Fixes of MDEV-30538 and MDEV-30586 for 10.4 adjusted for 11.0.

The commits for MDEV-30538 and MDEV-30586 could not be cherry-picked into
11.0 separately.

Author: igorbabaev

mysql-test/main/delete.result

@@ -583,7 +583,8 @@ explain delete from t1
 where exists (select 'X' from t1 a where a.c2 = t1.c2) and c2 >= 3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	Using where
-2	DEPENDENT SUBQUERY	a	ALL	NULL	NULL	NULL	NULL	8	Using where
+1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	4	func	1	
+2	MATERIALIZED	a	ALL	NULL	NULL	NULL	NULL	8	
 delete from t1
 where exists (select 'X' from t1 a where a.c2 = t1.c2) and c2 >= 3;
 select *from t1;
@@ -599,7 +600,8 @@ where exists (select 'X' from t1 a where a.c2 = t1.c2) and c2 >= 3
 order by c2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	Using where
-2	DEPENDENT SUBQUERY	a	ALL	NULL	NULL	NULL	NULL	8	Using where
+1	PRIMARY	<subquery2>	eq_ref	distinct_key	distinct_key	4	func	1	
+2	MATERIALIZED	a	ALL	NULL	NULL	NULL	NULL	8	
 delete from t1
 where exists (select 'X' from t1 a where a.c2 = t1.c2) and c2 >= 3
 order by c2;

mysql-test/main/multi_update.result

@@ -1269,8 +1269,7 @@ EXPLAIN
 DROP TABLES t1, t2;
 # End of 10.3 tests
 #
-# MDEV-28538: multi-table UPDATE/DELETE with possible exists-to-in
-#
+# MDEV-30538: multi-table UPDATE/DELETE with possible exists-to-in
 create table t1 (c1 int, c2 int, c3 int, index idx(c2));
 insert into t1 values
 (1,1,1),(3,2,2),(1,3,3),

mysql-test/main/multi_update.test

@@ -1135,7 +1135,7 @@ DROP TABLES t1, t2;
 --echo # End of 10.3 tests
 
 --echo #
---echo # MDEV-28538: multi-table UPDATE/DELETE with possible exists-to-in
+--echo # MDEV-30538: multi-table UPDATE/DELETE with possible exists-to-in
 --echo #
 
 create table t1 (c1 int, c2 int, c3 int, index idx(c2));

sql/item_subselect.cc

@@ -2953,7 +2953,9 @@ bool Item_exists_subselect::select_prepare_to_be_in()
   if (!optimizer &&
       (thd->lex->sql_command == SQLCOM_SELECT ||
        thd->lex->sql_command == SQLCOM_UPDATE_MULTI ||
-       thd->lex->sql_command == SQLCOM_DELETE_MULTI) &&
+       thd->lex->sql_command == SQLCOM_DELETE_MULTI ||
+       thd->lex->sql_command == SQLCOM_UPDATE ||
+       thd->lex->sql_command == SQLCOM_DELETE) &&
       !unit->first_select()->is_part_of_union() &&
       optimizer_flag(thd, OPTIMIZER_SWITCH_EXISTS_TO_IN) &&
       (is_top_level_item() ||

sql/sql_yacc.yy

@@ -13374,14 +13374,15 @@ delete_part2:
           {
             LEX *lex= Lex;
             lex->last_table()->vers_conditions= lex->vers_conditions;
-            lex->pop_select(); //main select
             lex->sql_command= SQLCOM_DELETE;
             if (!(lex->m_sql_cmd=
                   new (thd->mem_root) Sql_cmd_delete(false)))
               MYSQL_YYABORT;
             if (lex->check_main_unit_semantics())
               MYSQL_YYABORT;
           }
+          stmt_end
+          {}
         ;
 
 delete_single_table:
@@ -13432,14 +13433,14 @@ single_multi:
             LEX *lex= Lex;
             if ($3)
               Select->order_list= *($3);
-            lex->pop_select(); //main select
             lex->sql_command= SQLCOM_DELETE;
             if (!(lex->m_sql_cmd=
                   new (thd->mem_root) Sql_cmd_delete(false)))
               MYSQL_YYABORT;
             if (Lex->check_main_unit_semantics())
               MYSQL_YYABORT;
           }
+          stmt_end {}
         | table_alias_ref_list
           {
             LEX *lex= Lex;