MWL#89: Cost-based choice between Materialization and IN->EXISTS transformation

- Added more tests to the MWL#89 specific test, and made the test more modular.
- Updated test files.
- Fixed a memory leak.
- More comments.

mysql-test/r/subselect_mat.result:
  - Updated the test file to reflect the new optimizer switches related to
    materialized subquery execution.
  - Added one extra test to test all cases that expose BUG#40037 (this is an old bug from 5.x).
  - Updated the test result with correct results that expose BUG#40037.
mysql-test/t/subselect_mat.test:
  - Updated the test file to reflect the new optimizer switches related to
    materialized subquery execution.
  - Added one extra test to test all cases that expose BUG#40037 (this is an old bug from 5.x).
  - Updated the test result with correct results that expose BUG#40037.
sql/sql_select.cc:
  Fixed a memory leak reported by Valgrind.

7 files changed, 3940 insertions, 293 deletions

diff --git a/mysql-test/include/subselect_mat_cost.inc b/mysql-test/include/subselect_mat_cost.inc
new file mode 100644
index 00000000000..4ccbd08693a
--- /dev/null
+++ b/mysql-test/include/subselect_mat_cost.inc
@@ -0,0 +1,152 @@
+-- echo
+-- echo /* A. Subqueries in the SELECT clause. */
+explain
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+-- echo
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+-- echo
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+
+-- echo
+-- echo /*
+-- echo   B. "Natural" examples of subqueries without grouping that
+-- echo   cannot be flattened into semijoin.
+-- echo */
+
+explain
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+-- echo
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+-- echo UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+-- echo
+explain
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+-- echo
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+
+-- echo
+-- echo /* C. Subqueries in the WHERE clause with GROUP BY. */
+explain
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+-- echo
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+-- echo
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+-- echo
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+-- echo
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+-- echo
+explain
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+
+-- echo
+-- echo /*
+-- echo   D. Subqueries for which materialization is not possible, and the
+-- echo   optimizer reverts to in-to-exists.
+-- echo */
+# The first two cases are rejected during the prepare phase by the procedure
+# subquery_types_allow_materialization().
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+-- echo
+# The following two subqueries return the result of a string function with a
+# blob argument, where the return type may be != blob. These are rejected during
+# cost-based optimization when attempting to create a temporary table.
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+-- echo
+
+
+-- echo
+-- echo /* E. Edge cases. */
+-- echo
+
+-- echo /* E.1 Both materialization and in_to_exists cannot be off. */
+set @save_optimizer_switch=@@optimizer_switch;
+set @@optimizer_switch = 'materialization=off,in_to_exists=off';
+--error ER_ILLEGAL_SUBQUERY_OPTIMIZER_SWITCHES
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+set @@optimizer_switch = @save_optimizer_switch;
+
+-- echo /* E.2 Outer query without tables, always uses IN-TO-EXISTS. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+
+-- echo /* E.3 Subqueries without tables. */
+explain
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+-- echo UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+
+-- echo /* E.4 optimize_cond detects FALSE where/having clause. */
+explain
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+
+-- echo /* E.5 opt_sum_query detects no matching min/max row or substitutes MIN/MAX with a const. */
+-- echo TODO this test produces wrong result due to missing logic to handle the case
+-- echo when JOIN::optimize detects an empty subquery result.
+#explain
+#select a1 from t1 where a1 in (select max(b1) from t2);
+#select a1 from t1 where a1 in (select max(b1) from t2);
+-- echo
+#explain
+#select a1 from t1 where a1 in (select max(b1) from t2 where b1 = '7 - 02');
+#select a1 from t1 where a1 in (select max(b1) from t2 where b1 = '7 - 02');
+
+-- echo /* E.6 make_join_select detects impossible WHERE. *
+
+-- echo TODO
+
+-- echo /* E.7 constant optimization detects "no matching row in const table". */
+
+-- echo TODO
+
+-- echo /* E.8 Impossible WHERE noticed after reading const tables. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+
+-- echo
+-- echo /* F. UPDATE/DELETE with subqueries. */
+-- echo
+
+-- echo TODO
+-- echo
diff --git a/mysql-test/r/subselect_mat.result b/mysql-test/r/subselect_mat.result
index a4a69bb2f83..ca511caaabe 100644
--- a/mysql-test/r/subselect_mat.result
+++ b/mysql-test/r/subselect_mat.result
@@ -30,7 +30,7 @@ create index it3i3 on t3i (c1, c2);
 insert into t1i select * from t1;
 insert into t2i select * from t2;
 insert into t3i select * from t3;
-set @@optimizer_switch='semijoin=off';
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
 /******************************************************************************
 * Simple tests.
 ******************************************************************************/
@@ -176,33 +176,33 @@ a1	a2
 1 - 02	2 - 02
 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 @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=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,materialization=off';
+set @@optimizer_switch='materialization=off,in_to_exists=on,semijoin=on';
 execute st1;
 a1	a2
 1 - 01	2 - 01
 1 - 02	2 - 02
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=on';
 execute st1;
 a1	a2
 1 - 01	2 - 01
 1 - 02	2 - 02
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch='materialization=off,in_to_exists=on,semijoin=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='materialization=on,in_to_exists=off,semijoin=off';
 execute st1;
 a1	a2
 1 - 01	2 - 01
 1 - 02	2 - 02
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch='materialization=off,in_to_exists=on,semijoin=on';
 execute st1;
 a1	a2
 1 - 01	2 - 01
 1 - 02	2 - 02
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
 explain extended
 select * from t1 where (a1, a2) in (select b1, b2 from t2 order by b1, b2);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
@@ -549,7 +549,7 @@ a1	a2
 Test that BLOBs are not materialized (except when arguments of some functions).
 */
 # force materialization to be always considered
-set @@optimizer_switch='semijoin=off';
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
 set @prefix_len = 6;
 set @blob_len = 16;
 set @suffix_len = @blob_len - @prefix_len;
@@ -951,7 +951,7 @@ insert into t1bit values (b'010', b'110');
 insert into t2bit values (b'001', b'101');
 insert into t2bit values (b'010', b'110');
 insert into t2bit values (b'110', b'111');
-set @@optimizer_switch='semijoin=off';
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
 explain extended select bin(a1), bin(a2)
 from t1bit
 where (a1, a2) in (select b1, b2 from t2bit);
@@ -994,7 +994,7 @@ drop table t1, t2, t3, t1i, t2i, t3i, columns;
 /******************************************************************************
 * Test the cache of the left operand of IN.
 ******************************************************************************/
-set @@optimizer_switch='semijoin=off';
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
 create table t1 (s1 int);
 create table t2 (s2 int);
 insert into t1 values (5),(1),(0);
@@ -1136,27 +1136,40 @@ drop table t2;
 create table t1 (a1 int key);
 create table t2 (b1 int);
 insert into t1 values (5);
+Only the last query returns correct result. Filed as BUG#40037.
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
 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	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,materialization=off';
+NULL
+set @@optimizer_switch='materialization=off,in_to_exists=on,semijoin=off';
 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';
+NULL
+set @@optimizer_switch='materialization=on,in_to_exists=off,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	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';
+NULL
+set @@optimizer_switch='materialization=off,in_to_exists=on,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)
+NULL
+set @@optimizer_switch='materialization=off,in_to_exists=off,semijoin=on';
 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
@@ -1167,7 +1180,7 @@ drop table t1,t2;
 create table t1 (a char(2), b varchar(10));
 insert into t1 values ('a',  'aaa');
 insert into t1 values ('aa', 'aaaa');
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
 explain select a,b from t1 where b in (select a from t1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	Using where
@@ -1187,7 +1200,7 @@ INSERT INTO t1 (f1, f2) VALUES (10, 1.668);
 CREATE TABLE t2 LIKE t1;
 INSERT INTO t2 VALUES (1, 1.789);
 INSERT INTO t2 VALUES (13, 1.454);
-SET @@optimizer_switch='default,semijoin=on,materialization=on';
+SET @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=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	subselect2	ALL	unique_key	NULL	NULL	NULL	2	
@@ -1208,7 +1221,7 @@ PRIMARY KEY (pk)
 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 @@optimizer_switch='default,semijoin=on,materialization=on';
+SET @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=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	
@@ -1237,7 +1250,7 @@ i
 3
 4
 set @save_optimizer_switch=@@optimizer_switch;
-set session optimizer_switch='materialization=off';
+set session optimizer_switch='materialization=off,in_to_exists=on';
 select * from t1 where t1.i in (select t2.i from t2 join t3 where t2.i + t3.i = 5);
 i
 1
diff --git a/mysql-test/r/subselect_mat_cost.result b/mysql-test/r/subselect_mat_cost.result
index bfa4589bdd2..c6cb7685f4a 100644
--- a/mysql-test/r/subselect_mat_cost.result
+++ b/mysql-test/r/subselect_mat_cost.result
@@ -1,191 +1,3597 @@
-drop table if exists t1, t2, t3, t1i, t2i, t3i;
-create table t1 (a1 char(8), a2 char(8));
-create table t2 (b1 char(8), b2 char(8));
-create table t3 (c1 char(8), c2 char(8));
-Unindexed tables
-insert into t1 values ('1 - 00', '2 - 00');
-insert into t1 values ('1 - 01', '2 - 01');
-insert into t1 values ('1 - 02', '2 - 02');
-insert into t2 values ('1 - 01', '2 - 01');
-insert into t2 values ('1 - 01', '2 - 01');
-insert into t2 values ('1 - 02', '2 - 02');
-insert into t2 values ('1 - 02', '2 - 02');
-insert into t2 values ('1 - 03', '2 - 03');
-insert into t3 values ('1 - 01', '2 - 01');
-insert into t3 values ('1 - 02', '2 - 02');
-insert into t3 values ('1 - 03', '2 - 03');
-insert into t3 values ('1 - 04', '2 - 04');
-Indexed tables
-create table t1i (a1 char(8), a2 char(8));
-create table t2i (b1 char(8), b2 char(8));
-create table t3i (c1 char(8), c2 char(8));
-create index it1i1 on t1i (a1);
-create index it1i2 on t1i (a2);
-create index it1i3 on t1i (a1, a2);
-create index it2i1 on t2i (b1);
-create index it2i2 on t2i (b2);
-create index it2i3 on t2i (b1, b2);
-create index it3i1 on t3i (c1);
-create index it3i2 on t3i (c2);
-create index it3i3 on t3i (c1, c2);
-insert into t1i select * from t1;
-insert into t2i select * from t2;
-insert into t3i select * from t3;
-
-1. Both materialization and in-to-exists are possible to execute
+drop table if exists t1, t2, t1_1024, t2_1024;
+drop procedure if exists make_t1_indexes;
+drop procedure if exists make_t2_indexes;
+drop procedure if exists remove_t1_indexes;
+drop procedure if exists remove_t2_indexes;
+drop procedure if exists add_materialization_data;
+drop procedure if exists delete_materialization_data;
+drop procedure if exists set_all_columns_not_null;
+drop procedure if exists set_all_columns_nullable;
+create table t1 (a1 char(8), a2 char(8), a3 char(8), a4 int);
+insert into t1 values ('1 - 00', '2 - 00', '3 - 00', 0);
+insert into t1 values ('1 - 01', '2 - 01', '3 - 01', 1);
+insert into t1 values ('1 - 02', '2 - 02', '3 - 02', 2);
+create table t2 (b1 char(8), b2 char(8), b3 char(8), b4 int);
+insert into t2 values ('1 - 01', '2 - 01', '3 - 01', 1);
+insert into t2 values ('1 - 01', '2 - 01', '3 - 02', 2);
+insert into t2 values ('1 - 02', '2 - 02', '3 - 03', 3);
+insert into t2 values ('1 - 02', '2 - 02', '3 - 04', 4);
+insert into t2 values ('1 - 03', '2 - 03', '3 - 05', 5);
+create table t1_1024 (a1 blob(1024), a2 blob(1024));
+insert into t1_1024 values (concat('1 - 00', repeat('x', 1018)), concat('2 - 00', repeat('x', 1018)));
+insert into t1_1024 values (concat('1 - 01', repeat('x', 1018)), concat('2 - 01', repeat('x', 1018)));
+create table t2_1024 (b1 blob(1024), b2 blob(1024));
+insert into t2_1024 values (concat('1 - 01', repeat('x', 1018)), concat('2 - 01', repeat('x', 1018)));
+insert into t2_1024 values (concat('1 - 02', repeat('x', 1018)), concat('2 - 02', repeat('x', 1018)));
+insert into t2_1024 values (concat('1 - 03', repeat('x', 1018)), concat('2 - 03', repeat('x', 1018)));
+insert into t2_1024 values (concat('1 - 04', repeat('x', 1018)), concat('2 - 04', repeat('x', 1018)));
+create procedure make_t1_indexes()
+begin
+create index it1i1 on t1 (a1);
+create index it1i2 on t1 (a2);
+create index it1i3 on t1 (a1, a2);
+create index it1_1024i1 on t1_1024 (a1(6));
+create index it1_1024i2 on t1_1024 (a2(6));
+create index it1_1024i3 on t1_1024 (a1(6), a2(6));
+end|
+create procedure make_t2_indexes()
+begin
+create index it2i1 on t2 (b1);
+create index it2i2 on t2 (b2);
+create index it2i3 on t2 (b1, b2);
+create unique index it2i4 on t2 (b1, b2, b3);
+create index it2_1024i1 on t2_1024 (b1(6));
+create index it2_1024i2 on t2_1024 (b2(6));
+create index it2_1024i3 on t2_1024 (b1(6), b2(6));
+end|
+create procedure remove_t1_indexes()
+begin
+drop index it1i1 on t1;
+drop index it1i2 on t1;
+drop index it1i3 on t1;
+drop index it1_1024i1 on t1_1024;
+drop index it1_1024i2 on t1_1024;
+drop index it1_1024i3 on t1_1024;
+end|
+create procedure remove_t2_indexes()
+begin
+drop index it2i1 on t2;
+drop index it2i2 on t2;
+drop index it2i3 on t2;
+drop index it2i4 on t2;
+drop index it2_1024i1 on t2_1024;
+drop index it2_1024i2 on t2_1024;
+drop index it2_1024i3 on t2_1024;
+end|
+create procedure add_materialization_data()
+begin
+insert into t1 values ('1 - 03', '2 - 03', '3 - 03', 3);
+insert into t1 values ('1 - 04', '2 - 04', '3 - 04', 4);
+insert into t1 values ('1 - 05', '2 - 05', '3 - 05', 5);
+insert into t1 values ('1 - 06', '2 - 06', '3 - 06', 6);
+insert into t1 values ('1 - 07', '2 - 07', '3 - 07', 7);
+insert into t1_1024 values (concat('1 - 03', repeat('x', 1018)), concat('2 - 03', repeat('x', 1018)));
+end|
+create procedure delete_materialization_data()
+begin
+delete from t1 where a1 >= '1 - 03';
+delete from t1_1024 where a1 >= '1 - 03';
+end|
+create procedure set_all_columns_not_null()
+begin
+alter table t1 modify a1 char(8) not null, modify a2 char(8) not null, modify a3 char(8) not null;
+alter table t2 modify b1 char(8) not null, modify b2 char(8) not null, modify b3 char(8) not null;
+end|
+create procedure set_all_columns_nullable()
+begin
+alter table t1 modify a1 char(8) null, modify a2 char(8) null, modify a3 char(8) null;
+alter table t2 modify b1 char(8) null, modify b2 char(8) null, modify b3 char(8) null;
+end|
 
+/******************************************************************************
+1. Both materialization and in-to-exists are ON, make a cost-based choice.
+******************************************************************************/
 set @@optimizer_switch='materialization=on,in_to_exists=on';
 
-1.1 In-to-exists is cheaper
-set @@optimizer_switch='semijoin=off';
-explain extended
-select * from t1 where a1 in (select b1 from t2 where b1 > '0');
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
-2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where
-Warnings:
-Note	1003	select `test`.`t1`.`a1` AS `a1`,`test`.`t1`.`a2` AS `a2` from `test`.`t1` where <in_optimizer>(`test`.`t1`.`a1`,<exists>(select `test`.`t2`.`b1` from `test`.`t2` where ((`test`.`t2`.`b1` > '0') and (<cache>(`test`.`t1`.`a1`) = `test`.`t2`.`b1`))))
-select * from t1 where a1 in (select b1 from t2 where b1 > '0');
+/* 1.1 In-to-exists is cheaper */
+call make_t1_indexes();
+/* 1.1.1 non-indexed table access */
+
+/* A. Subqueries in the SELECT clause. */
+explain
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i1	9	NULL	3	Using index
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+a1	a1 in (select b1 from t2 where b1 > '0')
+1 - 00	0
+1 - 01	1
+1 - 02	1
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	18	NULL	3	Using index
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	18	NULL	3	Using index
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+
+/*
+B. "Natural" examples of subqueries without grouping that
+cannot be flattened into semijoin.
+*/
+explain
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	18	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	18	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
 a1	a2
+1 - 00	2 - 00
 1 - 01	2 - 01
 1 - 02	2 - 02
-explain extended
-select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0');
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
-2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where
-Warnings:
-Note	1003	select `test`.`t1`.`a1` AS `a1`,`test`.`t1`.`a2` AS `a2` from `test`.`t1` where <in_optimizer>((`test`.`t1`.`a1`,`test`.`t1`.`a2`),<exists>(select `test`.`t2`.`b1`,`test`.`t2`.`b2` from `test`.`t2` where ((`test`.`t2`.`b1` > '0') and (<cache>(`test`.`t1`.`a1`) = `test`.`t2`.`b1`) and (<cache>(`test`.`t1`.`a2`) = `test`.`t2`.`b2`))))
-select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0');
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i2	9	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+3	DEPENDENT UNION	t3	ALL	NULL	NULL	NULL	NULL	5	Using where
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+a2
+2 - 01
+2 - 02
+
+explain
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ref	it1i1,it1i3	it1i1	9	const	1	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+a1
+1 - 02
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	18	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
 a1	a2
 1 - 01	2 - 01
 1 - 02	2 - 02
-set @@optimizer_switch='semijoin=on';
-explain extended
+
+/* C. Subqueries in the WHERE clause with GROUP BY. */
+explain
 select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
-2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where; Using temporary; Using filesort
-Warnings:
-Note	1003	select `test`.`t1`.`a1` AS `a1`,`test`.`t1`.`a2` AS `a2` from `test`.`t1` where <in_optimizer>(`test`.`t1`.`a1`,<exists>(select `test`.`t2`.`b1` from `test`.`t2` where (`test`.`t2`.`b1` > '0') group by `test`.`t2`.`b1` having (<cache>(`test`.`t1`.`a1`) = <ref_null_helper>(`test`.`t2`.`b1`))))
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using temporary; Using filesort
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+a1	a2	a3	a4
+
+explain
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+/*
+D. Subqueries for which materialization is not possible, and the
+optimizer reverts to in-to-exists.
+*/
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	ALL	NULL	NULL	NULL	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	ALL	NULL	NULL	NULL	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	ALL	NULL	NULL	NULL	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	ALL	NULL	NULL	NULL	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+
+
+/* E. Edge cases. */
+
+/* E.1 Both materialization and in_to_exists cannot be off. */
+set @save_optimizer_switch=@@optimizer_switch;
+set @@optimizer_switch = 'materialization=off,in_to_exists=off';
 select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+ERROR HY000: At least one of the 'in_to_exists' or 'materialization' optimizer_switch flags must be 'on'.
+set @@optimizer_switch = @save_optimizer_switch;
+/* E.2 Outer query without tables, always uses IN-TO-EXISTS. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+'1 - 03' in (select b1 from t2 where b1 > '0')
+1
+/* E.3 Subqueries without tables. */
+explain
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i1,it1i2,it1i3	it1i3	18	NULL	3	Using where; Using index
+Warnings:
+Note	1249	Select 2 was reduced during optimization
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i1	9	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	DEPENDENT UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+a1
+1 - 02
+/* E.4 optimize_cond detects FALSE where/having clause. */
+explain
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	18	NULL	3	Using where; Using index
+2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+/* E.5 opt_sum_query detects no matching min/max row or substitutes MIN/MAX with a const. */
+TODO this test produces wrong result due to missing logic to handle the case
+when JOIN::optimize detects an empty subquery result.
+
+/* E.6 make_join_select detects impossible WHERE. *
+TODO
+/* E.7 constant optimization detects "no matching row in const table". */
+TODO
+/* E.8 Impossible WHERE noticed after reading const tables. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+'1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0')
+0
+
+/* F. UPDATE/DELETE with subqueries. */
+
+TODO
+
+/* 1.1.2 indexed table access, nullabale columns. */
+call make_t2_indexes();
+
+/* A. Subqueries in the SELECT clause. */
+explain
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i1	9	NULL	3	Using index
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i3	it2i1	9	func	2	Using index; Using where; Full scan on NULL key
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+a1	a1 in (select b1 from t2 where b1 > '0')
+1 - 00	0
+1 - 01	1
+1 - 02	1
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	18	NULL	3	Using index
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i2,it2i3	it2i3	9	func	2	Using index; Using where; Full scan on NULL key
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	18	NULL	3	Using index
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i2,it2i3	it2i3	9	func	2	Using index; Using where; Full scan on NULL key
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+
+/*
+B. "Natural" examples of subqueries without grouping that
+cannot be flattened into semijoin.
+*/
+explain
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	18	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i2	it2i2	9	func	2	Using index
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	18	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i2,it2i3	it2i4	18	func,func	1	Using index; Using where
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+a1	a2
+1 - 00	2 - 00
+1 - 01	2 - 01
+1 - 02	2 - 02
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i2	9	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	ref	it2i2	it2i2	9	func	2	Using index
+3	DEPENDENT UNION	t3	index	NULL	it2i4	27	NULL	5	Using where; Using index
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+a2
+2 - 01
+2 - 02
+
+explain
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ref	it1i1,it1i3	it1i1	9	const	1	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	ref	it2i2	it2i2	9	const	1	Using index condition
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+a1
+1 - 02
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	18	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i2,it2i3	it2i4	18	func,func	1	Using index; Using where
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
 a1	a2
 1 - 01	2 - 01
 1 - 02	2 - 02
-explain extended
+
+/* C. Subqueries in the WHERE clause with GROUP BY. */
+explain
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i1	9	NULL	1	Using where; Using index
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
 select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
-2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where; Using temporary; Using filesort
-Warnings:
-Note	1003	select `test`.`t1`.`a1` AS `a1`,`test`.`t1`.`a2` AS `a2` from `test`.`t1` where <in_optimizer>((`test`.`t1`.`a1`,`test`.`t1`.`a2`),<exists>(select `test`.`t2`.`b1`,`test`.`t2`.`b2` from `test`.`t2` where (`test`.`t2`.`b1` > '0') group by `test`.`t2`.`b1`,`test`.`t2`.`b2` having (((<cache>(`test`.`t1`.`a1`) = `test`.`t2`.`b1`) or isnull(`test`.`t2`.`b1`)) and ((<cache>(`test`.`t1`.`a2`) = `test`.`t2`.`b2`) or isnull(`test`.`t2`.`b2`)) and <is_not_null_test>(`test`.`t2`.`b1`) and <is_not_null_test>(`test`.`t2`.`b2`))))
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i3	18	NULL	1	Using where; Using index
 select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i3	18	NULL	1	Using where; Using index
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	index	NULL	it2i4	27	NULL	1	Using index
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	index	NULL	it2i4	27	NULL	1	Using where; Using index
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+a1	a2	a3	a4
+
+explain
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	range	it2i4,it2i1,it2i3	it2i4	27	NULL	2	Using where; Using index for group-by
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+/*
+D. Subqueries for which materialization is not possible, and the
+optimizer reverts to in-to-exists.
+*/
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	index_subquery	it2_1024i1,it2_1024i3	it2_1024i3	9	func	1	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	index_subquery	it2_1024i1,it2_1024i2,it2_1024i3	it2_1024i1	9	func	2	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	range	it2_1024i1,it2_1024i3	it2_1024i1	9	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	range	it2_1024i1,it2_1024i3	it2_1024i1	9	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+
+
+/* E. Edge cases. */
+
+/* E.1 Both materialization and in_to_exists cannot be off. */
+set @save_optimizer_switch=@@optimizer_switch;
+set @@optimizer_switch = 'materialization=off,in_to_exists=off';
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+ERROR HY000: At least one of the 'in_to_exists' or 'materialization' optimizer_switch flags must be 'on'.
+set @@optimizer_switch = @save_optimizer_switch;
+/* E.2 Outer query without tables, always uses IN-TO-EXISTS. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i3	it2i1	9	const	2	Using index; Using where
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+'1 - 03' in (select b1 from t2 where b1 > '0')
+1
+/* E.3 Subqueries without tables. */
+explain
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i1,it1i2,it1i3	it1i3	18	NULL	3	Using where; Using index
+Warnings:
+Note	1249	Select 2 was reduced during optimization
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i1	9	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	DEPENDENT UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+a1
+1 - 02
+/* E.4 optimize_cond detects FALSE where/having clause. */
+explain
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	18	NULL	3	Using where; Using index
+2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+/* E.5 opt_sum_query detects no matching min/max row or substitutes MIN/MAX with a const. */
+TODO this test produces wrong result due to missing logic to handle the case
+when JOIN::optimize detects an empty subquery result.
+
+/* E.6 make_join_select detects impossible WHERE. *
+TODO
+/* E.7 constant optimization detects "no matching row in const table". */
+TODO
+/* E.8 Impossible WHERE noticed after reading const tables. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+'1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0')
+0
+
+/* F. UPDATE/DELETE with subqueries. */
+
+TODO
+
+/* 1.1.3 indexed table access, non-nullabale columns. */
+call set_all_columns_not_null();
+
+/* A. Subqueries in the SELECT clause. */
+explain
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i1	8	NULL	3	Using index
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i3	it2i4	8	func	1	Using index; Using where
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+a1	a1 in (select b1 from t2 where b1 > '0')
+1 - 00	0
+1 - 01	1
+1 - 02	1
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	16	NULL	3	Using index
+2	DEPENDENT SUBQUERY	t2	ref	it2i4,it2i1,it2i2,it2i3	it2i4	8	func	2	Using where; Using index
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	16	NULL	3	Using index
+2	DEPENDENT SUBQUERY	t2	ref	it2i4,it2i1,it2i2,it2i3	it2i4	8	func	2	Using where; Using index
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+
+/*
+B. "Natural" examples of subqueries without grouping that
+cannot be flattened into semijoin.
+*/
+explain
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	16	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i2	it2i2	8	func	2	Using index
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	16	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i2,it2i3	it2i4	16	func,func	1	Using index; Using where
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
 a1	a2
+1 - 00	2 - 00
 1 - 01	2 - 01
 1 - 02	2 - 02
-explain extended
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i2	8	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	ref	it2i2	it2i2	8	func	2	Using index
+3	DEPENDENT UNION	t3	index	NULL	it2i4	24	NULL	5	Using where; Using index
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+a2
+2 - 01
+2 - 02
+
+explain
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ref	it1i1,it1i3	it1i1	8	const	1	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	ref	it2i2	it2i2	8	const	1	Using index condition
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+a1
+1 - 02
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	16	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i2,it2i3	it2i4	16	func,func	1	Using index; Using where
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+a1	a2
+1 - 01	2 - 01
+1 - 02	2 - 02
+
+/* C. Subqueries in the WHERE clause with GROUP BY. */
+explain
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i1	8	NULL	1	Using where; Using index
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i3	16	NULL	1	Using where; Using index
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
 select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
-2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where; Using temporary; Using filesort
-Warnings:
-Note	1003	select `test`.`t1`.`a1` AS `a1`,`test`.`t1`.`a2` AS `a2` from `test`.`t1` where <in_optimizer>((`test`.`t1`.`a1`,`test`.`t1`.`a2`),<exists>(select `test`.`t2`.`b1`,`test`.`t2`.`b2` from `test`.`t2` where (`test`.`t2`.`b1` > '0') group by `test`.`t2`.`b1`,`test`.`t2`.`b2` having ((`test`.`t2`.`b2` < '2 - 04') and ((<cache>(`test`.`t1`.`a1`) = `test`.`t2`.`b1`) or isnull(`test`.`t2`.`b1`)) and ((<cache>(`test`.`t1`.`a2`) = `test`.`t2`.`b2`) or isnull(`test`.`t2`.`b2`)) and <is_not_null_test>(`test`.`t2`.`b1`) and <is_not_null_test>(`test`.`t2`.`b2`))))
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i3	16	NULL	1	Using where; Using index
 select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	index	NULL	it2i4	24	NULL	1	Using index
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	index	NULL	it2i4	24	NULL	1	Using where; Using index
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+a1	a2	a3	a4
+
+explain
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2	range	it2i4,it2i1,it2i3	it2i4	24	NULL	2	Using where; Using index for group-by
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+/*
+D. Subqueries for which materialization is not possible, and the
+optimizer reverts to in-to-exists.
+*/
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	index_subquery	it2_1024i1,it2_1024i3	it2_1024i3	9	func	1	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	index_subquery	it2_1024i1,it2_1024i2,it2_1024i3	it2_1024i1	9	func	2	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	range	it2_1024i1,it2_1024i3	it2_1024i1	9	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	range	it2_1024i1,it2_1024i3	it2_1024i1	9	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+
+
+/* E. Edge cases. */
+
+/* E.1 Both materialization and in_to_exists cannot be off. */
+set @save_optimizer_switch=@@optimizer_switch;
+set @@optimizer_switch = 'materialization=off,in_to_exists=off';
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+ERROR HY000: At least one of the 'in_to_exists' or 'materialization' optimizer_switch flags must be 'on'.
+set @@optimizer_switch = @save_optimizer_switch;
+/* E.2 Outer query without tables, always uses IN-TO-EXISTS. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i3	it2i1	8	const	5	Using index; Using where
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+'1 - 03' in (select b1 from t2 where b1 > '0')
+1
+/* E.3 Subqueries without tables. */
+explain
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i1,it1i2,it1i3	it1i3	16	NULL	3	Using where; Using index
+Warnings:
+Note	1249	Select 2 was reduced during optimization
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i1	8	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	DEPENDENT UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+a1
+1 - 02
+/* E.4 optimize_cond detects FALSE where/having clause. */
+explain
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	16	NULL	3	Using where; Using index
+2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+/* E.5 opt_sum_query detects no matching min/max row or substitutes MIN/MAX with a const. */
+TODO this test produces wrong result due to missing logic to handle the case
+when JOIN::optimize detects an empty subquery result.
+
+/* E.6 make_join_select detects impossible WHERE. *
+TODO
+/* E.7 constant optimization detects "no matching row in const table". */
+TODO
+/* E.8 Impossible WHERE noticed after reading const tables. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+'1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0')
+0
+
+/* F. UPDATE/DELETE with subqueries. */
+
+TODO
+
+call set_all_columns_nullable();
+
+/* 1.2 Materialization is cheaper */
+call add_materialization_data();
+call remove_t1_indexes();
+/* 1.2.1 non-indexed table access */
+call remove_t2_indexes();
+
+/* A. Subqueries in the SELECT clause. */
+explain
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+a1	a1 in (select b1 from t2 where b1 > '0')
+1 - 00	0
+1 - 01	1
+1 - 02	1
+1 - 03	1
+1 - 04	0
+1 - 05	0
+1 - 06	0
+1 - 07	0
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+1 - 03	2 - 03	1
+1 - 04	2 - 04	0
+1 - 05	2 - 05	0
+1 - 06	2 - 06	0
+1 - 07	2 - 07	0
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+1 - 03	2 - 03	1
+1 - 04	2 - 04	0
+1 - 05	2 - 05	0
+1 - 06	2 - 06	0
+1 - 07	2 - 07	0
+
+/*
+B. "Natural" examples of subqueries without grouping that
+cannot be flattened into semijoin.
+*/
+explain
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+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	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+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	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
 a1	a2
+1 - 00	2 - 00
 1 - 01	2 - 01
 1 - 02	2 - 02
+1 - 03	2 - 03
+1 - 04	2 - 04
+1 - 05	2 - 05
+1 - 06	2 - 06
+1 - 07	2 - 07
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+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	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+3	DEPENDENT UNION	t3	ALL	NULL	NULL	NULL	NULL	5	Using where
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+a2
+2 - 01
+2 - 02
+2 - 03
 
-1.2 Materialization is cheaper
-1.2.1 Materialization is executable
-insert into t1 values ('1 - 03', '2 - 03');
-insert into t1 values ('1 - 04', '2 - 04');
-insert into t1 values ('1 - 05', '2 - 05');
-set @@optimizer_switch='semijoin=off';
-explain extended
-select * from t1 where a1 in (select b1 from t2 where b1 > '0');
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	6	100.00	Using where
-2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where
-Warnings:
-Note	1003	select `test`.`t1`.`a1` AS `a1`,`test`.`t1`.`a2` AS `a2` from `test`.`t1` where <in_optimizer>(`test`.`t1`.`a1`,`test`.`t1`.`a1` in ( <materialize> (select `test`.`t2`.`b1` from `test`.`t2` where (`test`.`t2`.`b1` > '0') ), <primary_index_lookup>(`test`.`t1`.`a1` in <temporary table> on distinct_key where ((`test`.`t1`.`a1` = `materialized subselect`.`b1`)))))
-select * from t1 where a1 in (select b1 from t2 where b1 > '0');
+explain
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+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	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+a1
+1 - 02
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+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	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
 a1	a2
 1 - 01	2 - 01
 1 - 02	2 - 02
 1 - 03	2 - 03
-explain extended
-select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0');
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	6	100.00	Using where
-2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where
+
+/* C. Subqueries in the WHERE clause with GROUP BY. */
+explain
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+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	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+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	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+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	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+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	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using temporary; Using filesort
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+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	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+a1	a2	a3	a4
+
+explain
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+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	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+/*
+D. Subqueries for which materialization is not possible, and the
+optimizer reverts to in-to-exists.
+*/
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	ALL	NULL	NULL	NULL	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	ALL	NULL	NULL	NULL	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	ALL	NULL	NULL	NULL	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	ALL	NULL	NULL	NULL	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+
+
+/* E. Edge cases. */
+
+/* E.1 Both materialization and in_to_exists cannot be off. */
+set @save_optimizer_switch=@@optimizer_switch;
+set @@optimizer_switch = 'materialization=off,in_to_exists=off';
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+ERROR HY000: At least one of the 'in_to_exists' or 'materialization' optimizer_switch flags must be 'on'.
+set @@optimizer_switch = @save_optimizer_switch;
+/* E.2 Outer query without tables, always uses IN-TO-EXISTS. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+'1 - 03' in (select b1 from t2 where b1 > '0')
+1
+/* E.3 Subqueries without tables. */
+explain
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	Using where
 Warnings:
-Note	1003	select `test`.`t1`.`a1` AS `a1`,`test`.`t1`.`a2` AS `a2` from `test`.`t1` where <in_optimizer>((`test`.`t1`.`a1`,`test`.`t1`.`a2`),(`test`.`t1`.`a1`,`test`.`t1`.`a2`) in ( <materialize> (select `test`.`t2`.`b1`,`test`.`t2`.`b2` from `test`.`t2` where (`test`.`t2`.`b1` > '0') ), <primary_index_lookup>(`test`.`t1`.`a1` in <temporary table> on distinct_key where ((`test`.`t1`.`a1` = `materialized subselect`.`b1`) and (`test`.`t1`.`a2` = `materialized subselect`.`b2`)))))
-select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0');
+Note	1249	Select 2 was reduced during optimization
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+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	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	DEPENDENT UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+a1
+1 - 02
+1 - 03
+/* E.4 optimize_cond detects FALSE where/having clause. */
+explain
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+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	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+/* E.5 opt_sum_query detects no matching min/max row or substitutes MIN/MAX with a const. */
+TODO this test produces wrong result due to missing logic to handle the case
+when JOIN::optimize detects an empty subquery result.
+
+/* E.6 make_join_select detects impossible WHERE. *
+TODO
+/* E.7 constant optimization detects "no matching row in const table". */
+TODO
+/* E.8 Impossible WHERE noticed after reading const tables. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+'1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0')
+0
+
+/* F. UPDATE/DELETE with subqueries. */
+
+TODO
+
+/* 1.2.2 indexed table access, nullabale columns. */
+call make_t2_indexes();
+
+/* A. Subqueries in the SELECT clause. */
+explain
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i1	9	NULL	5	Using where; Using index
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+a1	a1 in (select b1 from t2 where b1 > '0')
+1 - 00	0
+1 - 01	1
+1 - 02	1
+1 - 03	1
+1 - 04	0
+1 - 05	0
+1 - 06	0
+1 - 07	0
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	SUBQUERY	t2	index	it2i4,it2i1,it2i2,it2i3	it2i3	18	NULL	5	Using where; Using index
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+1 - 03	2 - 03	1
+1 - 04	2 - 04	0
+1 - 05	2 - 05	0
+1 - 06	2 - 06	0
+1 - 07	2 - 07	0
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	SUBQUERY	t2	range	it2i4,it2i1,it2i2,it2i3	it2i3	9	NULL	4	Using where; Using index
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+1 - 03	2 - 03	1
+1 - 04	2 - 04	0
+1 - 05	2 - 05	0
+1 - 06	2 - 06	0
+1 - 07	2 - 07	0
+
+/*
+B. "Natural" examples of subqueries without grouping that
+cannot be flattened into semijoin.
+*/
+explain
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+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	SUBQUERY	t2	index	it2i2	it2i2	9	NULL	5	Using index
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+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	SUBQUERY	t2	index	it2i4,it2i1,it2i2,it2i3	it2i3	18	NULL	5	Using where; Using index
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+a1	a2
+1 - 00	2 - 00
+1 - 01	2 - 01
+1 - 02	2 - 02
+1 - 03	2 - 03
+1 - 04	2 - 04
+1 - 05	2 - 05
+1 - 06	2 - 06
+1 - 07	2 - 07
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+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	t2	ref	it2i2	it2i2	9	func	2	Using index
+3	DEPENDENT UNION	t3	index	NULL	it2i4	27	NULL	5	Using where; Using index
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+a2
+2 - 01
+2 - 02
+2 - 03
+
+explain
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+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	SUBQUERY	t2	ref	it2i2	it2i2	9	const	1	Using index condition
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+a1
+1 - 02
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+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	SUBQUERY	t2	index	it2i4,it2i1,it2i2,it2i3	it2i4	27	NULL	5	Using index
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
 a1	a2
 1 - 01	2 - 01
 1 - 02	2 - 02
 1 - 03	2 - 03
-set @@optimizer_switch='semijoin=on';
-explain extended
+
+/* C. Subqueries in the WHERE clause with GROUP BY. */
+explain
 select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	6	100.00	Using where
-2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where; Using temporary; Using filesort
-Warnings:
-Note	1003	select `test`.`t1`.`a1` AS `a1`,`test`.`t1`.`a2` AS `a2` from `test`.`t1` where <in_optimizer>(`test`.`t1`.`a1`,`test`.`t1`.`a1` in ( <materialize> (select `test`.`t2`.`b1` from `test`.`t2` where (`test`.`t2`.`b1` > '0') group by `test`.`t2`.`b1` ), <primary_index_lookup>(`test`.`t1`.`a1` in <temporary table> on distinct_key where ((`test`.`t1`.`a1` = `materialized subselect`.`b1`)))))
+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	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i1	9	NULL	5	Using where; Using index
 select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+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	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i3	18	NULL	5	Using where; Using index
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+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	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i3	18	NULL	5	Using where; Using index
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+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	SUBQUERY	t2	range	NULL	it2i4	27	NULL	6	Using index for group-by
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+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	SUBQUERY	t2	range	NULL	it2i4	27	NULL	6	Using where; Using index for group-by
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+a1	a2	a3	a4
+
+explain
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+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	SUBQUERY	t2	range	it2i4,it2i1,it2i3	it2i4	27	NULL	2	Using where; Using index for group-by
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+/*
+D. Subqueries for which materialization is not possible, and the
+optimizer reverts to in-to-exists.
+*/
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	index_subquery	it2_1024i1,it2_1024i3	it2_1024i3	9	func	1	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	index_subquery	it2_1024i1,it2_1024i2,it2_1024i3	it2_1024i1	9	func	2	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	range	it2_1024i1,it2_1024i3	it2_1024i1	9	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	range	it2_1024i1,it2_1024i3	it2_1024i1	9	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+
+
+/* E. Edge cases. */
+
+/* E.1 Both materialization and in_to_exists cannot be off. */
+set @save_optimizer_switch=@@optimizer_switch;
+set @@optimizer_switch = 'materialization=off,in_to_exists=off';
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+ERROR HY000: At least one of the 'in_to_exists' or 'materialization' optimizer_switch flags must be 'on'.
+set @@optimizer_switch = @save_optimizer_switch;
+/* E.2 Outer query without tables, always uses IN-TO-EXISTS. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i3	it2i1	9	const	2	Using index; Using where
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+'1 - 03' in (select b1 from t2 where b1 > '0')
+1
+/* E.3 Subqueries without tables. */
+explain
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	Using where
+Warnings:
+Note	1249	Select 2 was reduced during optimization
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+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	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	DEPENDENT UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+a1
+1 - 02
+1 - 03
+/* E.4 optimize_cond detects FALSE where/having clause. */
+explain
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+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	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+/* E.5 opt_sum_query detects no matching min/max row or substitutes MIN/MAX with a const. */
+TODO this test produces wrong result due to missing logic to handle the case
+when JOIN::optimize detects an empty subquery result.
+
+/* E.6 make_join_select detects impossible WHERE. *
+TODO
+/* E.7 constant optimization detects "no matching row in const table". */
+TODO
+/* E.8 Impossible WHERE noticed after reading const tables. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+'1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0')
+0
+
+/* F. UPDATE/DELETE with subqueries. */
+
+TODO
+
+/* 1.2.3 indexed table access, non-nullabale columns. */
+call set_all_columns_not_null();
+
+/* A. Subqueries in the SELECT clause. */
+explain
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i1	8	NULL	5	Using where; Using index
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+a1	a1 in (select b1 from t2 where b1 > '0')
+1 - 00	0
+1 - 01	1
+1 - 02	1
+1 - 03	1
+1 - 04	0
+1 - 05	0
+1 - 06	0
+1 - 07	0
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	SUBQUERY	t2	index	it2i4,it2i1,it2i2,it2i3	it2i3	16	NULL	5	Using where; Using index
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+1 - 03	2 - 03	1
+1 - 04	2 - 04	0
+1 - 05	2 - 05	0
+1 - 06	2 - 06	0
+1 - 07	2 - 07	0
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	SUBQUERY	t2	range	it2i4,it2i1,it2i2,it2i3	it2i3	8	NULL	4	Using where; Using index
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+1 - 03	2 - 03	1
+1 - 04	2 - 04	0
+1 - 05	2 - 05	0
+1 - 06	2 - 06	0
+1 - 07	2 - 07	0
+
+/*
+B. "Natural" examples of subqueries without grouping that
+cannot be flattened into semijoin.
+*/
+explain
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+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	SUBQUERY	t2	index	it2i2	it2i2	8	NULL	5	Using index
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+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	SUBQUERY	t2	index	it2i4,it2i1,it2i2,it2i3	it2i3	16	NULL	5	Using where; Using index
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
 a1	a2
+1 - 00	2 - 00
 1 - 01	2 - 01
 1 - 02	2 - 02
 1 - 03	2 - 03
-explain extended
+1 - 04	2 - 04
+1 - 05	2 - 05
+1 - 06	2 - 06
+1 - 07	2 - 07
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+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	t2	ref	it2i2	it2i2	8	func	2	Using index
+3	DEPENDENT UNION	t3	index	NULL	it2i4	24	NULL	5	Using where; Using index
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+a2
+2 - 01
+2 - 02
+2 - 03
+
+explain
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+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	SUBQUERY	t2	ref	it2i2	it2i2	8	const	1	Using index condition
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+a1
+1 - 02
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+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	SUBQUERY	t2	index	it2i4,it2i1,it2i2,it2i3	it2i4	24	NULL	5	Using index
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+a1	a2
+1 - 01	2 - 01
+1 - 02	2 - 02
+1 - 03	2 - 03
+
+/* C. Subqueries in the WHERE clause with GROUP BY. */
+explain
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+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	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i1	8	NULL	5	Using where; Using index
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
+
+explain
 select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	6	100.00	Using where
-2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where; Using temporary; Using filesort
-Warnings:
-Note	1003	select `test`.`t1`.`a1` AS `a1`,`test`.`t1`.`a2` AS `a2` from `test`.`t1` where <in_optimizer>((`test`.`t1`.`a1`,`test`.`t1`.`a2`),(`test`.`t1`.`a1`,`test`.`t1`.`a2`) in ( <materialize> (select `test`.`t2`.`b1`,`test`.`t2`.`b2` from `test`.`t2` where (`test`.`t2`.`b1` > '0') group by `test`.`t2`.`b1`,`test`.`t2`.`b2` ), <primary_index_lookup>(`test`.`t1`.`a1` in <temporary table> on distinct_key where ((`test`.`t1`.`a1` = `materialized subselect`.`b1`) and (`test`.`t1`.`a2` = `materialized subselect`.`b2`)))))
+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	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i3	16	NULL	5	Using where; Using index
 select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+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	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i3	16	NULL	5	Using where; Using index
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+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	SUBQUERY	t2	range	NULL	it2i4	24	NULL	6	Using index for group-by
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+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	SUBQUERY	t2	range	NULL	it2i4	24	NULL	6	Using where; Using index for group-by
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+a1	a2	a3	a4
+
+explain
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+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	SUBQUERY	t2	range	it2i4,it2i1,it2i3	it2i4	24	NULL	2	Using where; Using index for group-by
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+/*
+D. Subqueries for which materialization is not possible, and the
+optimizer reverts to in-to-exists.
+*/
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	index_subquery	it2_1024i1,it2_1024i3	it2_1024i3	9	func	1	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	index_subquery	it2_1024i1,it2_1024i2,it2_1024i3	it2_1024i1	9	func	2	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	range	it2_1024i1,it2_1024i3	it2_1024i1	9	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	range	it2_1024i1,it2_1024i3	it2_1024i1	9	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+
+
+/* E. Edge cases. */
+
+/* E.1 Both materialization and in_to_exists cannot be off. */
+set @save_optimizer_switch=@@optimizer_switch;
+set @@optimizer_switch = 'materialization=off,in_to_exists=off';
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+ERROR HY000: At least one of the 'in_to_exists' or 'materialization' optimizer_switch flags must be 'on'.
+set @@optimizer_switch = @save_optimizer_switch;
+/* E.2 Outer query without tables, always uses IN-TO-EXISTS. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i3	it2i1	8	const	5	Using index; Using where
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+'1 - 03' in (select b1 from t2 where b1 > '0')
+1
+/* E.3 Subqueries without tables. */
+explain
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	Using where
+Warnings:
+Note	1249	Select 2 was reduced during optimization
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+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	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	DEPENDENT UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+a1
+1 - 02
+1 - 03
+/* E.4 optimize_cond detects FALSE where/having clause. */
+explain
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+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	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+/* E.5 opt_sum_query detects no matching min/max row or substitutes MIN/MAX with a const. */
+TODO this test produces wrong result due to missing logic to handle the case
+when JOIN::optimize detects an empty subquery result.
+
+/* E.6 make_join_select detects impossible WHERE. *
+TODO
+/* E.7 constant optimization detects "no matching row in const table". */
+TODO
+/* E.8 Impossible WHERE noticed after reading const tables. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+'1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0')
+0
+
+/* F. UPDATE/DELETE with subqueries. */
+
+TODO
+
+call set_all_columns_nullable();
+/******************************************************************************
+2. Materialization is OFF, in-to-exists is ON, materialization is cheaper.
+******************************************************************************/
+set @@optimizer_switch='materialization=off,in_to_exists=on';
+/* 2.1 non-indexed table access */
+call remove_t2_indexes();
+
+/* A. Subqueries in the SELECT clause. */
+explain
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+a1	a1 in (select b1 from t2 where b1 > '0')
+1 - 00	0
+1 - 01	1
+1 - 02	1
+1 - 03	1
+1 - 04	0
+1 - 05	0
+1 - 06	0
+1 - 07	0
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+1 - 03	2 - 03	1
+1 - 04	2 - 04	0
+1 - 05	2 - 05	0
+1 - 06	2 - 06	0
+1 - 07	2 - 07	0
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+1 - 03	2 - 03	1
+1 - 04	2 - 04	0
+1 - 05	2 - 05	0
+1 - 06	2 - 06	0
+1 - 07	2 - 07	0
+
+/*
+B. "Natural" examples of subqueries without grouping that
+cannot be flattened into semijoin.
+*/
+explain
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+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	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+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	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
 a1	a2
+1 - 00	2 - 00
 1 - 01	2 - 01
 1 - 02	2 - 02
 1 - 03	2 - 03
-explain extended
+1 - 04	2 - 04
+1 - 05	2 - 05
+1 - 06	2 - 06
+1 - 07	2 - 07
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+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	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+3	DEPENDENT UNION	t3	ALL	NULL	NULL	NULL	NULL	5	Using where
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+a2
+2 - 01
+2 - 02
+2 - 03
+
+explain
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+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	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+a1
+1 - 02
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+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	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+a1	a2
+1 - 01	2 - 01
+1 - 02	2 - 02
+1 - 03	2 - 03
+
+/* C. Subqueries in the WHERE clause with GROUP BY. */
+explain
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+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	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+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	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+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	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
 select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	6	100.00	Using where
-2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where; Using temporary; Using filesort
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+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	t2	ALL	NULL	NULL	NULL	NULL	5	Using temporary; Using filesort
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+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	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+a1	a2	a3	a4
+
+explain
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+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	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+/*
+D. Subqueries for which materialization is not possible, and the
+optimizer reverts to in-to-exists.
+*/
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	ALL	NULL	NULL	NULL	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	ALL	NULL	NULL	NULL	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	ALL	NULL	NULL	NULL	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	ALL	NULL	NULL	NULL	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+
+
+/* E. Edge cases. */
+
+/* E.1 Both materialization and in_to_exists cannot be off. */
+set @save_optimizer_switch=@@optimizer_switch;
+set @@optimizer_switch = 'materialization=off,in_to_exists=off';
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+ERROR HY000: At least one of the 'in_to_exists' or 'materialization' optimizer_switch flags must be 'on'.
+set @@optimizer_switch = @save_optimizer_switch;
+/* E.2 Outer query without tables, always uses IN-TO-EXISTS. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+'1 - 03' in (select b1 from t2 where b1 > '0')
+1
+/* E.3 Subqueries without tables. */
+explain
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	Using where
 Warnings:
-Note	1003	select `test`.`t1`.`a1` AS `a1`,`test`.`t1`.`a2` AS `a2` from `test`.`t1` where <in_optimizer>((`test`.`t1`.`a1`,`test`.`t1`.`a2`),(`test`.`t1`.`a1`,`test`.`t1`.`a2`) in ( <materialize> (select `test`.`t2`.`b1`,`test`.`t2`.`b2` from `test`.`t2` where (`test`.`t2`.`b1` > '0') group by `test`.`t2`.`b1`,`test`.`t2`.`b2` having (`test`.`t2`.`b2` < '2 - 04') ), <primary_index_lookup>(`test`.`t1`.`a1` in <temporary table> on distinct_key where ((`test`.`t1`.`a1` = `materialized subselect`.`b1`) and (`test`.`t1`.`a2` = `materialized subselect`.`b2`)))))
+Note	1249	Select 2 was reduced during optimization
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+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	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	DEPENDENT UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+a1
+1 - 02
+1 - 03
+/* E.4 optimize_cond detects FALSE where/having clause. */
+explain
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+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	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+/* E.5 opt_sum_query detects no matching min/max row or substitutes MIN/MAX with a const. */
+TODO this test produces wrong result due to missing logic to handle the case
+when JOIN::optimize detects an empty subquery result.
+
+/* E.6 make_join_select detects impossible WHERE. *
+TODO
+/* E.7 constant optimization detects "no matching row in const table". */
+TODO
+/* E.8 Impossible WHERE noticed after reading const tables. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+'1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0')
+0
+
+/* F. UPDATE/DELETE with subqueries. */
+
+TODO
+
+/* 2.2 indexed table access, nullabale columns. */
+call make_t2_indexes();
+
+/* A. Subqueries in the SELECT clause. */
+explain
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i3	it2i1	9	func	2	Using index; Using where; Full scan on NULL key
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+a1	a1 in (select b1 from t2 where b1 > '0')
+1 - 00	0
+1 - 01	1
+1 - 02	1
+1 - 03	1
+1 - 04	0
+1 - 05	0
+1 - 06	0
+1 - 07	0
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i2,it2i3	it2i3	9	func	2	Using index; Using where; Full scan on NULL key
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+1 - 03	2 - 03	1
+1 - 04	2 - 04	0
+1 - 05	2 - 05	0
+1 - 06	2 - 06	0
+1 - 07	2 - 07	0
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i2,it2i3	it2i3	9	func	2	Using index; Using where; Full scan on NULL key
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+1 - 03	2 - 03	1
+1 - 04	2 - 04	0
+1 - 05	2 - 05	0
+1 - 06	2 - 06	0
+1 - 07	2 - 07	0
+
+/*
+B. "Natural" examples of subqueries without grouping that
+cannot be flattened into semijoin.
+*/
+explain
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+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	t2	index_subquery	it2i2	it2i2	9	func	2	Using index
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+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	t2	index_subquery	it2i4,it2i1,it2i2,it2i3	it2i4	18	func,func	1	Using index; Using where
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+a1	a2
+1 - 00	2 - 00
+1 - 01	2 - 01
+1 - 02	2 - 02
+1 - 03	2 - 03
+1 - 04	2 - 04
+1 - 05	2 - 05
+1 - 06	2 - 06
+1 - 07	2 - 07
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+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	t2	ref	it2i2	it2i2	9	func	2	Using index
+3	DEPENDENT UNION	t3	index	NULL	it2i4	27	NULL	5	Using where; Using index
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+a2
+2 - 01
+2 - 02
+2 - 03
+
+explain
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+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	t2	ref	it2i2	it2i2	9	const	1	Using index condition
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+a1
+1 - 02
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+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	t2	index_subquery	it2i4,it2i1,it2i2,it2i3	it2i4	18	func,func	1	Using index; Using where
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+a1	a2
+1 - 01	2 - 01
+1 - 02	2 - 02
+1 - 03	2 - 03
+
+/* C. Subqueries in the WHERE clause with GROUP BY. */
+explain
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+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	t2	index	it2i4,it2i1,it2i3	it2i1	9	NULL	1	Using where; Using index
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+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	t2	index	it2i4,it2i1,it2i3	it2i3	18	NULL	1	Using where; Using index
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
+
+explain
 select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+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	t2	index	it2i4,it2i1,it2i3	it2i3	18	NULL	1	Using where; Using index
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+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	t2	index	NULL	it2i4	27	NULL	1	Using index
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+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	t2	index	NULL	it2i4	27	NULL	1	Using where; Using index
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+a1	a2	a3	a4
+
+explain
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+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	t2	range	it2i4,it2i1,it2i3	it2i4	27	NULL	2	Using where; Using index for group-by
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+/*
+D. Subqueries for which materialization is not possible, and the
+optimizer reverts to in-to-exists.
+*/
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	index_subquery	it2_1024i1,it2_1024i3	it2_1024i3	9	func	1	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	index_subquery	it2_1024i1,it2_1024i2,it2_1024i3	it2_1024i1	9	func	2	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	range	it2_1024i1,it2_1024i3	it2_1024i1	9	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	range	it2_1024i1,it2_1024i3	it2_1024i1	9	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+
+
+/* E. Edge cases. */
+
+/* E.1 Both materialization and in_to_exists cannot be off. */
+set @save_optimizer_switch=@@optimizer_switch;
+set @@optimizer_switch = 'materialization=off,in_to_exists=off';
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+ERROR HY000: At least one of the 'in_to_exists' or 'materialization' optimizer_switch flags must be 'on'.
+set @@optimizer_switch = @save_optimizer_switch;
+/* E.2 Outer query without tables, always uses IN-TO-EXISTS. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i3	it2i1	9	const	2	Using index; Using where
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+'1 - 03' in (select b1 from t2 where b1 > '0')
+1
+/* E.3 Subqueries without tables. */
+explain
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	Using where
+Warnings:
+Note	1249	Select 2 was reduced during optimization
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+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	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	DEPENDENT UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+a1
+1 - 02
+1 - 03
+/* E.4 optimize_cond detects FALSE where/having clause. */
+explain
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+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	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+/* E.5 opt_sum_query detects no matching min/max row or substitutes MIN/MAX with a const. */
+TODO this test produces wrong result due to missing logic to handle the case
+when JOIN::optimize detects an empty subquery result.
+
+/* E.6 make_join_select detects impossible WHERE. *
+TODO
+/* E.7 constant optimization detects "no matching row in const table". */
+TODO
+/* E.8 Impossible WHERE noticed after reading const tables. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+'1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0')
+0
+
+/* F. UPDATE/DELETE with subqueries. */
+
+TODO
+
+/* 2.3 indexed table access, non-nullabale columns. */
+call set_all_columns_not_null();
+
+/* A. Subqueries in the SELECT clause. */
+explain
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i3	it2i4	8	func	1	Using index; Using where
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+a1	a1 in (select b1 from t2 where b1 > '0')
+1 - 00	0
+1 - 01	1
+1 - 02	1
+1 - 03	1
+1 - 04	0
+1 - 05	0
+1 - 06	0
+1 - 07	0
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	DEPENDENT SUBQUERY	t2	ref	it2i4,it2i1,it2i2,it2i3	it2i4	8	func	2	Using where; Using index
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+1 - 03	2 - 03	1
+1 - 04	2 - 04	0
+1 - 05	2 - 05	0
+1 - 06	2 - 06	0
+1 - 07	2 - 07	0
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	
+2	DEPENDENT SUBQUERY	t2	ref	it2i4,it2i1,it2i2,it2i3	it2i4	8	func	2	Using where; Using index
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+1 - 03	2 - 03	1
+1 - 04	2 - 04	0
+1 - 05	2 - 05	0
+1 - 06	2 - 06	0
+1 - 07	2 - 07	0
+
+/*
+B. "Natural" examples of subqueries without grouping that
+cannot be flattened into semijoin.
+*/
+explain
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+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	t2	index_subquery	it2i2	it2i2	8	func	2	Using index
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+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	t2	index_subquery	it2i4,it2i1,it2i2,it2i3	it2i4	16	func,func	1	Using index; Using where
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
 a1	a2
+1 - 00	2 - 00
 1 - 01	2 - 01
 1 - 02	2 - 02
 1 - 03	2 - 03
-delete from t1 where a1 >= '1 - 03';
-1.2.2 Materialization is NOT executable, revert to in-to-exists
+1 - 04	2 - 04
+1 - 05	2 - 05
+1 - 06	2 - 06
+1 - 07	2 - 07
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+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	t2	ref	it2i2	it2i2	8	func	2	Using index
+3	DEPENDENT UNION	t3	index	NULL	it2i4	24	NULL	5	Using where; Using index
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+a2
+2 - 01
+2 - 02
+2 - 03
 
-2. Materialization is OFF, in-to-exists is ON
+explain
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+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	t2	ref	it2i2	it2i2	8	const	1	Using index condition
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+a1
+1 - 02
 
-set @@optimizer_switch='materialization=off,in_to_exists=on';
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+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	t2	index_subquery	it2i4,it2i1,it2i2,it2i3	it2i4	16	func,func	1	Using index; Using where
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+a1	a2
+1 - 01	2 - 01
+1 - 02	2 - 02
+1 - 03	2 - 03
 
-3. Materialization is ON, in-to-exists is OFF
+/* C. Subqueries in the WHERE clause with GROUP BY. */
+explain
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+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	t2	index	it2i4,it2i1,it2i3	it2i1	8	NULL	1	Using where; Using index
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
 
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+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	t2	index	it2i4,it2i1,it2i3	it2i3	16	NULL	1	Using where; Using index
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+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	t2	index	it2i4,it2i1,it2i3	it2i3	16	NULL	1	Using where; Using index
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+1 - 03	2 - 03	3 - 03	3
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+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	t2	index	NULL	it2i4	24	NULL	1	Using index
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+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	t2	index	NULL	it2i4	24	NULL	1	Using where; Using index
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+a1	a2	a3	a4
+
+explain
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+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	t2	range	it2i4,it2i1,it2i3	it2i4	24	NULL	2	Using where; Using index for group-by
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+/*
+D. Subqueries for which materialization is not possible, and the
+optimizer reverts to in-to-exists.
+*/
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	index_subquery	it2_1024i1,it2_1024i3	it2_1024i3	9	func	1	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	index_subquery	it2_1024i1,it2_1024i2,it2_1024i3	it2_1024i1	9	func	2	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	range	it2_1024i1,it2_1024i3	it2_1024i1	9	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	range	it2_1024i1,it2_1024i3	it2_1024i1	9	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+1 - 03x	2 - 03x
+
+
+/* E. Edge cases. */
+
+/* E.1 Both materialization and in_to_exists cannot be off. */
+set @save_optimizer_switch=@@optimizer_switch;
+set @@optimizer_switch = 'materialization=off,in_to_exists=off';
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+ERROR HY000: At least one of the 'in_to_exists' or 'materialization' optimizer_switch flags must be 'on'.
+set @@optimizer_switch = @save_optimizer_switch;
+/* E.2 Outer query without tables, always uses IN-TO-EXISTS. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i3	it2i1	8	const	5	Using index; Using where
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+'1 - 03' in (select b1 from t2 where b1 > '0')
+1
+/* E.3 Subqueries without tables. */
+explain
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	Using where
+Warnings:
+Note	1249	Select 2 was reduced during optimization
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+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	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	DEPENDENT UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+a1
+1 - 02
+1 - 03
+/* E.4 optimize_cond detects FALSE where/having clause. */
+explain
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+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	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+1 - 03
+1 - 04
+1 - 05
+1 - 06
+1 - 07
+/* E.5 opt_sum_query detects no matching min/max row or substitutes MIN/MAX with a const. */
+TODO this test produces wrong result due to missing logic to handle the case
+when JOIN::optimize detects an empty subquery result.
+
+/* E.6 make_join_select detects impossible WHERE. *
+TODO
+/* E.7 constant optimization detects "no matching row in const table". */
+TODO
+/* E.8 Impossible WHERE noticed after reading const tables. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+'1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0')
+0
+
+/* F. UPDATE/DELETE with subqueries. */
+
+TODO
+
+call set_all_columns_nullable();
+/******************************************************************************
+3. Materialization is ON, in-to-exists is OFF, in-to-exists is cheaper.
+******************************************************************************/
 set @@optimizer_switch='materialization=on,in_to_exists=off';
-3.1 Materialization is executable
-3.2 Materialization is NOT executable, revert to in-to-exists
+call delete_materialization_data();
+call make_t1_indexes();
+/* 3.1 non-indexed table access */
+call remove_t2_indexes();
+
+/* A. Subqueries in the SELECT clause. */
+explain
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i1	9	NULL	3	Using index
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+a1	a1 in (select b1 from t2 where b1 > '0')
+1 - 00	0
+1 - 01	1
+1 - 02	1
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	18	NULL	3	Using index
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
 
-4. Edge cases
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	18	NULL	3	Using index
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
 
-4.0 Both materialization and in_to_exists cannot be off
-set @@optimizer_switch='materialization=off,in_to_exists=off';
+/*
+B. "Natural" examples of subqueries without grouping that
+cannot be flattened into semijoin.
+*/
+explain
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	18	NULL	3	Using where; Using index
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	18	NULL	3	Using where; Using index
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+a1	a2
+1 - 00	2 - 00
+1 - 01	2 - 01
+1 - 02	2 - 02
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i2	9	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+3	DEPENDENT UNION	t3	ALL	NULL	NULL	NULL	NULL	5	Using where
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+a2
+2 - 01
+2 - 02
+
+explain
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ref	it1i1,it1i3	it1i1	9	const	1	Using where; Using index
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+a1
+1 - 02
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	18	NULL	3	Using where; Using index
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+a1	a2
+1 - 01	2 - 01
+1 - 02	2 - 02
+
+/* C. Subqueries in the WHERE clause with GROUP BY. */
+explain
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using temporary; Using filesort
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+a1	a2	a3	a4
+
+explain
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+/*
+D. Subqueries for which materialization is not possible, and the
+optimizer reverts to in-to-exists.
+*/
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	ALL	NULL	NULL	NULL	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	ALL	NULL	NULL	NULL	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	ALL	NULL	NULL	NULL	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	ALL	NULL	NULL	NULL	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+
+
+/* E. Edge cases. */
+
+/* E.1 Both materialization and in_to_exists cannot be off. */
+set @save_optimizer_switch=@@optimizer_switch;
+set @@optimizer_switch = 'materialization=off,in_to_exists=off';
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+ERROR HY000: At least one of the 'in_to_exists' or 'materialization' optimizer_switch flags must be 'on'.
+set @@optimizer_switch = @save_optimizer_switch;
+/* E.2 Outer query without tables, always uses IN-TO-EXISTS. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+'1 - 03' in (select b1 from t2 where b1 > '0')
+1
+/* E.3 Subqueries without tables. */
+explain
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i1,it1i2,it1i3	it1i3	18	NULL	3	Using where; Using index
+Warnings:
+Note	1249	Select 2 was reduced during optimization
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i1	9	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	DEPENDENT UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+a1
+1 - 02
+/* E.4 optimize_cond detects FALSE where/having clause. */
+explain
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	18	NULL	3	Using where; Using index
+2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+/* E.5 opt_sum_query detects no matching min/max row or substitutes MIN/MAX with a const. */
+TODO this test produces wrong result due to missing logic to handle the case
+when JOIN::optimize detects an empty subquery result.
+
+/* E.6 make_join_select detects impossible WHERE. *
+TODO
+/* E.7 constant optimization detects "no matching row in const table". */
+TODO
+/* E.8 Impossible WHERE noticed after reading const tables. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	5	Using where
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+'1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0')
+0
+
+/* F. UPDATE/DELETE with subqueries. */
+
+TODO
+
+/* 3.2 indexed table access, nullabale columns. */
+call make_t2_indexes();
+
+/* A. Subqueries in the SELECT clause. */
+explain
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i1	9	NULL	3	Using index
+2	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i1	9	NULL	5	Using where; Using index
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+a1	a1 in (select b1 from t2 where b1 > '0')
+1 - 00	0
+1 - 01	1
+1 - 02	1
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	18	NULL	3	Using index
+2	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i3	18	NULL	5	Using where; Using index
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	18	NULL	3	Using index
+2	SUBQUERY	t2	range	it2i4,it2i1,it2i3	it2i3	9	NULL	4	Using where; Using index
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+
+/*
+B. "Natural" examples of subqueries without grouping that
+cannot be flattened into semijoin.
+*/
+explain
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	18	NULL	3	Using where; Using index
+2	SUBQUERY	t2	index	NULL	it2i2	9	NULL	5	Using index
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	18	NULL	3	Using where; Using index
+2	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i3	18	NULL	5	Using where; Using index
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+a1	a2
+1 - 00	2 - 00
+1 - 01	2 - 01
+1 - 02	2 - 02
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i2	9	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	ref	it2i2	it2i2	9	func	2	Using index
+3	DEPENDENT UNION	t3	index	NULL	it2i4	27	NULL	5	Using where; Using index
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+a2
+2 - 01
+2 - 02
+
+explain
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ref	it1i1,it1i3	it1i1	9	const	1	Using where; Using index
+2	SUBQUERY	t2	ref	it2i2	it2i2	9	const	1	Using index condition
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+a1
+1 - 02
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	18	NULL	3	Using where; Using index
+2	SUBQUERY	t2	index	NULL	it2i4	27	NULL	5	Using index
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+a1	a2
+1 - 01	2 - 01
+1 - 02	2 - 02
+
+/* C. Subqueries in the WHERE clause with GROUP BY. */
+explain
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i1	9	NULL	5	Using where; Using index
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i3	18	NULL	5	Using where; Using index
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i3	18	NULL	5	Using where; Using index
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	range	NULL	it2i4	27	NULL	6	Using index for group-by
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	range	NULL	it2i4	27	NULL	6	Using where; Using index for group-by
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+a1	a2	a3	a4
+
+explain
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	range	it2i4,it2i1,it2i3	it2i4	27	NULL	2	Using where; Using index for group-by
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+/*
+D. Subqueries for which materialization is not possible, and the
+optimizer reverts to in-to-exists.
+*/
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	index_subquery	it2_1024i1,it2_1024i3	it2_1024i3	9	func	1	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	index_subquery	it2_1024i1,it2_1024i2,it2_1024i3	it2_1024i1	9	func	2	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	range	it2_1024i1,it2_1024i3	it2_1024i1	9	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	range	it2_1024i1,it2_1024i3	it2_1024i1	9	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+
+
+/* E. Edge cases. */
+
+/* E.1 Both materialization and in_to_exists cannot be off. */
+set @save_optimizer_switch=@@optimizer_switch;
+set @@optimizer_switch = 'materialization=off,in_to_exists=off';
 select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
 ERROR HY000: At least one of the 'in_to_exists' or 'materialization' optimizer_switch flags must be 'on'.
-4.1 Outer query with no tables
-4.2 Subquery with no tables
-4.3 optimize_cond detects FALSE where/having clause
-4.4 opt_sum_query detects no matching min/max row or substitutes MIN/MAX with a const
-4.4 make_join_select detects impossible WHERE
-4.5 constant optimization detects "no matching row in const table"
-5. UPDATE/DELETE with subqueries
-drop table t1, t2, t3, t1i, t2i, t3i;
+set @@optimizer_switch = @save_optimizer_switch;
+/* E.2 Outer query without tables, always uses IN-TO-EXISTS. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i3	it2i1	9	const	2	Using index; Using where
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+'1 - 03' in (select b1 from t2 where b1 > '0')
+1
+/* E.3 Subqueries without tables. */
+explain
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i1,it1i2,it1i3	it1i3	18	NULL	3	Using where; Using index
+Warnings:
+Note	1249	Select 2 was reduced during optimization
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i1	9	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	DEPENDENT UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+a1
+1 - 02
+/* E.4 optimize_cond detects FALSE where/having clause. */
+explain
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	18	NULL	3	Using where; Using index
+2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+/* E.5 opt_sum_query detects no matching min/max row or substitutes MIN/MAX with a const. */
+TODO this test produces wrong result due to missing logic to handle the case
+when JOIN::optimize detects an empty subquery result.
+
+/* E.6 make_join_select detects impossible WHERE. *
+TODO
+/* E.7 constant optimization detects "no matching row in const table". */
+TODO
+/* E.8 Impossible WHERE noticed after reading const tables. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+'1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0')
+0
+
+/* F. UPDATE/DELETE with subqueries. */
+
+TODO
+
+/* 3.3 indexed table access, non-nullabale columns. */
+call set_all_columns_not_null();
+
+/* A. Subqueries in the SELECT clause. */
+explain
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i1	8	NULL	3	Using index
+2	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i1	8	NULL	5	Using where; Using index
+select a1, a1 in (select b1 from t2 where b1 > '0') from t1;
+a1	a1 in (select b1 from t2 where b1 > '0')
+1 - 00	0
+1 - 01	1
+1 - 02	1
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	16	NULL	3	Using index
+2	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i3	16	NULL	5	Using where; Using index
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+
+explain
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	16	NULL	3	Using index
+2	SUBQUERY	t2	range	it2i4,it2i1,it2i3	it2i3	8	NULL	4	Using where; Using index
+select a1, a2, (a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9') from t1;
+a1	a2	(a1, a2) in (select b1, b2 from t2 where b1 > '0' and b1 < '9')
+1 - 00	2 - 00	0
+1 - 01	2 - 01	1
+1 - 02	2 - 02	1
+
+/*
+B. "Natural" examples of subqueries without grouping that
+cannot be flattened into semijoin.
+*/
+explain
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	16	NULL	3	Using where; Using index
+2	SUBQUERY	t2	index	NULL	it2i2	8	NULL	5	Using index
+select a1 from t1 where a1 in (select b2 from t2) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	16	NULL	3	Using where; Using index
+2	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i3	16	NULL	5	Using where; Using index
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0') or a2 < '9';
+a1	a2
+1 - 00	2 - 00
+1 - 01	2 - 01
+1 - 02	2 - 02
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i2	8	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	t2	ref	it2i2	it2i2	8	func	2	Using index
+3	DEPENDENT UNION	t3	index	NULL	it2i4	24	NULL	5	Using where; Using index
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a2 from t1 where a2 in (select b2 from t2 UNION select b3 from t2 as t3);
+a2
+2 - 01
+2 - 02
+
+explain
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ref	it1i1,it1i3	it1i1	8	const	1	Using where; Using index
+2	SUBQUERY	t2	ref	it2i2	it2i2	8	const	1	Using index condition
+select a1 from t1 where a1 = '1 - 02' and a1 in (select max(b1) from t2 where b2 = '2 - 02');
+a1
+1 - 02
+
+explain
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i3	16	NULL	3	Using where; Using index
+2	SUBQUERY	t2	index	NULL	it2i4	24	NULL	5	Using index
+select a1, a2 from t1 where (a1, a2) in (select b1, b2 from t2 order by b3);
+a1	a2
+1 - 01	2 - 01
+1 - 02	2 - 02
+
+/* C. Subqueries in the WHERE clause with GROUP BY. */
+explain
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i1	8	NULL	5	Using where; Using index
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i3	16	NULL	5	Using where; Using index
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	index	it2i4,it2i1,it2i3	it2i3	16	NULL	5	Using where; Using index
+select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+1 - 02	2 - 02	3 - 02	2
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	range	NULL	it2i4	24	NULL	6	Using index for group-by
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 group by b1, b2, b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+explain
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	range	NULL	it2i4	24	NULL	6	Using where; Using index for group-by
+select * from t1 where (a1, a2, a3) in (select b1, b2, b3 from t2 where b3 = '3 - 02' group by b1, b2);
+a1	a2	a3	a4
+
+explain
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	SUBQUERY	t2	range	it2i4,it2i1,it2i3	it2i4	24	NULL	2	Using where; Using index for group-by
+select * from t1 where (a1,a2,a3) in (select b1,b2,b3 from t2 where b1 = '1 - 01' group by b1,b2,b3);
+a1	a2	a3	a4
+1 - 01	2 - 01	3 - 01	1
+
+/*
+D. Subqueries for which materialization is not possible, and the
+optimizer reverts to in-to-exists.
+*/
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	index_subquery	it2_1024i1,it2_1024i3	it2_1024i3	9	func	1	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select b1 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	index_subquery	it2_1024i1,it2_1024i2,it2_1024i3	it2_1024i1	9	func	2	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select b1, b2 from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+
+explain
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	range	it2_1024i1,it2_1024i3	it2_1024i1	9	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where a1 in (select substring(b1,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+explain
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	it1_1024i2	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2_1024	range	it2_1024i1,it2_1024i3	it2_1024i1	9	NULL	4	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,a2) in (select substring(b1,1,1024), substring(b2,1,1024) from t2_1024 where b1 > '0') or a2 < '9';
+left(a1,7)	left(a2,7)
+1 - 00x	2 - 00x
+1 - 01x	2 - 01x
+
+
+/* E. Edge cases. */
+
+/* E.1 Both materialization and in_to_exists cannot be off. */
+set @save_optimizer_switch=@@optimizer_switch;
+set @@optimizer_switch = 'materialization=off,in_to_exists=off';
+select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
+ERROR HY000: At least one of the 'in_to_exists' or 'materialization' optimizer_switch flags must be 'on'.
+set @@optimizer_switch = @save_optimizer_switch;
+/* E.2 Outer query without tables, always uses IN-TO-EXISTS. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	t2	index_subquery	it2i4,it2i1,it2i3	it2i1	8	const	5	Using index; Using where
+select '1 - 03' in (select b1 from t2 where b1 > '0');
+'1 - 03' in (select b1 from t2 where b1 > '0')
+1
+/* E.3 Subqueries without tables. */
+explain
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i1,it1i2,it1i3	it1i3	16	NULL	3	Using where; Using index
+Warnings:
+Note	1249	Select 2 was reduced during optimization
+select a1 from t1 where a1 in (select '1 - 03') or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+UNION subqueries are currently limited to only use IN-TO-EXISTS.
+explain
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	it1i1	8	NULL	3	Using where; Using index
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	DEPENDENT UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+select a1 from t1 where a1 in (select '1 - 03' UNION select '1 - 02');
+a1
+1 - 02
+/* E.4 optimize_cond detects FALSE where/having clause. */
+explain
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	it1i2	it1i3	16	NULL	3	Using where; Using index
+2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+select a1 from t1 where a1 in (select b1 from t2 where b1 = b2 and b2 = '1 - 03' and b1 = '1 - 02' ) or a2 < '9';
+a1
+1 - 00
+1 - 01
+1 - 02
+/* E.5 opt_sum_query detects no matching min/max row or substitutes MIN/MAX with a const. */
+TODO this test produces wrong result due to missing logic to handle the case
+when JOIN::optimize detects an empty subquery result.
+
+/* E.6 make_join_select detects impossible WHERE. *
+TODO
+/* E.7 constant optimization detects "no matching row in const table". */
+TODO
+/* E.8 Impossible WHERE noticed after reading const tables. */
+explain
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+select '1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0');
+'1 - 03' in (select b1 from t2 where b1 > '0' and b1 < '0')
+0
+
+/* F. UPDATE/DELETE with subqueries. */
+
+TODO
+
+call set_all_columns_nullable();
+drop procedure make_t1_indexes;
+drop procedure make_t2_indexes;
+drop procedure remove_t1_indexes;
+drop procedure remove_t2_indexes;
+drop procedure add_materialization_data;
+drop procedure delete_materialization_data;
+drop procedure set_all_columns_not_null;
+drop procedure set_all_columns_nullable;
+drop table t1, t2, t1_1024, t2_1024;
diff --git a/mysql-test/t/subselect_mat.test b/mysql-test/t/subselect_mat.test
index 1c2869c628a..0b3a89336cc 100644
--- a/mysql-test/t/subselect_mat.test
+++ b/mysql-test/t/subselect_mat.test
@@ -48,7 +48,7 @@ insert into t2i select * from t2;
 insert into t3i select * from t3;
 
 # force the use of materialization
-set @@optimizer_switch='semijoin=off';
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
 
 /******************************************************************************
 * Simple tests.
@@ -111,22 +111,22 @@ 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 @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=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,materialization=off';
+set @@optimizer_switch='materialization=off,in_to_exists=on,semijoin=on';
 execute st1;
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=on';
 execute st1;
 
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch='materialization=off,in_to_exists=on,semijoin=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='materialization=on,in_to_exists=off,semijoin=off';
 execute st1;
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch='materialization=off,in_to_exists=on,semijoin=on';
 execute st1;
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
 
 # materialize the result of ORDER BY
 # non-indexed fields
@@ -327,7 +327,7 @@ select * from t1 order by (select col from columns limit 1);
   Test that BLOBs are not materialized (except when arguments of some functions).
 */
 # force materialization to be always considered
-set @@optimizer_switch='semijoin=off';
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
 set @prefix_len = 6;
 
 # BLOB == 16 (small blobs that could be stored in HEAP tables)
@@ -680,7 +680,7 @@ insert into t2bit values (b'001', b'101');
 insert into t2bit values (b'010', b'110');
 insert into t2bit values (b'110', b'111');
 
-set @@optimizer_switch='semijoin=off';
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
 
 explain extended select bin(a1), bin(a2)
 from t1bit
@@ -718,7 +718,7 @@ drop table t1, t2, t3, t1i, t2i, t3i, columns;
 /******************************************************************************
 * Test the cache of the left operand of IN.
 ******************************************************************************/
-set @@optimizer_switch='semijoin=off';
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
 
 # Test that default values of Cached_item are not used for comparison
 create table t1 (s1 int);
@@ -812,23 +812,28 @@ drop table t2;
 create table t1 (a1 int key);
 create table t2 (b1 int);
 insert into t1 values (5);
-
+-- echo Only the last query returns correct result. Filed as BUG#40037.
 # Query with group by, executed via materialization
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
 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 @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch='materialization=off,in_to_exists=on,semijoin=off';
 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='materialization=on,in_to_exists=off,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 via IN=>EXISTS
+set @@optimizer_switch='materialization=off,in_to_exists=on,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
+# This is the only correct result of all five queries. This difference is
 # filed as BUG#40037.
-set @@optimizer_switch='default,materialization=off';
+set @@optimizer_switch='materialization=off,in_to_exists=off,semijoin=on';
 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);
 drop table t1,t2;
@@ -840,7 +845,7 @@ create table t1 (a char(2), b varchar(10));
 insert into t1 values ('a',  'aaa');
 insert into t1 values ('aa', 'aaaa');
 
-set @@optimizer_switch='default,semijoin=off';
+set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';
 explain select a,b from t1 where b in (select a from t1);
 select a,b from t1 where b in (select a from t1);
 prepare st1 from "select a,b from t1 where b in (select a from t1)";
@@ -861,7 +866,7 @@ CREATE TABLE t2 LIKE t1;
 INSERT INTO t2 VALUES (1, 1.789);
 INSERT INTO t2 VALUES (13, 1.454);
 
-SET @@optimizer_switch='default,semijoin=on,materialization=on';
+SET @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=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);
 
@@ -883,7 +888,7 @@ 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 @@optimizer_switch='default,semijoin=on,materialization=on';
+SET @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=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);
@@ -900,7 +905,7 @@ create table t3(i int);
 insert into t3 values (1), (2), (3), (4), (5), (6), (7), (8), (9), (10);
 select * from t1 where t1.i in (select t2.i from t2 join t3 where t2.i + t3.i = 5);
 set @save_optimizer_switch=@@optimizer_switch;
-set session optimizer_switch='materialization=off';
+set session optimizer_switch='materialization=off,in_to_exists=on';
 select * from t1 where t1.i in (select t2.i from t2 join t3 where t2.i + t3.i = 5);
 set session optimizer_switch=@save_optimizer_switch;
 drop table t1, t2, t3;
diff --git a/mysql-test/t/subselect_mat_cost.test b/mysql-test/t/subselect_mat_cost.test
index 702eac508d6..a268322dc5f 100644
--- a/mysql-test/t/subselect_mat_cost.test
+++ b/mysql-test/t/subselect_mat_cost.test
@@ -4,136 +4,200 @@
 #
 
 --disable_warnings
-drop table if exists t1, t2, t3, t1i, t2i, t3i;
+drop table if exists t1, t2, t1_1024, t2_1024;
+drop procedure if exists make_t1_indexes;
+drop procedure if exists make_t2_indexes;
+drop procedure if exists remove_t1_indexes;
+drop procedure if exists remove_t2_indexes;
+drop procedure if exists add_materialization_data;
+drop procedure if exists delete_materialization_data;
+drop procedure if exists set_all_columns_not_null;
+drop procedure if exists set_all_columns_nullable;
 --enable_warnings
 
-create table t1 (a1 char(8), a2 char(8));
-create table t2 (b1 char(8), b2 char(8));
-create table t3 (c1 char(8), c2 char(8));
-
---echo Unindexed tables
-insert into t1 values ('1 - 00', '2 - 00');
-insert into t1 values ('1 - 01', '2 - 01');
-insert into t1 values ('1 - 02', '2 - 02');
-
-insert into t2 values ('1 - 01', '2 - 01');
-insert into t2 values ('1 - 01', '2 - 01');     
-insert into t2 values ('1 - 02', '2 - 02');
-insert into t2 values ('1 - 02', '2 - 02');
-insert into t2 values ('1 - 03', '2 - 03');
-
-insert into t3 values ('1 - 01', '2 - 01');
-insert into t3 values ('1 - 02', '2 - 02');
-insert into t3 values ('1 - 03', '2 - 03');
-insert into t3 values ('1 - 04', '2 - 04');
-
---echo Indexed tables
-create table t1i (a1 char(8), a2 char(8));
-create table t2i (b1 char(8), b2 char(8));
-create table t3i (c1 char(8), c2 char(8));
-create index it1i1 on t1i (a1);
-create index it1i2 on t1i (a2);
-create index it1i3 on t1i (a1, a2);
-
-create index it2i1 on t2i (b1);
-create index it2i2 on t2i (b2);
-create index it2i3 on t2i (b1, b2);
-
-create index it3i1 on t3i (c1);
-create index it3i2 on t3i (c2);
-create index it3i3 on t3i (c1, c2);
-
-insert into t1i select * from t1;
-insert into t2i select * from t2;
-insert into t3i select * from t3;
-
---echo 
---echo 1. Both materialization and in-to-exists are possible to execute
---echo 
+create table t1 (a1 char(8), a2 char(8), a3 char(8), a4 int);
+insert into t1 values ('1 - 00', '2 - 00', '3 - 00', 0);
+insert into t1 values ('1 - 01', '2 - 01', '3 - 01', 1);
+insert into t1 values ('1 - 02', '2 - 02', '3 - 02', 2);
+
+create table t2 (b1 char(8), b2 char(8), b3 char(8), b4 int);
+insert into t2 values ('1 - 01', '2 - 01', '3 - 01', 1);
+insert into t2 values ('1 - 01', '2 - 01', '3 - 02', 2);
+insert into t2 values ('1 - 02', '2 - 02', '3 - 03', 3);
+insert into t2 values ('1 - 02', '2 - 02', '3 - 04', 4);
+insert into t2 values ('1 - 03', '2 - 03', '3 - 05', 5);
+
+create table t1_1024 (a1 blob(1024), a2 blob(1024));
+insert into t1_1024 values (concat('1 - 00', repeat('x', 1018)), concat('2 - 00', repeat('x', 1018)));
+insert into t1_1024 values (concat('1 - 01', repeat('x', 1018)), concat('2 - 01', repeat('x', 1018)));
+
+create table t2_1024 (b1 blob(1024), b2 blob(1024));
+insert into t2_1024 values (concat('1 - 01', repeat('x', 1018)), concat('2 - 01', repeat('x', 1018)));
+insert into t2_1024 values (concat('1 - 02', repeat('x', 1018)), concat('2 - 02', repeat('x', 1018)));
+insert into t2_1024 values (concat('1 - 03', repeat('x', 1018)), concat('2 - 03', repeat('x', 1018)));
+insert into t2_1024 values (concat('1 - 04', repeat('x', 1018)), concat('2 - 04', repeat('x', 1018)));
+
+delimiter |;
+create procedure make_t1_indexes()
+begin
+  create index it1i1 on t1 (a1);
+  create index it1i2 on t1 (a2);
+  create index it1i3 on t1 (a1, a2);
+  create index it1_1024i1 on t1_1024 (a1(6));
+  create index it1_1024i2 on t1_1024 (a2(6));
+  create index it1_1024i3 on t1_1024 (a1(6), a2(6));
+end|
+
+create procedure make_t2_indexes()
+begin
+  create index it2i1 on t2 (b1);
+  create index it2i2 on t2 (b2);
+  create index it2i3 on t2 (b1, b2);
+  create unique index it2i4 on t2 (b1, b2, b3);
+  create index it2_1024i1 on t2_1024 (b1(6));
+  create index it2_1024i2 on t2_1024 (b2(6));
+  create index it2_1024i3 on t2_1024 (b1(6), b2(6));
+end|
+
+create procedure remove_t1_indexes()
+begin
+  drop index it1i1 on t1;
+  drop index it1i2 on t1;
+  drop index it1i3 on t1;
+  drop index it1_1024i1 on t1_1024;
+  drop index it1_1024i2 on t1_1024;
+  drop index it1_1024i3 on t1_1024;
+end|
+
+create procedure remove_t2_indexes()
+begin
+  drop index it2i1 on t2;
+  drop index it2i2 on t2;
+  drop index it2i3 on t2;
+  drop index it2i4 on t2;
+  drop index it2_1024i1 on t2_1024;
+  drop index it2_1024i2 on t2_1024;
+  drop index it2_1024i3 on t2_1024;
+end|
+
+create procedure add_materialization_data()
+begin
+insert into t1 values ('1 - 03', '2 - 03', '3 - 03', 3);
+insert into t1 values ('1 - 04', '2 - 04', '3 - 04', 4);
+insert into t1 values ('1 - 05', '2 - 05', '3 - 05', 5);
+insert into t1 values ('1 - 06', '2 - 06', '3 - 06', 6);
+insert into t1 values ('1 - 07', '2 - 07', '3 - 07', 7);
+insert into t1_1024 values (concat('1 - 03', repeat('x', 1018)), concat('2 - 03', repeat('x', 1018)));
+end|
+
+create procedure delete_materialization_data()
+begin
+delete from t1 where a1 >= '1 - 03';
+delete from t1_1024 where a1 >= '1 - 03';
+end|
+
+create procedure set_all_columns_not_null()
+begin
+alter table t1 modify a1 char(8) not null, modify a2 char(8) not null, modify a3 char(8) not null;
+alter table t2 modify b1 char(8) not null, modify b2 char(8) not null, modify b3 char(8) not null;
+end|
+
+create procedure set_all_columns_nullable()
+begin
+alter table t1 modify a1 char(8) null, modify a2 char(8) null, modify a3 char(8) null;
+alter table t2 modify b1 char(8) null, modify b2 char(8) null, modify b3 char(8) null;
+end|
+
+delimiter ;|
+-- echo
+
+-- echo /******************************************************************************
+-- echo 1. Both materialization and in-to-exists are ON, make a cost-based choice.
+-- echo ******************************************************************************/
 set @@optimizer_switch='materialization=on,in_to_exists=on';
+-- echo 
+-- echo /* 1.1 In-to-exists is cheaper */
+call make_t1_indexes();
 
---echo 
---echo 1.1 In-to-exists is cheaper
-
-set @@optimizer_switch='semijoin=off';
-explain extended
-select * from t1 where a1 in (select b1 from t2 where b1 > '0');
-select * from t1 where a1 in (select b1 from t2 where b1 > '0');
-explain extended
-select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0');
-select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0');
-
-set @@optimizer_switch='semijoin=on';
-explain extended
-select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
-select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
-explain extended
-select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
-select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
-explain extended
-select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
-select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
-
---echo 
---echo 1.2 Materialization is cheaper
-
---echo 1.2.1 Materialization is executable
-
-insert into t1 values ('1 - 03', '2 - 03');
-insert into t1 values ('1 - 04', '2 - 04');
-insert into t1 values ('1 - 05', '2 - 05');
-
-set @@optimizer_switch='semijoin=off';
-explain extended
-select * from t1 where a1 in (select b1 from t2 where b1 > '0');
-select * from t1 where a1 in (select b1 from t2 where b1 > '0');
-explain extended
-select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0');
-select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0');
-
-set @@optimizer_switch='semijoin=on';
-explain extended
-select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
-select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
-explain extended
-select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
-select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2);
-explain extended
-select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
-select * from t1 where (a1, a2) in (select b1, b2 from t2 where b1 > '0' group by b1, b2 having b2 <  '2 - 04');
+-- echo /* 1.1.1 non-indexed table access */
+-- source include/subselect_mat_cost.inc
 
-delete from t1 where a1 >= '1 - 03';
+-- echo /* 1.1.2 indexed table access, nullabale columns. */
+call make_t2_indexes();
+-- source include/subselect_mat_cost.inc
 
---echo 1.2.2 Materialization is NOT executable, revert to in-to-exists
+-- echo /* 1.1.3 indexed table access, non-nullabale columns. */
+call set_all_columns_not_null();
+-- source include/subselect_mat_cost.inc
+call set_all_columns_nullable();
 
---echo 
---echo 2. Materialization is OFF, in-to-exists is ON
---echo 
-set @@optimizer_switch='materialization=off,in_to_exists=on';
+-- echo 
+-- echo /* 1.2 Materialization is cheaper */
+# make materialization cheaper
+call add_materialization_data();
+call remove_t1_indexes();
 
---echo 
---echo 3. Materialization is ON, in-to-exists is OFF
---echo 
-set @@optimizer_switch='materialization=on,in_to_exists=off';
+-- echo /* 1.2.1 non-indexed table access */
+call remove_t2_indexes();
+-- source include/subselect_mat_cost.inc
+
+-- echo /* 1.2.2 indexed table access, nullabale columns. */
+call make_t2_indexes();
+-- source include/subselect_mat_cost.inc
 
---echo 3.1 Materialization is executable
---echo 3.2 Materialization is NOT executable, revert to in-to-exists
+-- echo /* 1.2.3 indexed table access, non-nullabale columns. */
+call set_all_columns_not_null();
+-- source include/subselect_mat_cost.inc
+call set_all_columns_nullable();
 
---echo 
---echo 4. Edge cases
---echo 
---echo 4.0 Both materialization and in_to_exists cannot be off
-set @@optimizer_switch='materialization=off,in_to_exists=off';
---error ER_ILLEGAL_SUBQUERY_OPTIMIZER_SWITCHES
-select * from t1 where a1 in (select b1 from t2 where b1 > '0' group by b1);
 
---echo 4.1 Outer query with no tables
---echo 4.2 Subquery with no tables
---echo 4.3 optimize_cond detects FALSE where/having clause
---echo 4.4 opt_sum_query detects no matching min/max row or substitutes MIN/MAX with a const
---echo 4.4 make_join_select detects impossible WHERE
---echo 4.5 constant optimization detects "no matching row in const table"
+-- echo /******************************************************************************
+-- echo 2. Materialization is OFF, in-to-exists is ON, materialization is cheaper.
+-- echo ******************************************************************************/
+set @@optimizer_switch='materialization=off,in_to_exists=on';
+
+-- echo /* 2.1 non-indexed table access */
+call remove_t2_indexes();
+-- source include/subselect_mat_cost.inc
+
+-- echo /* 2.2 indexed table access, nullabale columns. */
+call make_t2_indexes();
+-- source include/subselect_mat_cost.inc
 
---echo 5. UPDATE/DELETE with subqueries
+-- echo /* 2.3 indexed table access, non-nullabale columns. */
+call set_all_columns_not_null();
+-- source include/subselect_mat_cost.inc
+call set_all_columns_nullable();
 
-drop table t1, t2, t3, t1i, t2i, t3i;
+
+-- echo /******************************************************************************
+-- echo 3. Materialization is ON, in-to-exists is OFF, in-to-exists is cheaper.
+-- echo ******************************************************************************/
+set @@optimizer_switch='materialization=on,in_to_exists=off';
+# make IN-TO-EXISTS cheaper
+call delete_materialization_data();
+call make_t1_indexes();
+
+-- echo /* 3.1 non-indexed table access */
+call remove_t2_indexes();
+-- source include/subselect_mat_cost.inc
+
+-- echo /* 3.2 indexed table access, nullabale columns. */
+call make_t2_indexes();
+-- source include/subselect_mat_cost.inc
+
+-- echo /* 3.3 indexed table access, non-nullabale columns. */
+call set_all_columns_not_null();
+-- source include/subselect_mat_cost.inc
+call set_all_columns_nullable();
+
+
+drop procedure make_t1_indexes;
+drop procedure make_t2_indexes;
+drop procedure remove_t1_indexes;
+drop procedure remove_t2_indexes;
+drop procedure add_materialization_data;
+drop procedure delete_materialization_data;
+drop procedure set_all_columns_not_null;
+drop procedure set_all_columns_nullable;
+drop table t1, t2, t1_1024, t2_1024;
diff --git a/sql/opt_subselect.cc b/sql/opt_subselect.cc
index 86d7f606212..25d3aa29904 100644
--- a/sql/opt_subselect.cc
+++ b/sql/opt_subselect.cc
@@ -3403,6 +3403,19 @@ int rewrite_to_index_subquery_engine(JOIN *join)
   /*
     is this simple IN subquery?
   */
+  /* TODO: In order to use these more efficient subquery engines in more cases,
+     the following problems need to be solved:
+     - the code that removes GROUP BY (group_list), also adds an ORDER BY
+       (order), thus GROUP BY queries (almost?) never pass through this branch.
+       Solution: remove the test below '!join->order', because we remove the
+       ORDER clase for subqueries anyway.
+     - in order to set a more efficient engine, the optimizer needs to both
+       decide to remove GROUP BY, *and* select one of the JT_[EQ_]REF[_OR_NULL]
+       access methods, *and* loose scan should be more expensive or
+       inapliccable. When is that possible?
+     - Consider expanding the applicability of this rewrite for loose scan
+       for group by queries.
+  */
   if (!join->group_list && !join->order &&
       join->unit->item && 
       join->unit->item->substype() == Item_subselect::IN_SUBS &&
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index ee99f98c1ea..4e5dc9074f2 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -19372,12 +19372,6 @@ int JOIN::reoptimize(Item *added_where, table_map join_tables,
   DYNAMIC_ARRAY added_keyuse;
   SARGABLE_PARAM *sargables= 0; /* Used only as a dummy parameter. */
 
-  if (my_init_dynamic_array(&added_keyuse, sizeof(KEYUSE), 20, 64))
-  {
-    delete_dynamic(&added_keyuse);
-    return 1;
-  }
-
   /* Re-run the REF optimizer to take into account the new conditions. */
   if (update_ref_and_keys(thd, &added_keyuse, join_tab, tables, added_where,
                           ~outer_join, select_lex, &sargables))