MDEV-31812 Add switch to old_mode to disable non-locking ALTER

Add LOCK_ALTER_TABE_COPY bit to old_mode. Disables online copy by default,
but still allows to force it with explicit lock=none

mysql-test/main/alter_table_online_debug.result

@@ -1416,6 +1416,46 @@ id	a	b
 2	1	
 drop table t;
 set debug_sync= reset;
+#
+# MDEV-31812 Add switch to old_mode to disable non-locking ALTER
+#
+set @old_old_mode= @@old_mode;
+create or replace table t1 (a int primary key, b int);
+set debug_sync= 'alter_table_copy_end SIGNAL copy_end WAIT_FOR proceed';
+alter table t1 drop primary key, add primary key(b), algorithm= copy;
+connection con2;
+set debug_sync= 'now WAIT_FOR copy_end';
+select if(max_stage = 4, "online", "old") as mode
+from information_schema.processlist where id = @con;
+mode
+online
+set debug_sync= 'now SIGNAL proceed';
+connection default;
+set old_mode= LOCK_ALTER_TABLE_COPY;
+set debug_sync= 'alter_table_copy_end SIGNAL copy_end WAIT_FOR proceed';
+alter table t1 drop primary key, add primary key(b), algorithm= copy;
+connection con2;
+set debug_sync= 'now WAIT_FOR copy_end';
+select if(max_stage = 4, "online", "old") as mode
+from information_schema.processlist where id = @con;
+mode
+old
+set debug_sync= 'now SIGNAL proceed';
+connection default;
+set debug_sync= 'alter_table_copy_end SIGNAL copy_end WAIT_FOR proceed';
+alter table t1 drop primary key, add primary key(b),
+algorithm= copy, lock=none;
+connection con2;
+set debug_sync= 'now WAIT_FOR copy_end';
+select if(max_stage = 4, "online", "old") as mode
+from information_schema.processlist where id = @con;
+mode
+online
+set debug_sync= 'now SIGNAL proceed';
+connection default;
+set old_mode= @old_old_mode;
+drop table t1;
+set debug_sync= reset;
 disconnect con1;
 disconnect con2;
 #

mysql-test/main/alter_table_online_debug.test

@@ -1650,6 +1650,52 @@ select * from t;
 drop table t;
 set debug_sync= reset;
 
+--echo #
+--echo # MDEV-31812 Add switch to old_mode to disable non-locking ALTER
+--echo #
+set @old_old_mode= @@old_mode;
+create or replace table t1 (a int primary key, b int);
+set debug_sync= 'alter_table_copy_end SIGNAL copy_end WAIT_FOR proceed';
+send alter table t1 drop primary key, add primary key(b), algorithm= copy;
+
+--connection con2
+set debug_sync= 'now WAIT_FOR copy_end';
+select if(max_stage = 4, "online", "old") as mode
+        from information_schema.processlist where id = @con;
+set debug_sync= 'now SIGNAL proceed';
+
+--connection default
+--reap
+
+set old_mode= LOCK_ALTER_TABLE_COPY;
+set debug_sync= 'alter_table_copy_end SIGNAL copy_end WAIT_FOR proceed';
+send alter table t1 drop primary key, add primary key(b), algorithm= copy;
+--connection con2
+set debug_sync= 'now WAIT_FOR copy_end';
+select if(max_stage = 4, "online", "old") as mode
+        from information_schema.processlist where id = @con;
+set debug_sync= 'now SIGNAL proceed';
+
+--connection default
+--reap
+
+set debug_sync= 'alter_table_copy_end SIGNAL copy_end WAIT_FOR proceed';
+send alter table t1 drop primary key, add primary key(b),
+        algorithm= copy, lock=none;
+--connection con2
+set debug_sync= 'now WAIT_FOR copy_end';
+
+select if(max_stage = 4, "online", "old") as mode
+        from information_schema.processlist where id = @con;
+set debug_sync= 'now SIGNAL proceed';
+
+--connection default
+--reap
+set old_mode= @old_old_mode;
+drop table t1;
+set debug_sync= reset;
+
+
 --disconnect con1
 --disconnect con2
 --echo #

mysql-test/main/mysqld--help.result

@@ -709,7 +709,8 @@ The following specify which files/extra groups are read (specified before remain
  MySQL versions. Any combination of: 
  NO_DUP_KEY_WARNINGS_WITH_IGNORE, NO_PROGRESS_INFO, 
  ZERO_DATE_TIME_CAST, UTF8_IS_UTF8MB3, 
- IGNORE_INDEX_ONLY_FOR_JOIN, COMPAT_5_1_CHECKSUM
+ IGNORE_INDEX_ONLY_FOR_JOIN, COMPAT_5_1_CHECKSUM, 
+ LOCK_ALTER_TABLE_COPY
  --old-passwords     Use old password encryption method (needed for 4.0 and
  older clients)
  --old-style-user-limits 

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

@@ -114,8 +114,8 @@ SET @@global.old_mode = 4;
 SELECT @@global.old_mode;
 @@global.old_mode
 ZERO_DATE_TIME_CAST
-SET @@global.old_mode = 64;
-ERROR 42000: Variable 'old_mode' can't be set to the value of '64'
+SET @@global.old_mode = 128;
+ERROR 42000: Variable 'old_mode' can't be set to the value of '128'
 SELECT @@global.old_mode;
 @@global.old_mode
 ZERO_DATE_TIME_CAST

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

@@ -2289,7 +2289,7 @@ VARIABLE_COMMENT	Used to emulate old behavior from earlier MariaDB or MySQL vers
 NUMERIC_MIN_VALUE	NULL
 NUMERIC_MAX_VALUE	NULL
 NUMERIC_BLOCK_SIZE	NULL
-ENUM_VALUE_LIST	NO_DUP_KEY_WARNINGS_WITH_IGNORE,NO_PROGRESS_INFO,ZERO_DATE_TIME_CAST,UTF8_IS_UTF8MB3,IGNORE_INDEX_ONLY_FOR_JOIN,COMPAT_5_1_CHECKSUM
+ENUM_VALUE_LIST	NO_DUP_KEY_WARNINGS_WITH_IGNORE,NO_PROGRESS_INFO,ZERO_DATE_TIME_CAST,UTF8_IS_UTF8MB3,IGNORE_INDEX_ONLY_FOR_JOIN,COMPAT_5_1_CHECKSUM,LOCK_ALTER_TABLE_COPY
 READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	OLD_PASSWORDS

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

@@ -2489,7 +2489,7 @@ VARIABLE_COMMENT	Used to emulate old behavior from earlier MariaDB or MySQL vers
 NUMERIC_MIN_VALUE	NULL
 NUMERIC_MAX_VALUE	NULL
 NUMERIC_BLOCK_SIZE	NULL
-ENUM_VALUE_LIST	NO_DUP_KEY_WARNINGS_WITH_IGNORE,NO_PROGRESS_INFO,ZERO_DATE_TIME_CAST,UTF8_IS_UTF8MB3,IGNORE_INDEX_ONLY_FOR_JOIN,COMPAT_5_1_CHECKSUM
+ENUM_VALUE_LIST	NO_DUP_KEY_WARNINGS_WITH_IGNORE,NO_PROGRESS_INFO,ZERO_DATE_TIME_CAST,UTF8_IS_UTF8MB3,IGNORE_INDEX_ONLY_FOR_JOIN,COMPAT_5_1_CHECKSUM,LOCK_ALTER_TABLE_COPY
 READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	OLD_PASSWORDS

mysql-test/suite/sys_vars/t/old_mode_basic.test

@@ -172,7 +172,7 @@ SET @@global.old_mode = 4;
 SELECT @@global.old_mode;
 
 --Error ER_WRONG_VALUE_FOR_VAR
-SET @@global.old_mode = 64;
+SET @@global.old_mode = 128;
 SELECT @@global.old_mode;
 
 # use of decimal values

sql/sql_class.h

@@ -202,6 +202,7 @@ enum enum_binlog_row_image {
 #define OLD_MODE_UTF8_IS_UTF8MB3      (1 << 3)
 #define OLD_MODE_IGNORE_INDEX_ONLY_FOR_JOIN          (1 << 4)
 #define OLD_MODE_COMPAT_5_1_CHECKSUM    (1 << 5)
+#define OLD_MODE_LOCK_ALTER_TABLE_COPY                   (1 << 6)
 
 extern char internal_table_name[2];
 extern char empty_c_string[1];

sql/sql_table.cc

@@ -10172,7 +10172,9 @@ bool mysql_alter_table(THD *thd, const LEX_CSTRING *new_db,
   */
   table_list->required_type= TABLE_TYPE_NORMAL;
 
-  if (alter_info->requested_lock > Alter_info::ALTER_TABLE_LOCK_NONE
+  if ((alter_info->requested_lock == Alter_info::ALTER_TABLE_LOCK_DEFAULT
+       && (thd->variables.old_behavior & OLD_MODE_LOCK_ALTER_TABLE_COPY))
+      || alter_info->requested_lock > Alter_info::ALTER_TABLE_LOCK_NONE
       || thd->lex->sql_command == SQLCOM_OPTIMIZE
       || alter_info->algorithm(thd) > Alter_info::ALTER_TABLE_ALGORITHM_COPY)
     online= false;

sql/sys_vars.cc

@@ -3891,6 +3891,7 @@ static const char *old_mode_names[]=
   "UTF8_IS_UTF8MB3",
   "IGNORE_INDEX_ONLY_FOR_JOIN",
   "COMPAT_5_1_CHECKSUM",
+  "LOCK_ALTER_TABLE_COPY",
   0
 };