MDEV-18650: Options deprecated in previous versions - old_alter_table

It was deprecated in 5.5 but it never issued a deprecation warning.
Make it issue a warning in 10.5.1.

mysql-test/main/alter_table.result

@@ -1679,6 +1679,8 @@ ALTER TABLE t1 DROP INDEX i1, DROP INDEX i2, DROP INDEX i3, DROP INDEX i4;
 #
 SET SESSION old_alter_table= 1;
 affected rows: 0
+Warnings:
+Warning	1287	'@@old_alter_table' is deprecated and will be removed in a future release. Please use '@@alter_algorithm' instead
 ALTER TABLE t1 ADD INDEX i1(b);
 affected rows: 2
 info: Records: 2  Duplicates: 0  Warnings: 0
@@ -1699,6 +1701,8 @@ Warnings:
 Note	1831	Duplicate index `i4`. This is deprecated and will be disallowed in a future release
 SET SESSION old_alter_table= 0;
 affected rows: 0
+Warnings:
+Warning	1287	'@@old_alter_table' is deprecated and will be removed in a future release. Please use '@@alter_algorithm' instead
 ALTER TABLE t1 DROP INDEX i1, DROP INDEX i2, DROP INDEX i3, DROP INDEX i4;
 #
 # 3: Test unsupported in-place operation

mysql-test/main/innodb_mysql_sync.result

@@ -450,6 +450,8 @@ info: Records: 0  Duplicates: 0  Warnings: 0
 #table copy when the old_alter_table enabled.
 SET SESSION old_alter_table= TRUE;
 affected rows: 0
+Warnings:
+Warning	1287	'@@old_alter_table' is deprecated and will be removed in a future release. Please use '@@alter_algorithm' instead
 ALTER TABLE t1 FORCE;
 affected rows: 1
 info: Records: 1  Duplicates: 0  Warnings: 0
@@ -474,6 +476,8 @@ SET DEBUG_SYNC= 'RESET';
 affected rows: 0
 SET SESSION old_alter_table= FALSE;
 affected rows: 0
+Warnings:
+Warning	1287	'@@old_alter_table' is deprecated and will be removed in a future release. Please use '@@alter_algorithm' instead
 #ALTER TABLE FORCE and ALTER TABLE ENGINE uses table copy
 #when ALGORITHM COPY is used.
 ALTER TABLE t1 FORCE, ALGORITHM= COPY;

mysql-test/suite/innodb/r/innodb_bug53592.result

@@ -1,4 +1,6 @@
 set old_alter_table=0;
+Warnings:
+Warning	1287	'@@old_alter_table' is deprecated and will be removed in a future release. Please use '@@alter_algorithm' instead
 create table bug53592(a int) engine=innodb row_format=compact;
 alter table bug53592 add column b text charset utf8;
 alter table bug53592 add column c blob not null;
@@ -13,6 +15,8 @@ Table	Op	Msg_type	Msg_text
 test.bug53592	check	status	OK
 drop table bug53592;
 set old_alter_table=1;
+Warnings:
+Warning	1287	'@@old_alter_table' is deprecated and will be removed in a future release. Please use '@@alter_algorithm' instead
 create table bug53592(a int) engine=innodb row_format=compact;
 alter table bug53592 add column b text charset utf8;
 alter table bug53592 add column c blob not null;

mysql-test/suite/innodb_zip/r/bug53591.result

@@ -2,6 +2,8 @@ call mtr.add_suppression('InnoDB: Cannot add field.*because after adding it, the
 SET GLOBAL innodb_file_per_table=on;
 SET GLOBAL innodb_strict_mode=on;
 set old_alter_table=0;
+Warnings:
+Warning	1287	'@@old_alter_table' is deprecated and will be removed in a future release. Please use '@@alter_algorithm' instead
 CREATE TABLE bug53591(a text charset utf8 not null)
 ENGINE=InnoDB KEY_BLOCK_SIZE=1;
 ALTER TABLE bug53591 ADD PRIMARY KEY(a(220));

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

@@ -21,7 +21,11 @@ select * from information_schema.session_variables where variable_name='old_alte
 VARIABLE_NAME	VARIABLE_VALUE
 OLD_ALTER_TABLE	DEFAULT
 set global old_alter_table=1;
+Warnings:
+Warning	1287	'@@old_alter_table' is deprecated and will be removed in a future release. Please use '@@alter_algorithm' instead
 set session old_alter_table=1;
+Warnings:
+Warning	1287	'@@old_alter_table' is deprecated and will be removed in a future release. Please use '@@alter_algorithm' instead
 select @@global.old_alter_table;
 @@global.old_alter_table
 COPY
@@ -41,7 +45,11 @@ select * from information_schema.session_variables where variable_name='old_alte
 VARIABLE_NAME	VARIABLE_VALUE
 OLD_ALTER_TABLE	COPY
 set global old_alter_table=2;
+Warnings:
+Warning	1287	'@@old_alter_table' is deprecated and will be removed in a future release. Please use '@@alter_algorithm' instead
 set session old_alter_table=2;
+Warnings:
+Warning	1287	'@@old_alter_table' is deprecated and will be removed in a future release. Please use '@@alter_algorithm' instead
 select @@global.old_alter_table;
 @@global.old_alter_table
 INPLACE
@@ -61,7 +69,11 @@ select * from information_schema.session_variables where variable_name='old_alte
 VARIABLE_NAME	VARIABLE_VALUE
 OLD_ALTER_TABLE	INPLACE
 set global old_alter_table=3;
+Warnings:
+Warning	1287	'@@old_alter_table' is deprecated and will be removed in a future release. Please use '@@alter_algorithm' instead
 set session old_alter_table=3;
+Warnings:
+Warning	1287	'@@old_alter_table' is deprecated and will be removed in a future release. Please use '@@alter_algorithm' instead
 select @@global.old_alter_table;
 @@global.old_alter_table
 NOCOPY
@@ -81,7 +93,11 @@ select * from information_schema.session_variables where variable_name='old_alte
 VARIABLE_NAME	VARIABLE_VALUE
 OLD_ALTER_TABLE	NOCOPY
 set global old_alter_table=4;
+Warnings:
+Warning	1287	'@@old_alter_table' is deprecated and will be removed in a future release. Please use '@@alter_algorithm' instead
 set session old_alter_table=4;
+Warnings:
+Warning	1287	'@@old_alter_table' is deprecated and will be removed in a future release. Please use '@@alter_algorithm' instead
 select @@global.old_alter_table;
 @@global.old_alter_table
 INSTANT
@@ -107,6 +123,8 @@ ERROR 42000: Incorrect argument type to variable 'old_alter_table'
 set global old_alter_table="foo";
 ERROR 42000: Variable 'old_alter_table' can't be set to the value of 'foo'
 SET @@global.old_alter_table = @start_global_value;
+Warnings:
+Warning	1287	'@@old_alter_table' is deprecated and will be removed in a future release. Please use '@@alter_algorithm' instead
 SELECT @@global.old_alter_table;
 @@global.old_alter_table
 DEFAULT

sql/sys_vars.cc

@@ -2486,7 +2486,9 @@ static Sys_var_enum Sys_old_alter_table(
        "old_alter_table", "Alias for alter_algorithm. "
        "Deprecated. Use --alter-algorithm instead.",
        SESSION_VAR(alter_algorithm), CMD_LINE(OPT_ARG),
-       alter_algorithm_modes, DEFAULT(0));
+       alter_algorithm_modes, DEFAULT(0), NO_MUTEX_GUARD, NOT_IN_BINLOG,
+       ON_CHECK(0), ON_UPDATE(0),
+       DEPRECATED("'@@alter_algorithm'")); // Since 10.5.1
 
 static bool check_old_passwords(sys_var *self, THD *thd, set_var *var)
 {