO: make it read_array_elem ?
+
+  This class will just start reading the JSON array.
+  Reading of array members is done by descendant classes in read_container().
 */
 class Read_array : public Read_value
 {
@@ -258,10 +259,43 @@ class Read_array : public Read_value
   {
     int rc= before_read(je, value_name, err_buf);
     if (rc <= 0)
-      rc= read_container(je, err_buf);
+      rc= read_container(je, value_name, err_buf);
     return after_read(rc);
   }
-  virtual int read_container(json_engine_t *je, String *err_buf)= 0;
+  virtual int read_container(json_engine_t *je, const char *name,
+                             String *err_buf)= 0;
+};
+
+//
+// psergey-todo: why cannot this use Read_array_into_list ?
+class Read_array_of_strings : public Read_array
+{
+  MEM_ROOT *mem_root;
+  List<char> *strings;
+
+public:
+  Read_array_of_strings(MEM_ROOT *mem_root_arg, List<char> *list_ranges_arg)
+    : mem_root(mem_root_arg), strings(list_ranges_arg)
+  {}
+  int read_container(json_engine_t *je, const char *name, String *err_buf)
+      override
+  {
+    if (json_scan_next(je))
+      return 1;
+
+    while (je->state != JST_ARRAY_END)
+    {
+      char *value;
+      if (read_string(mem_root, je, name, err_buf, value))
+        return 1;
+
+      strings->push_back(value, mem_root);
+      if (json_scan_next(je))
+        return 1;
+    }
+
+    return 0;
+  }
 };
 
 }; /* namespace json_reader */

From b100fbf49a129437434bf3b8457a4bf17f4eaf69 Mon Sep 17 00:00:00 2001
From: bsrikanth-mariadb <srikanth.bondalapati@mariadb.com>
Date: Mon, 27 Apr 2026 08:43:24 +0530
Subject: [PATCH 50/50] MDEV-39412: parse error reading tabs in ranges

Note:
while reading from information_schema.optimizer_context one level of unescaping
is already done i.e. (\\t becomes \t or \\\\t becomes \\t)

w.r.t the MDEV, there are 2 problems: -

1.
When reading from the sql script file, json parser is not able to parse
the range value in json_read_value() from json_lib.c
"ranges": [
            "(b\t\t\t\t\t\t) <= (b) <= (b???????)"
          ],
mainly the \t\t stuff, and hence a warning.
It also stops loading the context into memory.
Since, a new table is created with empty data, and without context,
we get Impossible WHERE noticed after reading const tables

2.
There is unescaping call being made in read_string() from sql_json_lib.cc
while parsing of the context. With this \\t was becoming \t.
However, print_range() from opt_range.cc already does escaping of the values.
The value "b\t\t\t" was in fact produced as "\b\\t\\t\\t".
Later, we try to compare range values from the query and the context.

Here a mismatch a found because, in one case there was escaping,
and in the other case escaping got removed.

Solutions
=========
For Problem 1. have escaping for ranges.
This should be done while dumping range values into the context.

For Problem 2. Remove unscaping call in read_string().
---
 .../main/opt_context_replay_basic.result      | 30 ++++++++++++++
 mysql-test/main/opt_context_replay_basic.test | 40 ++++++++++++++++++-
 sql/opt_context_store_replay.cc               | 15 ++++---
 sql/sql_json_lib.cc                           | 12 +-----
 4 files changed, 80 insertions(+), 17 deletions(-)

diff --git a/mysql-test/main/opt_context_replay_basic.result b/mysql-test/main/opt_context_replay_basic.result
index 34f9b4d6d2271..f344e36364330 100644
--- a/mysql-test/main/opt_context_replay_basic.result
+++ b/mysql-test/main/opt_context_replay_basic.result
@@ -272,5 +272,35 @@ set optimizer_replay_context='opt_context';
 EXPLAIN SELECT MAX(a) FROM t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
+set optimizer_replay_context='';
+drop table t1;
+#
+# MDEV-39412: Failed to parse saved optimizer context: error reading ranges value
+#
+set optimizer_record_context=0;
+CREATE TABLE t1(
+a VARCHAR(8),
+b VARCHAR(8),
+KEY(A),
+KEY(B)
+);
+INSERT INTO t1 SELECT REPEAT('a',8), REPEAT('b',8) FROM seq_1_to_10;
+set optimizer_record_context=1;
+EXPLAIN 
+SELECT * FROM t1 FORCE INDEX(a,b) WHERE a LIKE 'a%' OR b LIKE 'b%' 
+ORDER BY a,b;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index_merge	a,b	a,b	35,35	NULL	10	Using sort_union(a,b); Using where; Using filesort
+select context into dumpfile "../../tmp/dump1.sql" 
+from information_schema.optimizer_context;
+drop table t1;
+set optimizer_replay_context='opt_context';
+# Same query as above, must have same explain:
+EXPLAIN 
+SELECT * FROM t1 FORCE INDEX(a,b) WHERE a LIKE 'a%' OR b LIKE 'b%' 
+ORDER BY a,b;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index_merge	a,b	a,b	35,35	NULL	10	Using sort_union(a,b); Using where; Using filesort
+set optimizer_replay_context='';
 drop table t1;
 drop database db1;
diff --git a/mysql-test/main/opt_context_replay_basic.test b/mysql-test/main/opt_context_replay_basic.test
index dcf85929c337b..2575bd4f92802 100644
--- a/mysql-test/main/opt_context_replay_basic.test
+++ b/mysql-test/main/opt_context_replay_basic.test
@@ -68,8 +68,8 @@ set optimizer_replay_context='opt_context';
 --echo # Same query as above, must have same explain:
 EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE a = 1;
 
-set optimizer_replay_context='';
 --remove_file "$MYSQLTEST_VARDIR/tmp/dump1.sql"
+set optimizer_replay_context='';
 drop table t1;
 
 --echo #
@@ -116,6 +116,44 @@ set optimizer_replay_context='opt_context';
 --echo # Same query as above, must have same explain:
 EXPLAIN SELECT MAX(a) FROM t1;
 
+set optimizer_replay_context='';
+--remove_file "$MYSQLTEST_VARDIR/tmp/dump1.sql"
+drop table t1;
+
+--echo #
+--echo # MDEV-39412: Failed to parse saved optimizer context: error reading ranges value
+--echo #
+set optimizer_record_context=0;
+
+CREATE TABLE t1(
+    a VARCHAR(8),
+    b VARCHAR(8),
+    KEY(A),
+    KEY(B)
+);
+INSERT INTO t1 SELECT REPEAT('a',8), REPEAT('b',8) FROM seq_1_to_10;
+
+set optimizer_record_context=1;
+EXPLAIN 
+SELECT * FROM t1 FORCE INDEX(a,b) WHERE a LIKE 'a%' OR b LIKE 'b%' 
+ORDER BY a,b;
+
+select context into dumpfile "../../tmp/dump1.sql" 
+from information_schema.optimizer_context;
+drop table t1;
+
+--disable_query_log
+--disable_result_log
+--source "$MYSQLTEST_VARDIR/tmp/dump1.sql"
+--enable_query_log
+--enable_result_log
+set optimizer_replay_context='opt_context';
+--echo # Same query as above, must have same explain:
+EXPLAIN 
+SELECT * FROM t1 FORCE INDEX(a,b) WHERE a LIKE 'a%' OR b LIKE 'b%' 
+ORDER BY a,b;
+
+set optimizer_replay_context='';
 --remove_file "$MYSQLTEST_VARDIR/tmp/dump1.sql"
 drop table t1;
 
diff --git a/sql/opt_context_store_replay.cc b/sql/opt_context_store_replay.cc
index e0f9594a0dbca..7355b7d1f4a50 100644
--- a/sql/opt_context_store_replay.cc
+++ b/sql/opt_context_store_replay.cc
@@ -255,13 +255,18 @@ void dump_mrr_info_calls(List<Multi_range_read_const_call_record> *mrr_list,
   {
     Json_writer_object irc_wrapper(ctx_writer);
     irc_wrapper.add("index_name", irc->idx_name);
-
+    List_iterator rc_li(irc->range_list);
+    Json_writer_array ranges_wrapper(ctx_writer, "ranges");
+    while (const char *range_str= rc_li++)
     {
-      Json_writer_array ranges_wrapper(ctx_writer, "ranges");
-      List_iterator rc_li(irc->range_list);
-      while (const char *range_str= rc_li++)
-        ranges_wrapper.add(range_str, strlen(range_str));
+      const String range_info(range_str, strlen(range_str),
+                              system_charset_info);
+      StringBuffer<128> escaped_range_info;
+      json_escape_to_string(&range_info, &escaped_range_info);
+      ranges_wrapper.add(escaped_range_info.c_ptr_safe(),
+                         escaped_range_info.length());
     }
+    ranges_wrapper.end();
 
     irc_wrapper.add("num_rows", irc->rows);
     {
diff --git a/sql/sql_json_lib.cc b/sql/sql_json_lib.cc
index 570db1f67bb72..8648a17ce6042 100644
--- a/sql/sql_json_lib.cc
+++ b/sql/sql_json_lib.cc
@@ -78,17 +78,7 @@ bool read_string(MEM_ROOT *mem_root, json_engine_t *je, const char *read_elem_ke
   if (check_reading_of_elem_key(je, read_elem_key, err_buf))
     return true;
 
-  StringBuffer<128> val_buf;
-  if (json_unescape_to_string((const char *) je->value, je->value_len,
-                              &val_buf))
-  {
-    err_buf->append(STRING_WITH_LEN("un-escaping error of "));
-    err_buf->append(read_elem_key, strlen(read_elem_key));
-    err_buf->append(STRING_WITH_LEN(" element"));
-    return true;
-  }
-
-  value= strdup_root(mem_root, val_buf.c_ptr_safe());
+  value= strmake_root(mem_root, (const char *) je->value, je->value_len);
   return false;
 }