MDEV-27735 Deprecate the parameter innodb_change_buffering

As a follow-up to MDEV-27734 Set innodb_change_buffering=none by default
we mark the option innodb_change_buffering deprecated, to inform users
of its future removal.

mysql-test/suite/encryption/r/innodb_encrypt_log.result

@@ -21,7 +21,6 @@ Warning	1478	Ignoring encryption parameter during temporary table creation.
 INSERT INTO t VALUES
 (NULL,1,1,'private','secret'),(NULL,2,2,'sacred','success'),
 (NULL,3,3,'story','secure'),(NULL,4,4,'security','sacrament');
-SET GLOBAL innodb_change_buffering=none;
 SET GLOBAL innodb_flush_log_at_trx_commit=1;
 INSERT INTO t0
 SELECT NULL, t1.col_int, t1.col_int_key, t1.col_char, t1.col_char_key

mysql-test/suite/encryption/t/innodb_encrypt_log.test

@@ -29,11 +29,6 @@ INSERT INTO t VALUES
 (NULL,1,1,'private','secret'),(NULL,2,2,'sacred','success'),
 (NULL,3,3,'story','secure'),(NULL,4,4,'security','sacrament');
 
-# Prevent change buffering of key(col_char_key), so that
-# after the restart, the data ('secret','success','secure','sacrament')
-# cannot be emitted to the unencrypted redo log by change buffer merge.
-SET GLOBAL innodb_change_buffering=none;
-
 # Force a redo log flush at the next commit.
 SET GLOBAL innodb_flush_log_at_trx_commit=1;
 INSERT INTO t0

mysql-test/suite/innodb/r/ibuf_not_empty.result

@@ -6,6 +6,8 @@ INDEX(b))
 ENGINE=InnoDB STATS_PERSISTENT=0;
 SET GLOBAL innodb_change_buffering_debug = 1;
 SET GLOBAL innodb_change_buffering=all;
+Warnings:
+Warning	138	The parameter innodb_change_buffering is deprecated
 INSERT INTO t1 SELECT 0,'x',1 FROM seq_1_to_1024;
 # restart: --innodb-force-recovery=6 --innodb-change-buffer-dump
 check table t1;

mysql-test/suite/innodb/r/innodb-change-buffer-recovery.result

@@ -14,6 +14,8 @@ INDEX(b))
 ENGINE=InnoDB STATS_PERSISTENT=0;
 SET GLOBAL innodb_change_buffering_debug = 1;
 SET GLOBAL innodb_change_buffering = all;
+Warnings:
+Warning	138	The parameter innodb_change_buffering is deprecated
 INSERT INTO t1 SELECT 0,'x',1 FROM seq_1_to_8192;
 BEGIN;
 SELECT b FROM t1 LIMIT 3;

mysql-test/suite/sys_vars/r/innodb_change_buffering_basic.result

@@ -24,6 +24,8 @@ select * from information_schema.session_variables where variable_name='innodb_c
 VARIABLE_NAME	VARIABLE_VALUE
 INNODB_CHANGE_BUFFERING	none
 set global innodb_change_buffering='none';
+Warnings:
+Warning	138	The parameter innodb_change_buffering is deprecated
 select @@global.innodb_change_buffering;
 @@global.innodb_change_buffering
 none
@@ -34,6 +36,8 @@ select * from information_schema.session_variables where variable_name='innodb_c
 VARIABLE_NAME	VARIABLE_VALUE
 INNODB_CHANGE_BUFFERING	none
 set @@global.innodb_change_buffering='inserts';
+Warnings:
+Warning	138	The parameter innodb_change_buffering is deprecated
 select @@global.innodb_change_buffering;
 @@global.innodb_change_buffering
 inserts
@@ -50,6 +54,8 @@ ERROR HY000: Variable 'innodb_change_buffering' is a GLOBAL variable and should
 set global innodb_change_buffering=1.1;
 ERROR 42000: Incorrect argument type to variable 'innodb_change_buffering'
 set global innodb_change_buffering=1;
+Warnings:
+Warning	138	The parameter innodb_change_buffering is deprecated
 SELECT @@global.innodb_change_buffering;
 @@global.innodb_change_buffering
 inserts
@@ -60,6 +66,8 @@ ERROR 42000: Incorrect argument type to variable 'innodb_change_buffering'
 set global innodb_change_buffering='some';
 ERROR 42000: Variable 'innodb_change_buffering' can't be set to the value of 'some'
 SET @@global.innodb_change_buffering = @start_global_value;
+Warnings:
+Warning	138	The parameter innodb_change_buffering is deprecated
 SELECT @@global.innodb_change_buffering;
 @@global.innodb_change_buffering
 none

mysql-test/suite/sys_vars/r/sysvars_innodb.result

@@ -230,7 +230,7 @@ SESSION_VALUE	NULL
 DEFAULT_VALUE	none
 VARIABLE_SCOPE	GLOBAL
 VARIABLE_TYPE	ENUM
-VARIABLE_COMMENT	Buffer changes to secondary indexes.
+VARIABLE_COMMENT	Buffer changes to secondary indexes (deprecated).
 NUMERIC_MIN_VALUE	NULL
 NUMERIC_MAX_VALUE	NULL
 NUMERIC_BLOCK_SIZE	NULL

storage/innobase/handler/ha_innodb.cc

@@ -417,6 +417,14 @@ static TYPELIB innodb_change_buffering_typelib = {
 	NULL
 };
 
+static void innodb_change_buffering_deprecated(THD *thd, st_mysql_sys_var*,
+                                               void *var_ptr, const void *save)
+{
+  push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN, HA_ERR_UNSUPPORTED,
+                      "The parameter innodb_change_buffering is deprecated");
+  *static_cast<ulong*>(var_ptr) = *static_cast<const ulong*>(save);
+}
+
 /** Allowed values of innodb_instant_alter_column_allowed */
 const char* innodb_instant_alter_column_allowed_names[] = {
 	"never", /* compatible with MariaDB 5.5 to 10.2 */
@@ -19365,8 +19373,9 @@ static MYSQL_SYSVAR_BOOL(numa_interleave, srv_numa_interleave,
 
 static MYSQL_SYSVAR_ENUM(change_buffering, innodb_change_buffering,
   PLUGIN_VAR_RQCMDARG,
-  "Buffer changes to secondary indexes.",
-  NULL, NULL, IBUF_USE_NONE, &innodb_change_buffering_typelib);
+  "Buffer changes to secondary indexes (deprecated).",
+  nullptr, innodb_change_buffering_deprecated, IBUF_USE_NONE,
+  &innodb_change_buffering_typelib);
 
 static MYSQL_SYSVAR_UINT(change_buffer_max_size,
   srv_change_buffer_max_size,