Change the default @@optimizer_switch setting from

  semijoin=on,firstmatch=on,loosescan=on
to
  semijoin=off,firstmatch=off,loosescan=off
Adjust the testcases:
- Modify subselect*.test and join_cache.test so that all tests
  use the same execution paths as before (i.e. optimizations that
  are being tested are enabled)
- Let all other test files run with the new default settings (i.e.
  with new optimizations disabled)
- Copy subquery testcases from these files into t/subselect_extra.test
  which will run them with new optimizations enabled.

mysql-test/r/explain.result

@@ -199,16 +199,16 @@ insert into t2 values ('2001-01-01 1:1:1'), ('2001-01-01 1:1:1');
 flush tables;
 EXPLAIN SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN (SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.dt IS NULL );
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	OUTR	ALL	NULL	NULL	NULL	NULL	2	Using where; Start temporary
-1	PRIMARY	INNR	ALL	NULL	NULL	NULL	NULL	2	Using where; End temporary; Using join buffer (flat, BNL join)
+1	PRIMARY	OUTR	ALL	NULL	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	INNR	ALL	NULL	NULL	NULL	NULL	2	Using where
 flush tables;
 SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN (SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.dt IS NULL );
 dt
 flush tables;
 EXPLAIN SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN ( SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.t < '2005-11-13 7:41:31' );
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	OUTR	ALL	NULL	NULL	NULL	NULL	2	Using where; Start temporary
-1	PRIMARY	INNR	ALL	NULL	NULL	NULL	NULL	2	Using where; End temporary; Using join buffer (flat, BNL join)
+1	PRIMARY	OUTR	ALL	NULL	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	INNR	ALL	NULL	NULL	NULL	NULL	2	Using where
 flush tables;
 SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN ( SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.t < '2005-11-13 7:41:31' );
 dt

mysql-test/r/group_by.result

@@ -1542,8 +1542,8 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 EXPLAIN SELECT 1 FROM t1 WHERE a IN
 (SELECT a FROM t1 USE INDEX (i2) IGNORE INDEX (i2));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t1	index	PRIMARY,i2	PRIMARY	4	NULL	144	Using index
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	144	Using where; FirstMatch(t1)
+1	PRIMARY	t1	index	NULL	PRIMARY	4	NULL	144	Using where; Using index
+2	DEPENDENT SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	144	Using where
 CREATE TABLE t2 (a INT, b INT, KEY(a));
 INSERT INTO t2 VALUES (1, 1), (2, 2), (3,3), (4,4);
 EXPLAIN SELECT a, SUM(b) FROM t2 GROUP BY a LIMIT 2;
@@ -1555,8 +1555,8 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 EXPLAIN SELECT 1 FROM t2 WHERE a IN
 (SELECT a FROM t1 USE INDEX (i2) IGNORE INDEX (i2));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t2	index	a	a	5	NULL	4	Using index
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	144	Using where; FirstMatch(t2)
+1	PRIMARY	t2	index	NULL	a	5	NULL	4	Using where; Using index
+2	DEPENDENT SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	144	Using where
 SHOW VARIABLES LIKE 'old';
 Variable_name	Value
 old	OFF

mysql-test/r/group_min_max.result

@@ -1432,7 +1432,7 @@ group by a1,a2,b;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	range	NULL	idx_t1_1	147	NULL	17	Using where; Using index for group-by
 2	DEPENDENT SUBQUERY	t2	index	NULL	idx_t2_1	163	NULL	164	Using where; Using index
-2	DEPENDENT SUBQUERY	t3	index	NULL	idx_t3_1	10	NULL	192	Using where; Using index; FirstMatch(t2)
+3	DEPENDENT SUBQUERY	t3	index	NULL	idx_t3_1	10	NULL	192	Using where; Using index
 select a1,a2,b,c,min(c), max(c) from t1
 where exists ( select * from t2
 where t2.c in (select c from t3 where t3.c > t1.b) and
@@ -1489,7 +1489,7 @@ group by a1,a2,b;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	index	NULL	idx_t1_1	163	NULL	128	Using where; Using index
 2	DEPENDENT SUBQUERY	t2	index	NULL	idx_t2_1	163	NULL	164	Using where; Using index
-2	DEPENDENT SUBQUERY	t3	index	NULL	idx_t3_1	10	NULL	192	Using where; Using index; FirstMatch(t2)
+3	DEPENDENT SUBQUERY	t3	index	NULL	idx_t3_1	10	NULL	192	Using where; Using index
 select a1,a2,b,c,min(c), max(c) from t1
 where exists ( select * from t2
 where t2.c in (select c from t3 where t3.c > t1.c) and

mysql-test/r/join_cache.result

 DROP TABLE IF EXISTS t1,t2,t3,t4,t5,t6,t7,t8,t9,t10,t11;
 DROP DATABASE IF EXISTS world;
 set @save_optimizer_switch=@@optimizer_switch;
+set optimizer_switch='semijoin=on,firstmatch=on,loosescan=on';
 set @@optimizer_switch='semijoin_with_cache=on';
 set @@optimizer_switch='outer_join_with_cache=on';
 set names utf8;

mysql-test/r/subselect.result

 drop table if exists t1,t2,t3,t4,t5,t6,t7,t8,t11,t12;
 drop view if exists v2;
-set @save_optimizer_switch=@@optimizer_switch;
-set @@optimizer_switch="partial_match_rowid_merge=off,partial_match_table_scan=off";
+set @subselect_tmp=@@optimizer_switch;
+set @@optimizer_switch=ifnull(@optimizer_switch_for_subselect_test,
+"semijoin=on,firstmatch=on,loosescan=on,partial_match_rowid_merge=off,partial_match_table_scan=off");
 select (select 2);
 (select 2)
 2
@@ -4803,7 +4804,6 @@ SELECT 1 FROM t1 GROUP BY
 1
 1
 DROP TABLE t1;
-set @@optimizer_switch=@save_optimizer_switch;
 #
 # Bug #49512 : subquery with aggregate function crash 
 #   subselect_single_select_engine::exec()
@@ -5127,3 +5127,4 @@ ON t2.f10 = t3.f10
 f1
 DROP TABLE t1,t2,t3;
 End of 5.3 tests
+set optimizer_switch=@subselect_tmp;

mysql-test/r/subselect2.result

 drop table if exists t1, t2, t3, t4;
+set @subselect2_test_tmp=@@optimizer_switch;
+set optimizer_switch='semijoin=on,firstmatch=on';
 CREATE TABLE t1
 (
 DOCID VARCHAR(32)BINARY NOT NULL
@@ -144,3 +146,4 @@ and t2.a='1' AND t1.a=t3.b) > 0;
 a
 2
 DROP TABLE t1,t2,t3;
+set optimizer_switch=@subselect2_test_tmp;

mysql-test/r/subselect3.result

 drop table if exists t0, t1, t2, t3, t4, t5, t11, t12, t21, t22;
-set @save_optimizer_switch=@@optimizer_switch;
+set @subselect3_tmp= @@optimizer_switch;
+set optimizer_switch='semijoin=on,firstmatch=on,loosescan=on';
 create table t1 (oref int, grp int, ie int) ;
 insert into t1 (oref, grp, ie) values
 (1, 1, 1),
@@ -698,7 +699,6 @@ a	MAX(b)	test
 2	3	h
 3	4	i
 DROP TABLE t1, t2;
-set @save_optimizer_switch=@@optimizer_switch;
 set @@optimizer_switch="partial_match_rowid_merge=off,partial_match_table_scan=off";
 CREATE TABLE t1 (a int);
 CREATE TABLE t2 (b int, PRIMARY KEY(b));
@@ -1084,7 +1084,8 @@ a
 17
 18
 19
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@save_optimizer_switch;
+set @@optimizer_switch='materialization=off';
 explain select * from t1 where 2 in (select a from t0);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t0	ALL	NULL	NULL	NULL	NULL	11	Using where; FirstMatch
@@ -1399,7 +1400,7 @@ drop table t1,t2,t3;
 #
 # BUG#47367 Crash in Name_resolution_context::process_error
 #
-SET SESSION optimizer_switch = 'default,semijoin=off';
+SET SESSION optimizer_switch = 'semijoin=off';
 CREATE TABLE t1 (f1 INTEGER);
 CREATE TABLE t2 LIKE t1;
 CREATE PROCEDURE p1 () BEGIN SELECT f1 FROM t1 WHERE f1 IN (SELECT f1 FROM t2); END|
@@ -1421,4 +1422,4 @@ CALL p1;
 ERROR 42S22: Unknown column 'f1' in 'where clause'
 DROP PROCEDURE p1;
 DROP TABLE t1, t2;
-set @@optimizer_switch=@save_optimizer_switch;
+set @@optimizer_switch=@subselect3_tmp;

mysql-test/r/subselect3_jcl6.result

@@ -6,7 +6,8 @@ show variables like 'join_cache_level';
 Variable_name	Value
 join_cache_level	6
 drop table if exists t0, t1, t2, t3, t4, t5, t11, t12, t21, t22;
-set @save_optimizer_switch=@@optimizer_switch;
+set @subselect3_tmp= @@optimizer_switch;
+set optimizer_switch='semijoin=on,firstmatch=on,loosescan=on';
 create table t1 (oref int, grp int, ie int) ;
 insert into t1 (oref, grp, ie) values
 (1, 1, 1),
@@ -705,7 +706,6 @@ a	MAX(b)	test
 2	3	h
 3	4	i
 DROP TABLE t1, t2;
-set @save_optimizer_switch=@@optimizer_switch;
 set @@optimizer_switch="partial_match_rowid_merge=off,partial_match_table_scan=off";
 CREATE TABLE t1 (a int);
 CREATE TABLE t2 (b int, PRIMARY KEY(b));
@@ -1091,7 +1091,8 @@ a
 17
 18
 19
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@save_optimizer_switch;
+set @@optimizer_switch='materialization=off';
 explain select * from t1 where 2 in (select a from t0);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t0	ALL	NULL	NULL	NULL	NULL	11	Using where; FirstMatch
@@ -1406,7 +1407,7 @@ drop table t1,t2,t3;
 #
 # BUG#47367 Crash in Name_resolution_context::process_error
 #
-SET SESSION optimizer_switch = 'default,semijoin=off';
+SET SESSION optimizer_switch = 'semijoin=off';
 CREATE TABLE t1 (f1 INTEGER);
 CREATE TABLE t2 LIKE t1;
 CREATE PROCEDURE p1 () BEGIN SELECT f1 FROM t1 WHERE f1 IN (SELECT f1 FROM t2); END|
@@ -1428,7 +1429,7 @@ CALL p1;
 ERROR 42S22: Unknown column 'f1' in 'where clause'
 DROP PROCEDURE p1;
 DROP TABLE t1, t2;
-set @@optimizer_switch=@save_optimizer_switch;
+set @@optimizer_switch=@subselect3_tmp;
 set join_cache_level=default;
 show variables like 'join_cache_level';
 Variable_name	Value

mysql-test/r/subselect4.result

 drop table if exists t1,t2,t3,t4,t5,t6;
+set @subselect4_tmp= @@optimizer_switch;
+set optimizer_switch='semijoin=on,firstmatch=on,loosescan=on';
 #
 # Bug #46791: Assertion failed:(table->key_read==0),function unknown
 #    function,file sql_base.cc
@@ -1736,3 +1738,4 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 2	SUBQUERY	t3	ALL	NULL	NULL	NULL	NULL	2	
 3	SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	Using temporary
 drop table t1, t2, t3;
+set optimizer_switch=@subselect4_tmp;

mysql-test/r/subselect_mat.result

-set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
+set @subselect_mat_test_optimizer_switch_value='materialization=on,in_to_exists=off,semijoin=off';
+set @subselect_sj_mat_tmp= @@optimizer_switch;
+set optimizer_switch=ifnull(@subselect_mat_test_optimizer_switch_value, 'semijoin=on,firstmatch=on,loosescan=on');
+set @optimizer_switch_local_default= @@optimizer_switch;
 drop table if exists t1, t2, t3, t1i, t2i, t3i;
 drop table if exists columns;
 drop table if exists t1_16, t2_16, t3_16;
@@ -180,28 +183,34 @@ a1	a2
 select * from t1 where (a1, a2) in (select b1, min(b2) from t2i limit 1,1);
 ERROR 42000: This version of MySQL doesn't yet support 'LIMIT & IN/ALL/ANY/SOME subquery'
 set @save_optimizer_switch=@@optimizer_switch;
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='semijoin=off';
 prepare st1 from
 "select * from t1 where (a1, a2) in (select b1, min(b2) from t2 where b1 > '0' group by b1)";
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='materialization=off,in_to_exists=on';
 execute st1;
 a1	a2
 1 - 01	2 - 01
 1 - 02	2 - 02
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='semijoin=off';
 execute st1;
 a1	a2
 1 - 01	2 - 01
 1 - 02	2 - 02
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='materialization=off,in_to_exists=on';
 prepare st1 from
 "select * from t1 where (a1, a2) in (select b1, min(b2) from t2 where b1 > '0' group by b1)";
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='semijoin=off';
 execute st1;
 a1	a2
 1 - 01	2 - 01
 1 - 02	2 - 02
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='materialization=off,in_to_exists=on';
 execute st1;
 a1	a2
 1 - 01	2 - 01
@@ -1145,28 +1154,31 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 select min(a1) from t1 where 7 in (select b1 from t2 group by b1);
 min(a1)
 set @save_optimizer_switch=@@optimizer_switch;
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='materialization=off,in_to_exists=on';
 explain select min(a1) from t1 where 7 in (select b1 from t2 group by b1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
 2	DEPENDENT SUBQUERY	t2	system	NULL	NULL	NULL	NULL	0	const row not found
 select min(a1) from t1 where 7 in (select b1 from t2 group by b1);
 min(a1)
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='semijoin=off';
 explain select min(a1) from t1 where 7 in (select b1 from t2);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
-2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+2	SUBQUERY	t2	system	NULL	NULL	NULL	NULL	0	const row not found
 select min(a1) from t1 where 7 in (select b1 from t2);
 min(a1)
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='materialization=off,in_to_exists=on';
 # with MariaDB and MWL#90, this particular case is solved:
 explain select min(a1) from t1 where 7 in (select b1 from t2);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 select min(a1) from t1 where 7 in (select b1 from t2);
 min(a1)
-NULL
 # but when we go around MWL#90 code, the problem still shows up:
 explain select min(a1) from t1 where 7 in (select b1 from t2) or 2> 4;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
@@ -1199,7 +1211,8 @@ CREATE TABLE t2 LIKE t1;
 INSERT INTO t2 VALUES (1, 1.789);
 INSERT INTO t2 VALUES (13, 1.454);
 set @save_optimizer_switch=@@optimizer_switch;
-SET @@optimizer_switch='default,semijoin=on,materialization=on';
+set @@optimizer_switch=@optimizer_switch_local_default;
+SET @@optimizer_switch='semijoin=on,materialization=on';
 EXPLAIN SELECT COUNT(*) FROM t1 WHERE (f1,f2) IN (SELECT f1,f2 FROM t2);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	<subquery2>	ALL	distinct_key	NULL	NULL	NULL	2	
@@ -1222,7 +1235,8 @@ INSERT INTO t1 VALUES (1,'o','ffff','ffff','ffoo'),(2,'f','ffff','ffff','ffff');
 CREATE TABLE t2 LIKE t1;
 INSERT INTO t2 VALUES (1,'i','iiii','iiii','iiii'),(2,'f','ffff','ffff','ffff');
 set @save_optimizer_switch=@@optimizer_switch;
-SET @@optimizer_switch='default,semijoin=on,materialization=on';
+set @@optimizer_switch=@optimizer_switch_local_default;
+SET @@optimizer_switch='semijoin=on,materialization=on';
 EXPLAIN SELECT pk FROM t1 WHERE (a) IN (SELECT a FROM t2 WHERE pk > 0);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
@@ -1320,6 +1334,8 @@ select left(a1,7), left(a2,7) from t1_1024 where (a1,3) in (select substring(b1,
 left(a1,7)	left(a2,7)
 1 - 01x	2 - 01x
 drop table t1_1024, t2_1024;
+set optimizer_switch=@subselect_sj_mat_tmp;
+set @subselect_mat_test_optimizer_switch_value=null;
 set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
 create table t0 (a int);
 insert into t0 values (0),(1),(2);

mysql-test/r/subselect_no_mat.result

@@ -4,8 +4,9 @@ select @@optimizer_switch like '%materialization=on%';
 set optimizer_switch='materialization=off';
 drop table if exists t1,t2,t3,t4,t5,t6,t7,t8,t11,t12;
 drop view if exists v2;
-set @save_optimizer_switch=@@optimizer_switch;
-set @@optimizer_switch="partial_match_rowid_merge=off,partial_match_table_scan=off";
+set @subselect_tmp=@@optimizer_switch;
+set @@optimizer_switch=ifnull(@optimizer_switch_for_subselect_test,
+"semijoin=on,firstmatch=on,loosescan=on,partial_match_rowid_merge=off,partial_match_table_scan=off");
 select (select 2);
 (select 2)
 2
@@ -4807,7 +4808,6 @@ SELECT 1 FROM t1 GROUP BY
 1
 1
 DROP TABLE t1;
-set @@optimizer_switch=@save_optimizer_switch;
 #
 # Bug #49512 : subquery with aggregate function crash 
 #   subselect_single_select_engine::exec()
@@ -5131,6 +5131,7 @@ ON t2.f10 = t3.f10
 f1
 DROP TABLE t1,t2,t3;
 End of 5.3 tests
+set optimizer_switch=@subselect_tmp;
 set optimizer_switch=default;
 select @@optimizer_switch like '%materialization=on%';
 @@optimizer_switch like '%materialization=on%'

mysql-test/r/subselect_no_opts.result

-set optimizer_switch='materialization=off,semijoin=off';
+set @optimizer_switch_for_subselect_test='materialization=off,semijoin=off';
 drop table if exists t1,t2,t3,t4,t5,t6,t7,t8,t11,t12;
 drop view if exists v2;
-set @save_optimizer_switch=@@optimizer_switch;
-set @@optimizer_switch="partial_match_rowid_merge=off,partial_match_table_scan=off";
+set @subselect_tmp=@@optimizer_switch;
+set @@optimizer_switch=ifnull(@optimizer_switch_for_subselect_test,
+"semijoin=on,firstmatch=on,loosescan=on,partial_match_rowid_merge=off,partial_match_table_scan=off");
 select (select 2);
 (select 2)
 2
@@ -4804,7 +4805,6 @@ SELECT 1 FROM t1 GROUP BY
 1
 1
 DROP TABLE t1;
-set @@optimizer_switch=@save_optimizer_switch;
 #
 # Bug #49512 : subquery with aggregate function crash 
 #   subselect_single_select_engine::exec()
@@ -5128,4 +5128,5 @@ ON t2.f10 = t3.f10
 f1
 DROP TABLE t1,t2,t3;
 End of 5.3 tests
-set optimizer_switch=default;
+set optimizer_switch=@subselect_tmp;
+set @optimizer_switch_for_subselect_test=null;

mysql-test/r/subselect_no_semijoin.result

-set optimizer_switch='semijoin=off';
+set @optimizer_switch_for_subselect_test='semijoin=off';
 drop table if exists t1,t2,t3,t4,t5,t6,t7,t8,t11,t12;
 drop view if exists v2;
-set @save_optimizer_switch=@@optimizer_switch;
-set @@optimizer_switch="partial_match_rowid_merge=off,partial_match_table_scan=off";
+set @subselect_tmp=@@optimizer_switch;
+set @@optimizer_switch=ifnull(@optimizer_switch_for_subselect_test,
+"semijoin=on,firstmatch=on,loosescan=on,partial_match_rowid_merge=off,partial_match_table_scan=off");
 select (select 2);
 (select 2)
 2
@@ -4804,7 +4805,6 @@ SELECT 1 FROM t1 GROUP BY
 1
 1
 DROP TABLE t1;
-set @@optimizer_switch=@save_optimizer_switch;
 #
 # Bug #49512 : subquery with aggregate function crash 
 #   subselect_single_select_engine::exec()
@@ -5128,4 +5128,5 @@ ON t2.f10 = t3.f10
 f1
 DROP TABLE t1,t2,t3;
 End of 5.3 tests
-set optimizer_switch=default;
+set optimizer_switch=@subselect_tmp;
+set @optimizer_switch_for_subselect_test=null;

mysql-test/r/subselect_sj.result

 drop table if exists t0, t1, t2, t3, t4, t10, t11, t12;
 drop view if exists v1, v2;
 drop procedure if exists p1;
+set @subselect_sj_tmp= @@optimizer_switch;
+set optimizer_switch='semijoin=on,firstmatch=on,loosescan=on';
 set @save_optimizer_switch=@@optimizer_switch;
 create table t0 (a int);
 insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
@@ -1536,4 +1538,4 @@ AND t1.f1 = t2.f1 ;
 f1	f1
 DROP TABLE t1, t2;
 set optimizer_switch=@save_802965;
-set @@optimizer_switch=@save_optimizer_switch;
+set optimizer_switch=@subselect_sj_tmp;

mysql-test/r/subselect_sj2.result

+set @subselect_sj2_tmp= @@optimizer_switch;
+set optimizer_switch='semijoin=on,firstmatch=on,loosescan=on';
 drop table if exists t0, t1, t2, t3;
 drop view if exists v1;
 create table t0 (a int);
@@ -744,3 +746,4 @@ LEFT JOIN t2 AS SQ4_alias3 ON SQ4_alias3.f10
 GROUP BY field2;
 field2
 drop table t1, t2, t3;
+set optimizer_switch=@subselect_sj2_tmp;

mysql-test/r/subselect_sj2_jcl6.result

@@ -5,6 +5,8 @@ set join_cache_level=6;
 show variables like 'join_cache_level';
 Variable_name	Value
 join_cache_level	6
+set @subselect_sj2_tmp= @@optimizer_switch;
+set optimizer_switch='semijoin=on,firstmatch=on,loosescan=on';
 drop table if exists t0, t1, t2, t3;
 drop view if exists v1;
 create table t0 (a int);
@@ -753,6 +755,7 @@ LEFT JOIN t2 AS SQ4_alias3 ON SQ4_alias3.f10
 GROUP BY field2;
 field2
 drop table t1, t2, t3;
+set optimizer_switch=@subselect_sj2_tmp;
 set join_cache_level=default;
 show variables like 'join_cache_level';
 Variable_name	Value

mysql-test/r/subselect_sj2_mat.result

 set optimizer_switch='materialization=on';
+set @subselect_sj2_tmp= @@optimizer_switch;
+set optimizer_switch='semijoin=on,firstmatch=on,loosescan=on';
 drop table if exists t0, t1, t2, t3;
 drop view if exists v1;
 create table t0 (a int);
@@ -755,6 +757,7 @@ LEFT JOIN t2 AS SQ4_alias3 ON SQ4_alias3.f10
 GROUP BY field2;
 field2
 drop table t1, t2, t3;
+set optimizer_switch=@subselect_sj2_tmp;
 set optimizer_switch=default;
 select @@optimizer_switch like '%materialization=on%';
 @@optimizer_switch like '%materialization=on%'

mysql-test/r/subselect_sj_jcl6.result

 set @save_optimizer_switch_jcl6=@@optimizer_switch;
+set @@optimizer_switch='semijoin=on,firstmatch=on,loosescan=on';
 set @@optimizer_switch='semijoin_with_cache=on';
 set @@optimizer_switch='outer_join_with_cache=on';
 set @@optimizer_switch='join_cache_hashed=off';
@@ -9,6 +10,8 @@ join_cache_level	6
 drop table if exists t0, t1, t2, t3, t4, t10, t11, t12;
 drop view if exists v1, v2;
 drop procedure if exists p1;
+set @subselect_sj_tmp= @@optimizer_switch;
+set optimizer_switch='semijoin=on,firstmatch=on,loosescan=on';
 set @save_optimizer_switch=@@optimizer_switch;
 create table t0 (a int);
 insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
@@ -1544,7 +1547,7 @@ AND t1.f1 = t2.f1 ;
 f1	f1
 DROP TABLE t1, t2;
 set optimizer_switch=@save_802965;
-set @@optimizer_switch=@save_optimizer_switch;
+set optimizer_switch=@subselect_sj_tmp;
 #
 # BUG#49129: Wrong result with IN-subquery with join_cache_level=6 and firstmatch=off
 #

mysql-test/r/subselect_sj_mat.result

+set @subselect_sj_mat_tmp= @@optimizer_switch;
+set optimizer_switch=ifnull(@subselect_mat_test_optimizer_switch_value, 'semijoin=on,firstmatch=on,loosescan=on');
+set @optimizer_switch_local_default= @@optimizer_switch;
 drop table if exists t1, t2, t3, t1i, t2i, t3i;
 drop table if exists columns;
 drop table if exists t1_16, t2_16, t3_16;
@@ -190,28 +193,34 @@ a1	a2
 select * from t1 where (a1, a2) in (select b1, min(b2) from t2i limit 1,1);
 ERROR 42000: This version of MySQL doesn't yet support 'LIMIT & IN/ALL/ANY/SOME subquery'
 set @save_optimizer_switch=@@optimizer_switch;
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='semijoin=off';
 prepare st1 from
 "select * from t1 where (a1, a2) in (select b1, min(b2) from t2 where b1 > '0' group by b1)";
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='materialization=off,in_to_exists=on';
 execute st1;
 a1	a2
 1 - 01	2 - 01
 1 - 02	2 - 02
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='semijoin=off';
 execute st1;
 a1	a2
 1 - 01	2 - 01
 1 - 02	2 - 02
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='materialization=off,in_to_exists=on';
 prepare st1 from
 "select * from t1 where (a1, a2) in (select b1, min(b2) from t2 where b1 > '0' group by b1)";
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='semijoin=off';
 execute st1;
 a1	a2
 1 - 01	2 - 01
 1 - 02	2 - 02
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='materialization=off,in_to_exists=on';
 execute st1;
 a1	a2
 1 - 01	2 - 01
@@ -1182,21 +1191,24 @@ select min(a1) from t1 where 7 in (select b1 from t2 group by b1);
 min(a1)
 NULL
 set @save_optimizer_switch=@@optimizer_switch;
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='materialization=off,in_to_exists=on';
 explain select min(a1) from t1 where 7 in (select b1 from t2 group by b1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
 2	DEPENDENT SUBQUERY	t2	system	NULL	NULL	NULL	NULL	0	const row not found
 select min(a1) from t1 where 7 in (select b1 from t2 group by b1);
 min(a1)
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='semijoin=off';
 explain select min(a1) from t1 where 7 in (select b1 from t2);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
 2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 select min(a1) from t1 where 7 in (select b1 from t2);
 min(a1)
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='materialization=off,in_to_exists=on';
 # with MariaDB and MWL#90, this particular case is solved:
 explain select min(a1) from t1 where 7 in (select b1 from t2);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
@@ -1237,7 +1249,8 @@ CREATE TABLE t2 LIKE t1;
 INSERT INTO t2 VALUES (1, 1.789);
 INSERT INTO t2 VALUES (13, 1.454);
 set @save_optimizer_switch=@@optimizer_switch;
-SET @@optimizer_switch='default,semijoin=on,materialization=on';
+set @@optimizer_switch=@optimizer_switch_local_default;
+SET @@optimizer_switch='semijoin=on,materialization=on';
 EXPLAIN SELECT COUNT(*) FROM t1 WHERE (f1,f2) IN (SELECT f1,f2 FROM t2);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	<subquery2>	ALL	distinct_key	NULL	NULL	NULL	2	
@@ -1260,7 +1273,8 @@ INSERT INTO t1 VALUES (1,'o','ffff','ffff','ffoo'),(2,'f','ffff','ffff','ffff');
 CREATE TABLE t2 LIKE t1;
 INSERT INTO t2 VALUES (1,'i','iiii','iiii','iiii'),(2,'f','ffff','ffff','ffff');
 set @save_optimizer_switch=@@optimizer_switch;
-SET @@optimizer_switch='default,semijoin=on,materialization=on';
+set @@optimizer_switch=@optimizer_switch_local_default;
+SET @@optimizer_switch='semijoin=on,materialization=on';
 EXPLAIN SELECT pk FROM t1 WHERE (a) IN (SELECT a FROM t2 WHERE pk > 0);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
@@ -1358,3 +1372,4 @@ select left(a1,7), left(a2,7) from t1_1024 where (a1,3) in (select substring(b1,
 left(a1,7)	left(a2,7)
 1 - 01x	2 - 01x
 drop table t1_1024, t2_1024;
+set optimizer_switch=@subselect_sj_mat_tmp;

mysql-test/r/subselect_sj_nonmerged.result

 drop table if exists t0, t1, t2, t3, t4;
 set @save_optimizer_switch=@@optimizer_switch;
-set optimizer_switch='materialization=on';
+set optimizer_switch='semijoin=on,materialization=on';
 create table t0 (a int);
 insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
 create table t1 as select * from t0;

mysql-test/r/type_datetime.result

@@ -514,10 +514,11 @@ explain extended
 select * from t1
 where id in (select id from t1 as x1 where (t1.cur_date is null));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	PRIMARY	t1	system	NULL	NULL	NULL	NULL	1	100.00	
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 Warnings:
 Note	1276	Field or reference 'test.t1.cur_date' of SELECT #2 was resolved in SELECT #1
-Note	1003	select 1 AS `id`,'2007-04-25 18:30:22' AS `cur_date` from `test`.`t1` semi join (`test`.`t1` `x1`) where (('2007-04-25 18:30:22' = 0))
+Note	1003	select 1 AS `id`,'2007-04-25 18:30:22' AS `cur_date` from `test`.`t1` where <expr_cache><1,'2007-04-25 18:30:22'>(<in_optimizer>(1,<exists>(select `test`.`x1`.`id` from `test`.`t1` `x1` where 0)))
 select * from t1
 where id in (select id from t1 as x1 where (t1.cur_date is null));
 id	cur_date
@@ -525,10 +526,11 @@ explain extended
 select * from t2
 where id in (select id from t2 as x1 where (t2.cur_date is null));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+1	PRIMARY	t2	system	NULL	NULL	NULL	NULL	1	100.00	
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 Warnings:
 Note	1276	Field or reference 'test.t2.cur_date' of SELECT #2 was resolved in SELECT #1
-Note	1003	select 1 AS `id`,'2007-04-25' AS `cur_date` from `test`.`t2` semi join (`test`.`t2` `x1`) where (('2007-04-25' = 0))
+Note	1003	select 1 AS `id`,'2007-04-25' AS `cur_date` from `test`.`t2` where <expr_cache><1,'2007-04-25'>(<in_optimizer>(1,<exists>(select `test`.`x1`.`id` from `test`.`t2` `x1` where 0)))
 select * from t2
 where id in (select id from t2 as x1 where (t2.cur_date is null));
 id	cur_date
@@ -538,11 +540,11 @@ explain extended
 select * from t1
 where id in (select id from t1 as x1 where (t1.cur_date is null));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where; Start temporary
-1	PRIMARY	x1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where; End temporary; Using join buffer (flat, BNL join)
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+2	DEPENDENT SUBQUERY	x1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
 Warnings:
 Note	1276	Field or reference 'test.t1.cur_date' of SELECT #2 was resolved in SELECT #1
-Note	1003	select `test`.`t1`.`id` AS `id`,`test`.`t1`.`cur_date` AS `cur_date` from `test`.`t1` semi join (`test`.`t1` `x1`) where ((`test`.`x1`.`id` = `test`.`t1`.`id`) and (`test`.`t1`.`cur_date` = 0))
+Note	1003	select `test`.`t1`.`id` AS `id`,`test`.`t1`.`cur_date` AS `cur_date` from `test`.`t1` where <expr_cache><`test`.`t1`.`id`,`test`.`t1`.`cur_date`>(<in_optimizer>(`test`.`t1`.`id`,<exists>(select `test`.`x1`.`id` from `test`.`t1` `x1` where ((`test`.`t1`.`cur_date` = 0) and (<cache>(`test`.`t1`.`id`) = `test`.`x1`.`id`)))))
 select * from t1
 where id in (select id from t1 as x1 where (t1.cur_date is null));
 id	cur_date
@@ -550,11 +552,11 @@ explain extended
 select * from t2
 where id in (select id from t2 as x1 where (t2.cur_date is null));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where; Start temporary
-1	PRIMARY	x1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where; End temporary; Using join buffer (flat, BNL join)
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+2	DEPENDENT SUBQUERY	x1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
 Warnings:
 Note	1276	Field or reference 'test.t2.cur_date' of SELECT #2 was resolved in SELECT #1
-Note	1003	select `test`.`t2`.`id` AS `id`,`test`.`t2`.`cur_date` AS `cur_date` from `test`.`t2` semi join (`test`.`t2` `x1`) where ((`test`.`x1`.`id` = `test`.`t2`.`id`) and (`test`.`t2`.`cur_date` = 0))
+Note	1003	select `test`.`t2`.`id` AS `id`,`test`.`t2`.`cur_date` AS `cur_date` from `test`.`t2` where <expr_cache><`test`.`t2`.`id`,`test`.`t2`.`cur_date`>(<in_optimizer>(`test`.`t2`.`id`,<exists>(select `test`.`x1`.`id` from `test`.`t2` `x1` where ((`test`.`t2`.`cur_date` = 0) and (<cache>(`test`.`t2`.`id`) = `test`.`x1`.`id`)))))
 select * from t2
 where id in (select id from t2 as x1 where (t2.cur_date is null));
 id	cur_date

mysql-test/suite/vcol/r/vcol_select_innodb.result

@@ -63,8 +63,8 @@ a	b	c
 3	-3	-3
 explain select * from t1 where b in (select c from t3);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t3	index	c	c	5	NULL	3	Using index
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	5	Using where; Using join buffer (flat, BNL join)
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	5	Using where
+2	DEPENDENT SUBQUERY	t3	index_subquery	c	c	5	func	1	Using index
 # select_type=PRIMARY, type=range,ref
 select * from t1 where c in (select c from t3 where c between -2 and -1);
 a	b	c
@@ -73,8 +73,8 @@ a	b	c
 1	-1	-1
 explain select * from t1 where c in (select c from t3 where c between -2 and -1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t3	index	c	c	5	NULL	3	Using where; Using index
-1	PRIMARY	t1	ref	c	c	5	test.t3.c	1	
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	5	Using where
+2	DEPENDENT SUBQUERY	t3	index_subquery	c	c	5	func	1	Using index; Using where
 # select_type=UNION, type=system
 # select_type=UNION RESULT, type=<union1,2>
 select * from t1 union select * from t2;

mysql-test/suite/vcol/r/vcol_select_myisam.result

@@ -63,8 +63,8 @@ a	b	c
 3	-3	-3
 explain select * from t1 where b in (select c from t3);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t3	index	c	c	5	NULL	3	Using index
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	5	Using where; Using join buffer (flat, BNL join)
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	5	Using where
+2	DEPENDENT SUBQUERY	t3	index_subquery	c	c	5	func	2	Using index
 # select_type=PRIMARY, type=range,ref
 select * from t1 where c in (select c from t3 where c between -2 and -1);
 a	b	c
@@ -73,8 +73,8 @@ a	b	c
 1	-1	-1
 explain select * from t1 where c in (select c from t3 where c between -2 and -1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t3	index	c	c	5	NULL	3	Using where; Using index
-1	PRIMARY	t1	ref	c	c	5	test.t3.c	2	
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	5	Using where
+2	DEPENDENT SUBQUERY	t3	index_subquery	c	c	5	func	2	Using index; Using where
 # select_type=UNION, type=system
 # select_type=UNION RESULT, type=<union1,2>
 select * from t1 union select * from t2;

mysql-test/t/join_cache.test

@@ -4,6 +4,7 @@ DROP DATABASE IF EXISTS world;
 --enable_warnings
 
 set @save_optimizer_switch=@@optimizer_switch;
+set optimizer_switch='semijoin=on,firstmatch=on,loosescan=on';
 set @@optimizer_switch='semijoin_with_cache=on';
 set @@optimizer_switch='outer_join_with_cache=on';
 

mysql-test/t/subselect.test

@@ -12,8 +12,9 @@ drop table if exists t1,t2,t3,t4,t5,t6,t7,t8,t11,t12;
 drop view if exists v2;
 --enable_warnings
 
-set @save_optimizer_switch=@@optimizer_switch;
-set @@optimizer_switch="partial_match_rowid_merge=off,partial_match_table_scan=off";
+set @subselect_tmp=@@optimizer_switch;
+set @@optimizer_switch=ifnull(@optimizer_switch_for_subselect_test,
+                              "semijoin=on,firstmatch=on,loosescan=on,partial_match_rowid_merge=off,partial_match_table_scan=off");
 
 select (select 2);
 explain extended select (select 2);
@@ -4066,7 +4067,7 @@ SELECT 1 FROM t1 GROUP BY
   (SELECT LAST_INSERT_ID() FROM t1 ORDER BY MIN(a) ASC LIMIT 1);
 DROP TABLE t1;
 
-set @@optimizer_switch=@save_optimizer_switch;
+#Seems to be not needed here: set @@optimizer_switch=@subselect_tmp;
 --echo #
 --echo # Bug #49512 : subquery with aggregate function crash 
 --echo #   subselect_single_select_engine::exec()
@@ -4402,3 +4403,4 @@ WHERE
 DROP TABLE t1,t2,t3;
 
 --echo End of 5.3 tests
+set optimizer_switch=@subselect_tmp;

mysql-test/t/subselect2.test

@@ -8,6 +8,9 @@
 drop table if exists t1, t2, t3, t4;
 --enable_warnings
 
+set @subselect2_test_tmp=@@optimizer_switch;
+set optimizer_switch='semijoin=on,firstmatch=on';
+
 CREATE TABLE t1
 (
 DOCID VARCHAR(32)BINARY NOT NULL
@@ -168,3 +171,6 @@ SELECT t1.* FROM t1 WHERE (SELECT COUNT(*) FROM t3,t2 WHERE t3.c=t2.a
                            and t2.a='1' AND t1.a=t3.b) > 0;
 
 DROP TABLE t1,t2,t3;
+
+set optimizer_switch=@subselect2_test_tmp;
+

mysql-test/t/subselect3.test

@@ -2,7 +2,8 @@
 drop table if exists t0, t1, t2, t3, t4, t5, t11, t12, t21, t22;
 --enable_warnings
 
-set @save_optimizer_switch=@@optimizer_switch;
+set @subselect3_tmp= @@optimizer_switch;
+set optimizer_switch='semijoin=on,firstmatch=on,loosescan=on';
 
 #
 # 1. Subquery with GROUP/HAVING
@@ -538,7 +539,6 @@ SELECT a, MAX(b),
 DROP TABLE t1, t2;
 
 # The next three test cases must be executed with the IN=>EXISTS strategy
-set @save_optimizer_switch=@@optimizer_switch;
 set @@optimizer_switch="partial_match_rowid_merge=off,partial_match_table_scan=off";
 
 #
@@ -906,7 +906,8 @@ set @@optimizer_switch='firstmatch=off,materialization=off';
 insert into t0 values(2);
 explain select * from t1 where 2 in (select a from t0);
 select * from t1 where 2 in (select a from t0);
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@save_optimizer_switch;
+set @@optimizer_switch='materialization=off';
 explain select * from t1 where 2 in (select a from t0);
 select * from t1 where 2 in (select a from t0);
 set @@optimizer_switch=@save_optimizer_switch;
@@ -1160,7 +1161,7 @@ drop table t1,t2,t3;
 --echo # BUG#47367 Crash in Name_resolution_context::process_error
 --echo #
 
-SET SESSION optimizer_switch = 'default,semijoin=off';
+SET SESSION optimizer_switch = 'semijoin=off';
 CREATE TABLE t1 (f1 INTEGER);
 CREATE TABLE t2 LIKE t1;
 delimiter |;
@@ -1186,4 +1187,4 @@ DROP PROCEDURE p1;
 DROP TABLE t1, t2;
 
 # The following command must be the last one the file 
-set @@optimizer_switch=@save_optimizer_switch;
+set @@optimizer_switch=@subselect3_tmp;

mysql-test/t/subselect4.test

@@ -4,6 +4,9 @@
 drop table if exists t1,t2,t3,t4,t5,t6;
 --enable_warnings
 
+set @subselect4_tmp= @@optimizer_switch;
+set optimizer_switch='semijoin=on,firstmatch=on,loosescan=on';
+
 --echo #
 --echo # Bug #46791: Assertion failed:(table->key_read==0),function unknown
 --echo #    function,file sql_base.cc
@@ -1415,3 +1418,5 @@ WHERE t2.f1 = (
                 FROM t1));
 
 drop table t1, t2, t3;
+
+set optimizer_switch=@subselect4_tmp;

mysql-test/t/subselect_mat.test

@@ -5,9 +5,11 @@
 
 
 # force the use of materialization
-set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
+set @subselect_mat_test_optimizer_switch_value='materialization=on,in_to_exists=off,semijoin=off';
 
 --source t/subselect_sj_mat.test
+set @subselect_mat_test_optimizer_switch_value=null;
+
 set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
 #
 # Test that the contents of the temp table of a materialized subquery is

mysql-test/t/subselect_no_opts.test

 # 
 # Run subselect.test without semi-join and materialization optimizations
 #  (test in-to-exists)
-set optimizer_switch='materialization=off,semijoin=off';
 
+set @optimizer_switch_for_subselect_test='materialization=off,semijoin=off'; 
 --source t/subselect.test
 
-set optimizer_switch=default;
+set @optimizer_switch_for_subselect_test=null; 
 

mysql-test/t/subselect_no_semijoin.test

 # 
 # Run subselect.test without semi-join optimization (test materialize)
 #
-set optimizer_switch='semijoin=off';
+set @optimizer_switch_for_subselect_test='semijoin=off'; 
 
 --source t/subselect.test
 
-set optimizer_switch=default;
+set @optimizer_switch_for_subselect_test=null; 

mysql-test/t/subselect_sj.test

@@ -7,6 +7,9 @@ drop view if exists v1, v2;
 drop procedure if exists p1;
 --enable_warnings
 
+set @subselect_sj_tmp= @@optimizer_switch;
+set optimizer_switch='semijoin=on,firstmatch=on,loosescan=on';
+# The 'default' value within the scope of this test:
 set @save_optimizer_switch=@@optimizer_switch;
 
 #
@@ -1396,4 +1399,4 @@ DROP TABLE t1, t2;
 set optimizer_switch=@save_802965;
 
 # The following command must be the last one the file 
-set @@optimizer_switch=@save_optimizer_switch;
+set optimizer_switch=@subselect_sj_tmp;

mysql-test/t/subselect_sj2.test

@@ -2,6 +2,9 @@
 # DuplicateElimination strategy test
 #
 --source include/have_innodb.inc
+
+set @subselect_sj2_tmp= @@optimizer_switch;
+set optimizer_switch='semijoin=on,firstmatch=on,loosescan=on';
 --disable_warnings
 drop table if exists t0, t1, t2, t3;
 drop view if exists v1;
@@ -939,3 +942,5 @@ WHERE alias2.f11 IN (
 )
 GROUP BY field2;
 drop table t1, t2, t3;
+
+set optimizer_switch=@subselect_sj2_tmp;

mysql-test/t/subselect_sj_jcl6.test

@@ -3,6 +3,7 @@
 #
 
 set @save_optimizer_switch_jcl6=@@optimizer_switch;
+set @@optimizer_switch='semijoin=on,firstmatch=on,loosescan=on';
 set @@optimizer_switch='semijoin_with_cache=on';
 set @@optimizer_switch='outer_join_with_cache=on';
 set @@optimizer_switch='join_cache_hashed=off';

mysql-test/t/subselect_sj_mat.test

@@ -3,6 +3,10 @@
 # (WL#1110: Subquery optimization: materialization)
 #
 
+set @subselect_sj_mat_tmp= @@optimizer_switch;
+set optimizer_switch=ifnull(@subselect_mat_test_optimizer_switch_value, 'semijoin=on,firstmatch=on,loosescan=on');
+set @optimizer_switch_local_default= @@optimizer_switch;
+
 --disable_warnings
 drop table if exists t1, t2, t3, t1i, t2i, t3i;
 drop table if exists columns;
@@ -121,20 +125,26 @@ select * from t1 where (a1, a2) in (select b1, min(b2) from t2i limit 1,1);
 # test re-optimization/re-execution with different execution methods
 # prepare once, exec with different modes
 set @save_optimizer_switch=@@optimizer_switch;
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='semijoin=off';
 prepare st1 from
 "select * from t1 where (a1, a2) in (select b1, min(b2) from t2 where b1 > '0' group by b1)";
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='materialization=off,in_to_exists=on';
 execute st1;
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='semijoin=off';
 execute st1;
 
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='materialization=off,in_to_exists=on';
 prepare st1 from
 "select * from t1 where (a1, a2) in (select b1, min(b2) from t2 where b1 > '0' group by b1)";
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='semijoin=off';
 execute st1;
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='materialization=off,in_to_exists=on';
 execute st1;
 set @@optimizer_switch=@save_optimizer_switch;
 
@@ -826,18 +836,21 @@ explain select min(a1) from t1 where 7 in (select b1 from t2 group by b1);
 select min(a1) from t1 where 7 in (select b1 from t2 group by b1);
 # Query with group by, executed via IN=>EXISTS
 set @save_optimizer_switch=@@optimizer_switch;
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='materialization=off,in_to_exists=on';
 explain select min(a1) from t1 where 7 in (select b1 from t2 group by b1);
 select min(a1) from t1 where 7 in (select b1 from t2 group by b1);
 
 # Executed with materialization
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='semijoin=off';
 explain select min(a1) from t1 where 7 in (select b1 from t2);
 select min(a1) from t1 where 7 in (select b1 from t2);
 # Executed with semi-join. Notice, this time we get a different result (NULL).
 # This is the only correct result of all four queries. This difference is
 # filed as BUG#40037.
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch=@optimizer_switch_local_default;
+set @@optimizer_switch='materialization=off,in_to_exists=on';
 -- echo # with MariaDB and MWL#90, this particular case is solved:
 explain select min(a1) from t1 where 7 in (select b1 from t2);
 select min(a1) from t1 where 7 in (select b1 from t2);
@@ -875,7 +888,8 @@ INSERT INTO t2 VALUES (1, 1.789);
 INSERT INTO t2 VALUES (13, 1.454);
 
 set @save_optimizer_switch=@@optimizer_switch;
-SET @@optimizer_switch='default,semijoin=on,materialization=on';
+set @@optimizer_switch=@optimizer_switch_local_default;
+SET @@optimizer_switch='semijoin=on,materialization=on';
 EXPLAIN SELECT COUNT(*) FROM t1 WHERE (f1,f2) IN (SELECT f1,f2 FROM t2);
 SELECT COUNT(*) FROM t1 WHERE (f1,f2) IN (SELECT f1,f2 FROM t2);
 set @@optimizer_switch= @save_optimizer_switch;
@@ -899,7 +913,8 @@ CREATE TABLE t2 LIKE t1;
 INSERT INTO t2 VALUES (1,'i','iiii','iiii','iiii'),(2,'f','ffff','ffff','ffff');
 
 set @save_optimizer_switch=@@optimizer_switch;
-SET @@optimizer_switch='default,semijoin=on,materialization=on';
+set @@optimizer_switch=@optimizer_switch_local_default;
+SET @@optimizer_switch='semijoin=on,materialization=on';
 EXPLAIN SELECT pk FROM t1 WHERE (a) IN (SELECT a FROM t2 WHERE pk > 0);
 SELECT pk FROM t1 WHERE (a) IN (SELECT a FROM t2 WHERE pk > 0);
 SELECT pk FROM t1 WHERE (b,c,d) IN (SELECT b,c,d FROM t2 WHERE pk > 0);
@@ -972,3 +987,6 @@ explain select left(a1,7), left(a2,7) from t1_1024 where (a1,3) in (select subst
 select left(a1,7), left(a2,7) from t1_1024 where (a1,3) in (select substring(b1,1,1024), count(*) from t2_1024 where b1 > '0');
 
 drop table t1_1024, t2_1024;
+
+set optimizer_switch=@subselect_sj_mat_tmp;
+

mysql-test/t/subselect_sj_nonmerged.test

@@ -6,7 +6,7 @@ drop table if exists t0, t1, t2, t3, t4;
 --enable_warnings
 
 set @save_optimizer_switch=@@optimizer_switch;
-set optimizer_switch='materialization=on';
+set optimizer_switch='semijoin=on,materialization=on';
 
 create table t0 (a int);
 insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);

sql/mysql_priv.h

@@ -615,10 +615,7 @@ enabled by default, add OPTIMIZER_SWITCH_MATERIALIZATION
                                     OPTIMIZER_SWITCH_INDEX_COND_PUSHDOWN | \
                                     OPTIMIZER_SWITCH_DERIVED_MERGE | \
                                     OPTIMIZER_SWITCH_DERIVED_WITH_KEYS | \
-                                    OPTIMIZER_SWITCH_FIRSTMATCH | \
-                                    OPTIMIZER_SWITCH_LOOSE_SCAN | \
                                     OPTIMIZER_SWITCH_IN_TO_EXISTS | \
-                                    OPTIMIZER_SWITCH_SEMIJOIN | \
                                     OPTIMIZER_SWITCH_PARTIAL_MATCH_ROWID_MERGE|\
                                     OPTIMIZER_SWITCH_PARTIAL_MATCH_TABLE_SCAN|\
                                     OPTIMIZER_SWITCH_SUBQUERY_CACHE|\
@@ -638,10 +635,7 @@ enabled by default, add OPTIMIZER_SWITCH_MATERIALIZATION
                                     OPTIMIZER_SWITCH_DERIVED_MERGE | \
                                     OPTIMIZER_SWITCH_DERIVED_WITH_KEYS | \
                                     OPTIMIZER_SWITCH_TABLE_ELIMINATION | \
-                                    OPTIMIZER_SWITCH_FIRSTMATCH | \
-                                    OPTIMIZER_SWITCH_LOOSE_SCAN | \
                                     OPTIMIZER_SWITCH_IN_TO_EXISTS | \
-                                    OPTIMIZER_SWITCH_SEMIJOIN | \
                                     OPTIMIZER_SWITCH_PARTIAL_MATCH_ROWID_MERGE|\
                                     OPTIMIZER_SWITCH_PARTIAL_MATCH_TABLE_SCAN|\
                                     OPTIMIZER_SWITCH_SUBQUERY_CACHE|\

sql/mysqld.cc

@@ -488,11 +488,11 @@ static const char *optimizer_switch_str="index_merge=on,index_merge_union=on,"
                                         "index_condition_pushdown=on,"
                                         "derived_merge=on,"
                                         "derived_with_keys=on,"
-                                        "firstmatch=on,"
-                                        "loosescan=on,"
+                                        "firstmatch=off,"
+                                        "loosescan=off,"
                                         "materialization=off,"
                                         "in_to_exists=on,"
-                                        "semijoin=on,"
+                                        "semijoin=off,"
                                         "partial_match_rowid_merge=on,"
                                         "partial_match_table_scan=on,"
                                         "subquery_cache=on,"