MDEV-537 Make multi-column non-top level subqueries to be executed via index...

MDEV-537 Make multi-column non-top level subqueries to be executed via index (index/unique subquery)
           instead of single_select_engine

This task changes the IN-EXISTS rewrite for multi-column subqueries
"(a, b) IN (select b, c ...)" to work in the same way as for
single-column subqueries "a IN (select b ...) with respect to the
injection of NULL-rejecting predicates.
 
More specifically, the method
Item_in_subselect::create_row_in_to_exists_cond()
adds Item_is_not_null_test and Item_func_trig_cond only if the left
IN operand can be NULL. Not having these predicates when not necessary,
makes it possible to rewrite the subquery into a "unique_subquery" or
"index_subquery" when there is a suitable index on the only
subquery table.

mysql-test/r/derived_view.result

@@ -1468,14 +1468,14 @@ WHERE (t2.a ,t1.b) NOT IN (SELECT DISTINCT c,a  FROM t3 t);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where; Using join buffer (flat, BNL join)
-2	DEPENDENT SUBQUERY	t	eq_ref	PRIMARY,c	PRIMARY	4	func	1	Using where
+2	DEPENDENT SUBQUERY	t	unique_subquery	PRIMARY,c	PRIMARY	4	func	1	Using where
 EXPLAIN 
 SELECT * FROM t1 , t2
 WHERE (t2.a ,t1.b) NOT IN (SELECT DISTINCT c,a  FROM (SELECT * FROM t3) t);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where; Using join buffer (flat, BNL join)
-2	DEPENDENT SUBQUERY	t3	eq_ref	PRIMARY,c	PRIMARY	4	func	1	Using where
+2	DEPENDENT SUBQUERY	t3	unique_subquery	PRIMARY,c	PRIMARY	4	func	1	Using where
 SELECT * FROM t1 , t2
 WHERE (t2.a ,t1.b) NOT IN (SELECT DISTINCT c,a  FROM (SELECT * FROM t3) t);
 b	a

mysql-test/r/subselect.result

@@ -2966,7 +2966,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	100.00	
 2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	9	100.00	Using where
 Warnings:
-Note	1003	select `test`.`t1`.`one` AS `one`,`test`.`t1`.`two` AS `two`,<expr_cache><`test`.`t1`.`one`,`test`.`t1`.`two`>(<in_optimizer>((`test`.`t1`.`one`,`test`.`t1`.`two`),<exists>(select `test`.`t2`.`one`,`test`.`t2`.`two` from `test`.`t2` where ((`test`.`t2`.`flag` = '0') and trigcond(((<cache>(`test`.`t1`.`one`) = `test`.`t2`.`one`) or isnull(`test`.`t2`.`one`))) and trigcond(((<cache>(`test`.`t1`.`two`) = `test`.`t2`.`two`) or isnull(`test`.`t2`.`two`)))) having (trigcond(<is_not_null_test>(`test`.`t2`.`one`)) and trigcond(<is_not_null_test>(`test`.`t2`.`two`)))))) AS `test` from `test`.`t1`
+Note	1003	select `test`.`t1`.`one` AS `one`,`test`.`t1`.`two` AS `two`,<expr_cache><`test`.`t1`.`one`,`test`.`t1`.`two`>(<in_optimizer>((`test`.`t1`.`one`,`test`.`t1`.`two`),<exists>(select `test`.`t2`.`one`,`test`.`t2`.`two` from `test`.`t2` where ((`test`.`t2`.`flag` = '0') and trigcond(trigcond(((<cache>(`test`.`t1`.`one`) = `test`.`t2`.`one`) or isnull(`test`.`t2`.`one`)))) and trigcond(trigcond(((<cache>(`test`.`t1`.`two`) = `test`.`t2`.`two`) or isnull(`test`.`t2`.`two`))))) having (trigcond(<is_not_null_test>(`test`.`t2`.`one`)) and trigcond(<is_not_null_test>(`test`.`t2`.`two`)))))) AS `test` from `test`.`t1`
 explain extended SELECT one,two from t1 where ROW(one,two) IN (SELECT one,two FROM t2 WHERE flag = 'N');
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	100.00	
@@ -2979,7 +2979,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	100.00	
 2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	9	100.00	Using where
 Warnings:
-Note	1003	select `test`.`t1`.`one` AS `one`,`test`.`t1`.`two` AS `two`,<expr_cache><`test`.`t1`.`one`,`test`.`t1`.`two`>(<in_optimizer>((`test`.`t1`.`one`,`test`.`t1`.`two`),<exists>(select `test`.`t2`.`one`,`test`.`t2`.`two` from `test`.`t2` where ((`test`.`t2`.`flag` = '0') and trigcond(((<cache>(`test`.`t1`.`one`) = `test`.`t2`.`one`) or isnull(`test`.`t2`.`one`))) and trigcond(((<cache>(`test`.`t1`.`two`) = `test`.`t2`.`two`) or isnull(`test`.`t2`.`two`)))) having (trigcond(<is_not_null_test>(`test`.`t2`.`one`)) and trigcond(<is_not_null_test>(`test`.`t2`.`two`)))))) AS `test` from `test`.`t1`
+Note	1003	select `test`.`t1`.`one` AS `one`,`test`.`t1`.`two` AS `two`,<expr_cache><`test`.`t1`.`one`,`test`.`t1`.`two`>(<in_optimizer>((`test`.`t1`.`one`,`test`.`t1`.`two`),<exists>(select `test`.`t2`.`one`,`test`.`t2`.`two` from `test`.`t2` where ((`test`.`t2`.`flag` = '0') and trigcond(trigcond(((<cache>(`test`.`t1`.`one`) = `test`.`t2`.`one`) or isnull(`test`.`t2`.`one`)))) and trigcond(trigcond(((<cache>(`test`.`t1`.`two`) = `test`.`t2`.`two`) or isnull(`test`.`t2`.`two`))))) having (trigcond(<is_not_null_test>(`test`.`t2`.`one`)) and trigcond(<is_not_null_test>(`test`.`t2`.`two`)))))) AS `test` from `test`.`t1`
 DROP TABLE t1,t2;
 set optimizer_switch=@tmp11867_optimizer_switch;
 CREATE TABLE t1 (a char(5), b char(5));

mysql-test/r/subselect3.result

@@ -252,7 +252,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 2	DEPENDENT SUBQUERY	t1	index_subquery	a	a	5	func	2	100.00	Using where; Full scan on NULL key
 Warnings:
 Note	1276	Field or reference 'test.t2.oref' of SELECT #2 was resolved in SELECT #1
-Note	1003	select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t2`.`oref` AS `oref`,<expr_cache><`test`.`t2`.`a`,`test`.`t2`.`b`,`test`.`t2`.`oref`>(<in_optimizer>((`test`.`t2`.`a`,`test`.`t2`.`b`),<exists>(<index_lookup>(<cache>(`test`.`t2`.`a`) in t1 on a checking NULL where ((`test`.`t1`.`c` = `test`.`t2`.`oref`) and trigcond(((<cache>(`test`.`t2`.`a`) = `test`.`t1`.`a`) or isnull(`test`.`t1`.`a`))) and trigcond(((<cache>(`test`.`t2`.`b`) = `test`.`t1`.`b`) or isnull(`test`.`t1`.`b`)))) having (trigcond(<is_not_null_test>(`test`.`t1`.`a`)) and trigcond(<is_not_null_test>(`test`.`t1`.`b`))))))) AS `Z` from `test`.`t2`
+Note	1003	select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t2`.`oref` AS `oref`,<expr_cache><`test`.`t2`.`a`,`test`.`t2`.`b`,`test`.`t2`.`oref`>(<in_optimizer>((`test`.`t2`.`a`,`test`.`t2`.`b`),<exists>(<index_lookup>(<cache>(`test`.`t2`.`a`) in t1 on a checking NULL where ((`test`.`t1`.`c` = `test`.`t2`.`oref`) and trigcond(trigcond(((<cache>(`test`.`t2`.`a`) = `test`.`t1`.`a`) or isnull(`test`.`t1`.`a`)))) and trigcond(trigcond(((<cache>(`test`.`t2`.`b`) = `test`.`t1`.`b`) or isnull(`test`.`t1`.`b`))))) having (trigcond(<is_not_null_test>(`test`.`t1`.`a`)) and trigcond(<is_not_null_test>(`test`.`t1`.`b`))))))) AS `Z` from `test`.`t2`
 select a,b, oref, (a,b) in (select a,b from t1 where c=t2.oref) Z from t2;
 a	b	oref	Z
 NULL	1	100	0
@@ -269,7 +269,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 2	DEPENDENT SUBQUERY	t4	ALL	NULL	NULL	NULL	NULL	100	100.00	Using where; Using join buffer (flat, BNL join)
 Warnings:
 Note	1276	Field or reference 'test.t2.oref' of SELECT #2 was resolved in SELECT #1
-Note	1003	select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t2`.`oref` AS `oref`,<expr_cache><`test`.`t2`.`a`,`test`.`t2`.`b`,`test`.`t2`.`oref`>(<in_optimizer>((`test`.`t2`.`a`,`test`.`t2`.`b`),<exists>(select `test`.`t1`.`a`,`test`.`t1`.`b` from `test`.`t1` join `test`.`t4` where ((`test`.`t1`.`c` = `test`.`t2`.`oref`) and trigcond(((<cache>(`test`.`t2`.`a`) = `test`.`t1`.`a`) or isnull(`test`.`t1`.`a`))) and trigcond(((<cache>(`test`.`t2`.`b`) = `test`.`t1`.`b`) or isnull(`test`.`t1`.`b`)))) having (trigcond(<is_not_null_test>(`test`.`t1`.`a`)) and trigcond(<is_not_null_test>(`test`.`t1`.`b`)))))) AS `Z` from `test`.`t2`
+Note	1003	select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t2`.`oref` AS `oref`,<expr_cache><`test`.`t2`.`a`,`test`.`t2`.`b`,`test`.`t2`.`oref`>(<in_optimizer>((`test`.`t2`.`a`,`test`.`t2`.`b`),<exists>(select `test`.`t1`.`a`,`test`.`t1`.`b` from `test`.`t1` join `test`.`t4` where ((`test`.`t1`.`c` = `test`.`t2`.`oref`) and trigcond(trigcond(((<cache>(`test`.`t2`.`a`) = `test`.`t1`.`a`) or isnull(`test`.`t1`.`a`)))) and trigcond(trigcond(((<cache>(`test`.`t2`.`b`) = `test`.`t1`.`b`) or isnull(`test`.`t1`.`b`))))) having (trigcond(<is_not_null_test>(`test`.`t1`.`a`)) and trigcond(<is_not_null_test>(`test`.`t1`.`b`)))))) AS `Z` from `test`.`t2`
 select a,b, oref, 
 (a,b) in (select a,b from t1,t4 where c=t2.oref) Z 
 from t2;
@@ -314,7 +314,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 2	DEPENDENT SUBQUERY	t1	index_subquery	idx	idx	5	func	4	100.00	Using where; Full scan on NULL key
 Warnings:
 Note	1276	Field or reference 'test.t2.oref' of SELECT #2 was resolved in SELECT #1
-Note	1003	select `test`.`t2`.`oref` AS `oref`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,<expr_cache><`test`.`t2`.`a`,`test`.`t2`.`b`,`test`.`t2`.`oref`>(<in_optimizer>((`test`.`t2`.`a`,`test`.`t2`.`b`),<exists>(<index_lookup>(<cache>(`test`.`t2`.`a`) in t1 on idx checking NULL where ((`test`.`t1`.`oref` = `test`.`t2`.`oref`) and trigcond(((<cache>(`test`.`t2`.`a`) = `test`.`t1`.`ie1`) or isnull(`test`.`t1`.`ie1`))) and trigcond(((<cache>(`test`.`t2`.`b`) = `test`.`t1`.`ie2`) or isnull(`test`.`t1`.`ie2`)))) having (trigcond(<is_not_null_test>(`test`.`t1`.`ie1`)) and trigcond(<is_not_null_test>(`test`.`t1`.`ie2`))))))) AS `Z` from `test`.`t2` where ((`test`.`t2`.`b` = 10) and (`test`.`t2`.`a` = 10))
+Note	1003	select `test`.`t2`.`oref` AS `oref`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,<expr_cache><`test`.`t2`.`a`,`test`.`t2`.`b`,`test`.`t2`.`oref`>(<in_optimizer>((`test`.`t2`.`a`,`test`.`t2`.`b`),<exists>(<index_lookup>(<cache>(`test`.`t2`.`a`) in t1 on idx checking NULL where ((`test`.`t1`.`oref` = `test`.`t2`.`oref`) and trigcond(trigcond(((<cache>(`test`.`t2`.`a`) = `test`.`t1`.`ie1`) or isnull(`test`.`t1`.`ie1`)))) and trigcond(trigcond(((<cache>(`test`.`t2`.`b`) = `test`.`t1`.`ie2`) or isnull(`test`.`t1`.`ie2`))))) having (trigcond(<is_not_null_test>(`test`.`t1`.`ie1`)) and trigcond(<is_not_null_test>(`test`.`t1`.`ie2`))))))) AS `Z` from `test`.`t2` where ((`test`.`t2`.`b` = 10) and (`test`.`t2`.`a` = 10))
 drop table t1, t2;
 create table t1 (oref char(4), grp int, ie int);
 insert into t1 (oref, grp, ie) values
@@ -584,7 +584,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 2	DEPENDENT SUBQUERY	t1	index_subquery	idx	idx	5	func	4	100.00	Using where; Full scan on NULL key
 Warnings:
 Note	1276	Field or reference 'test.t2.oref' of SELECT #2 was resolved in SELECT #1
-Note	1003	select `test`.`t2`.`oref` AS `oref`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,<expr_cache><`test`.`t2`.`a`,`test`.`t2`.`b`,`test`.`t2`.`oref`>(<in_optimizer>((`test`.`t2`.`a`,`test`.`t2`.`b`),<exists>(<index_lookup>(<cache>(`test`.`t2`.`a`) in t1 on idx checking NULL where ((`test`.`t1`.`oref` = `test`.`t2`.`oref`) and trigcond(((<cache>(`test`.`t2`.`a`) = `test`.`t1`.`ie1`) or isnull(`test`.`t1`.`ie1`))) and trigcond(((<cache>(`test`.`t2`.`b`) = `test`.`t1`.`ie2`) or isnull(`test`.`t1`.`ie2`)))) having (trigcond(<is_not_null_test>(`test`.`t1`.`ie1`)) and trigcond(<is_not_null_test>(`test`.`t1`.`ie2`))))))) AS `Z` from `test`.`t2`
+Note	1003	select `test`.`t2`.`oref` AS `oref`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,<expr_cache><`test`.`t2`.`a`,`test`.`t2`.`b`,`test`.`t2`.`oref`>(<in_optimizer>((`test`.`t2`.`a`,`test`.`t2`.`b`),<exists>(<index_lookup>(<cache>(`test`.`t2`.`a`) in t1 on idx checking NULL where ((`test`.`t1`.`oref` = `test`.`t2`.`oref`) and trigcond(trigcond(((<cache>(`test`.`t2`.`a`) = `test`.`t1`.`ie1`) or isnull(`test`.`t1`.`ie1`)))) and trigcond(trigcond(((<cache>(`test`.`t2`.`b`) = `test`.`t1`.`ie2`) or isnull(`test`.`t1`.`ie2`))))) having (trigcond(<is_not_null_test>(`test`.`t1`.`ie1`)) and trigcond(<is_not_null_test>(`test`.`t1`.`ie2`))))))) AS `Z` from `test`.`t2`
 drop table t1,t2;
 create table t1 (oref char(4), grp int, ie int primary key);
 insert into t1 (oref, grp, ie) values

mysql-test/r/subselect3_jcl6.result

@@ -262,7 +262,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 2	DEPENDENT SUBQUERY	t1	index_subquery	a	a	5	func	2	100.00	Using where; Full scan on NULL key
 Warnings:
 Note	1276	Field or reference 'test.t2.oref' of SELECT #2 was resolved in SELECT #1
-Note	1003	select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t2`.`oref` AS `oref`,<expr_cache><`test`.`t2`.`a`,`test`.`t2`.`b`,`test`.`t2`.`oref`>(<in_optimizer>((`test`.`t2`.`a`,`test`.`t2`.`b`),<exists>(<index_lookup>(<cache>(`test`.`t2`.`a`) in t1 on a checking NULL where ((`test`.`t1`.`c` = `test`.`t2`.`oref`) and trigcond(((<cache>(`test`.`t2`.`a`) = `test`.`t1`.`a`) or isnull(`test`.`t1`.`a`))) and trigcond(((<cache>(`test`.`t2`.`b`) = `test`.`t1`.`b`) or isnull(`test`.`t1`.`b`)))) having (trigcond(<is_not_null_test>(`test`.`t1`.`a`)) and trigcond(<is_not_null_test>(`test`.`t1`.`b`))))))) AS `Z` from `test`.`t2`
+Note	1003	select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t2`.`oref` AS `oref`,<expr_cache><`test`.`t2`.`a`,`test`.`t2`.`b`,`test`.`t2`.`oref`>(<in_optimizer>((`test`.`t2`.`a`,`test`.`t2`.`b`),<exists>(<index_lookup>(<cache>(`test`.`t2`.`a`) in t1 on a checking NULL where ((`test`.`t1`.`c` = `test`.`t2`.`oref`) and trigcond(trigcond(((<cache>(`test`.`t2`.`a`) = `test`.`t1`.`a`) or isnull(`test`.`t1`.`a`)))) and trigcond(trigcond(((<cache>(`test`.`t2`.`b`) = `test`.`t1`.`b`) or isnull(`test`.`t1`.`b`))))) having (trigcond(<is_not_null_test>(`test`.`t1`.`a`)) and trigcond(<is_not_null_test>(`test`.`t1`.`b`))))))) AS `Z` from `test`.`t2`
 select a,b, oref, (a,b) in (select a,b from t1 where c=t2.oref) Z from t2;
 a	b	oref	Z
 NULL	1	100	0
@@ -279,7 +279,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 2	DEPENDENT SUBQUERY	t4	ALL	NULL	NULL	NULL	NULL	100	100.00	Using where; Using join buffer (flat, BNL join)
 Warnings:
 Note	1276	Field or reference 'test.t2.oref' of SELECT #2 was resolved in SELECT #1
-Note	1003	select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t2`.`oref` AS `oref`,<expr_cache><`test`.`t2`.`a`,`test`.`t2`.`b`,`test`.`t2`.`oref`>(<in_optimizer>((`test`.`t2`.`a`,`test`.`t2`.`b`),<exists>(select `test`.`t1`.`a`,`test`.`t1`.`b` from `test`.`t1` join `test`.`t4` where ((`test`.`t1`.`c` = `test`.`t2`.`oref`) and trigcond(((<cache>(`test`.`t2`.`a`) = `test`.`t1`.`a`) or isnull(`test`.`t1`.`a`))) and trigcond(((<cache>(`test`.`t2`.`b`) = `test`.`t1`.`b`) or isnull(`test`.`t1`.`b`)))) having (trigcond(<is_not_null_test>(`test`.`t1`.`a`)) and trigcond(<is_not_null_test>(`test`.`t1`.`b`)))))) AS `Z` from `test`.`t2`
+Note	1003	select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t2`.`oref` AS `oref`,<expr_cache><`test`.`t2`.`a`,`test`.`t2`.`b`,`test`.`t2`.`oref`>(<in_optimizer>((`test`.`t2`.`a`,`test`.`t2`.`b`),<exists>(select `test`.`t1`.`a`,`test`.`t1`.`b` from `test`.`t1` join `test`.`t4` where ((`test`.`t1`.`c` = `test`.`t2`.`oref`) and trigcond(trigcond(((<cache>(`test`.`t2`.`a`) = `test`.`t1`.`a`) or isnull(`test`.`t1`.`a`)))) and trigcond(trigcond(((<cache>(`test`.`t2`.`b`) = `test`.`t1`.`b`) or isnull(`test`.`t1`.`b`))))) having (trigcond(<is_not_null_test>(`test`.`t1`.`a`)) and trigcond(<is_not_null_test>(`test`.`t1`.`b`)))))) AS `Z` from `test`.`t2`
 select a,b, oref, 
 (a,b) in (select a,b from t1,t4 where c=t2.oref) Z 
 from t2;
@@ -324,7 +324,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 2	DEPENDENT SUBQUERY	t1	index_subquery	idx	idx	5	func	4	100.00	Using where; Full scan on NULL key
 Warnings:
 Note	1276	Field or reference 'test.t2.oref' of SELECT #2 was resolved in SELECT #1
-Note	1003	select `test`.`t2`.`oref` AS `oref`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,<expr_cache><`test`.`t2`.`a`,`test`.`t2`.`b`,`test`.`t2`.`oref`>(<in_optimizer>((`test`.`t2`.`a`,`test`.`t2`.`b`),<exists>(<index_lookup>(<cache>(`test`.`t2`.`a`) in t1 on idx checking NULL where ((`test`.`t1`.`oref` = `test`.`t2`.`oref`) and trigcond(((<cache>(`test`.`t2`.`a`) = `test`.`t1`.`ie1`) or isnull(`test`.`t1`.`ie1`))) and trigcond(((<cache>(`test`.`t2`.`b`) = `test`.`t1`.`ie2`) or isnull(`test`.`t1`.`ie2`)))) having (trigcond(<is_not_null_test>(`test`.`t1`.`ie1`)) and trigcond(<is_not_null_test>(`test`.`t1`.`ie2`))))))) AS `Z` from `test`.`t2` where ((`test`.`t2`.`b` = 10) and (`test`.`t2`.`a` = 10))
+Note	1003	select `test`.`t2`.`oref` AS `oref`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,<expr_cache><`test`.`t2`.`a`,`test`.`t2`.`b`,`test`.`t2`.`oref`>(<in_optimizer>((`test`.`t2`.`a`,`test`.`t2`.`b`),<exists>(<index_lookup>(<cache>(`test`.`t2`.`a`) in t1 on idx checking NULL where ((`test`.`t1`.`oref` = `test`.`t2`.`oref`) and trigcond(trigcond(((<cache>(`test`.`t2`.`a`) = `test`.`t1`.`ie1`) or isnull(`test`.`t1`.`ie1`)))) and trigcond(trigcond(((<cache>(`test`.`t2`.`b`) = `test`.`t1`.`ie2`) or isnull(`test`.`t1`.`ie2`))))) having (trigcond(<is_not_null_test>(`test`.`t1`.`ie1`)) and trigcond(<is_not_null_test>(`test`.`t1`.`ie2`))))))) AS `Z` from `test`.`t2` where ((`test`.`t2`.`b` = 10) and (`test`.`t2`.`a` = 10))
 drop table t1, t2;
 create table t1 (oref char(4), grp int, ie int);
 insert into t1 (oref, grp, ie) values
@@ -594,7 +594,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 2	DEPENDENT SUBQUERY	t1	index_subquery	idx	idx	5	func	4	100.00	Using where; Full scan on NULL key
 Warnings:
 Note	1276	Field or reference 'test.t2.oref' of SELECT #2 was resolved in SELECT #1
-Note	1003	select `test`.`t2`.`oref` AS `oref`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,<expr_cache><`test`.`t2`.`a`,`test`.`t2`.`b`,`test`.`t2`.`oref`>(<in_optimizer>((`test`.`t2`.`a`,`test`.`t2`.`b`),<exists>(<index_lookup>(<cache>(`test`.`t2`.`a`) in t1 on idx checking NULL where ((`test`.`t1`.`oref` = `test`.`t2`.`oref`) and trigcond(((<cache>(`test`.`t2`.`a`) = `test`.`t1`.`ie1`) or isnull(`test`.`t1`.`ie1`))) and trigcond(((<cache>(`test`.`t2`.`b`) = `test`.`t1`.`ie2`) or isnull(`test`.`t1`.`ie2`)))) having (trigcond(<is_not_null_test>(`test`.`t1`.`ie1`)) and trigcond(<is_not_null_test>(`test`.`t1`.`ie2`))))))) AS `Z` from `test`.`t2`
+Note	1003	select `test`.`t2`.`oref` AS `oref`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,<expr_cache><`test`.`t2`.`a`,`test`.`t2`.`b`,`test`.`t2`.`oref`>(<in_optimizer>((`test`.`t2`.`a`,`test`.`t2`.`b`),<exists>(<index_lookup>(<cache>(`test`.`t2`.`a`) in t1 on idx checking NULL where ((`test`.`t1`.`oref` = `test`.`t2`.`oref`) and trigcond(trigcond(((<cache>(`test`.`t2`.`a`) = `test`.`t1`.`ie1`) or isnull(`test`.`t1`.`ie1`)))) and trigcond(trigcond(((<cache>(`test`.`t2`.`b`) = `test`.`t1`.`ie2`) or isnull(`test`.`t1`.`ie2`))))) having (trigcond(<is_not_null_test>(`test`.`t1`.`ie1`)) and trigcond(<is_not_null_test>(`test`.`t1`.`ie2`))))))) AS `Z` from `test`.`t2`
 drop table t1,t2;
 create table t1 (oref char(4), grp int, ie int primary key);
 insert into t1 (oref, grp, ie) values

mysql-test/r/subselect4.result

@@ -303,7 +303,7 @@ EXPLAIN
 SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2a.i, t2a.pk FROM t2a WHERE t2a.pk = t1.pk);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	4	Using where
-2	DEPENDENT SUBQUERY	t2a	eq_ref	PRIMARY	PRIMARY	8	const,test.t1.pk	1	Using where; Using index; Full scan on NULL key
+2	DEPENDENT SUBQUERY	t2a	unique_subquery	PRIMARY	PRIMARY	8	const,test.t1.pk	1	Using index; Using where; Full scan on NULL key
 SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2a.i, t2a.pk FROM t2a WHERE t2a.pk = t1.pk);
 pk	i
 0	10
@@ -335,7 +335,7 @@ EXPLAIN
 SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2c.i, t2c.pk FROM t2c WHERE t2c.pk = t1.pk);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	4	Using where
-2	DEPENDENT SUBQUERY	t2c	ref	it2c	it2c	8	const,test.t1.pk	2	Using where; Using index; Full scan on NULL key
+2	DEPENDENT SUBQUERY	t2c	index_subquery	it2c	it2c	8	const,test.t1.pk	2	Using index; Using where; Full scan on NULL key
 SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2c.i, t2c.pk FROM t2c WHERE t2c.pk = t1.pk);
 pk	i
 0	10

mysql-test/r/subselect_mat_cost.result

@@ -348,7 +348,7 @@ FROM City LEFT JOIN Country ON (Country = Code and City.Population < 10000))
 AND Language IN ('English','Spanish');
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	CountryLanguage	range	Language	Language	30	NULL	72	Using index condition; Using where; Rowid-ordered scan
-2	DEPENDENT SUBQUERY	City	ref	CityName	CityName	35	func	1	Using index condition; Using where
+2	DEPENDENT SUBQUERY	City	ref	CityName	CityName	35	func	1	Using index condition
 2	DEPENDENT SUBQUERY	Country	eq_ref	PRIMARY	PRIMARY	3	world.City.Country	1	Using where; Using index
 select count(*)
 from CountryLanguage

mysql-test/r/subselect_no_mat.result

@@ -2973,7 +2973,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	100.00	
 2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	9	100.00	Using where
 Warnings:
-Note	1003	select `test`.`t1`.`one` AS `one`,`test`.`t1`.`two` AS `two`,<expr_cache><`test`.`t1`.`one`,`test`.`t1`.`two`>(<in_optimizer>((`test`.`t1`.`one`,`test`.`t1`.`two`),<exists>(select `test`.`t2`.`one`,`test`.`t2`.`two` from `test`.`t2` where ((`test`.`t2`.`flag` = '0') and trigcond(((<cache>(`test`.`t1`.`one`) = `test`.`t2`.`one`) or isnull(`test`.`t2`.`one`))) and trigcond(((<cache>(`test`.`t1`.`two`) = `test`.`t2`.`two`) or isnull(`test`.`t2`.`two`)))) having (trigcond(<is_not_null_test>(`test`.`t2`.`one`)) and trigcond(<is_not_null_test>(`test`.`t2`.`two`)))))) AS `test` from `test`.`t1`
+Note	1003	select `test`.`t1`.`one` AS `one`,`test`.`t1`.`two` AS `two`,<expr_cache><`test`.`t1`.`one`,`test`.`t1`.`two`>(<in_optimizer>((`test`.`t1`.`one`,`test`.`t1`.`two`),<exists>(select `test`.`t2`.`one`,`test`.`t2`.`two` from `test`.`t2` where ((`test`.`t2`.`flag` = '0') and trigcond(trigcond(((<cache>(`test`.`t1`.`one`) = `test`.`t2`.`one`) or isnull(`test`.`t2`.`one`)))) and trigcond(trigcond(((<cache>(`test`.`t1`.`two`) = `test`.`t2`.`two`) or isnull(`test`.`t2`.`two`))))) having (trigcond(<is_not_null_test>(`test`.`t2`.`one`)) and trigcond(<is_not_null_test>(`test`.`t2`.`two`)))))) AS `test` from `test`.`t1`
 explain extended SELECT one,two from t1 where ROW(one,two) IN (SELECT one,two FROM t2 WHERE flag = 'N');
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	100.00	
@@ -2985,7 +2985,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	100.00	
 2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	9	100.00	Using where
 Warnings:
-Note	1003	select `test`.`t1`.`one` AS `one`,`test`.`t1`.`two` AS `two`,<expr_cache><`test`.`t1`.`one`,`test`.`t1`.`two`>(<in_optimizer>((`test`.`t1`.`one`,`test`.`t1`.`two`),<exists>(select `test`.`t2`.`one`,`test`.`t2`.`two` from `test`.`t2` where ((`test`.`t2`.`flag` = '0') and trigcond(((<cache>(`test`.`t1`.`one`) = `test`.`t2`.`one`) or isnull(`test`.`t2`.`one`))) and trigcond(((<cache>(`test`.`t1`.`two`) = `test`.`t2`.`two`) or isnull(`test`.`t2`.`two`)))) having (trigcond(<is_not_null_test>(`test`.`t2`.`one`)) and trigcond(<is_not_null_test>(`test`.`t2`.`two`)))))) AS `test` from `test`.`t1`
+Note	1003	select `test`.`t1`.`one` AS `one`,`test`.`t1`.`two` AS `two`,<expr_cache><`test`.`t1`.`one`,`test`.`t1`.`two`>(<in_optimizer>((`test`.`t1`.`one`,`test`.`t1`.`two`),<exists>(select `test`.`t2`.`one`,`test`.`t2`.`two` from `test`.`t2` where ((`test`.`t2`.`flag` = '0') and trigcond(trigcond(((<cache>(`test`.`t1`.`one`) = `test`.`t2`.`one`) or isnull(`test`.`t2`.`one`)))) and trigcond(trigcond(((<cache>(`test`.`t1`.`two`) = `test`.`t2`.`two`) or isnull(`test`.`t2`.`two`))))) having (trigcond(<is_not_null_test>(`test`.`t2`.`one`)) and trigcond(<is_not_null_test>(`test`.`t2`.`two`)))))) AS `test` from `test`.`t1`
 DROP TABLE t1,t2;
 set optimizer_switch=@tmp11867_optimizer_switch;
 CREATE TABLE t1 (a char(5), b char(5));

mysql-test/r/subselect_no_opts.result

@@ -2969,7 +2969,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	100.00	
 2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	9	100.00	Using where
 Warnings:
-Note	1003	select `test`.`t1`.`one` AS `one`,`test`.`t1`.`two` AS `two`,<in_optimizer>((`test`.`t1`.`one`,`test`.`t1`.`two`),<exists>(select `test`.`t2`.`one`,`test`.`t2`.`two` from `test`.`t2` where ((`test`.`t2`.`flag` = '0') and trigcond(((<cache>(`test`.`t1`.`one`) = `test`.`t2`.`one`) or isnull(`test`.`t2`.`one`))) and trigcond(((<cache>(`test`.`t1`.`two`) = `test`.`t2`.`two`) or isnull(`test`.`t2`.`two`)))) having (trigcond(<is_not_null_test>(`test`.`t2`.`one`)) and trigcond(<is_not_null_test>(`test`.`t2`.`two`))))) AS `test` from `test`.`t1`
+Note	1003	select `test`.`t1`.`one` AS `one`,`test`.`t1`.`two` AS `two`,<in_optimizer>((`test`.`t1`.`one`,`test`.`t1`.`two`),<exists>(select `test`.`t2`.`one`,`test`.`t2`.`two` from `test`.`t2` where ((`test`.`t2`.`flag` = '0') and trigcond(trigcond(((<cache>(`test`.`t1`.`one`) = `test`.`t2`.`one`) or isnull(`test`.`t2`.`one`)))) and trigcond(trigcond(((<cache>(`test`.`t1`.`two`) = `test`.`t2`.`two`) or isnull(`test`.`t2`.`two`))))) having (trigcond(<is_not_null_test>(`test`.`t2`.`one`)) and trigcond(<is_not_null_test>(`test`.`t2`.`two`))))) AS `test` from `test`.`t1`
 explain extended SELECT one,two from t1 where ROW(one,two) IN (SELECT one,two FROM t2 WHERE flag = 'N');
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	100.00	Using where
@@ -2981,7 +2981,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	100.00	
 2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	9	100.00	Using where
 Warnings:
-Note	1003	select `test`.`t1`.`one` AS `one`,`test`.`t1`.`two` AS `two`,<in_optimizer>((`test`.`t1`.`one`,`test`.`t1`.`two`),<exists>(select `test`.`t2`.`one`,`test`.`t2`.`two` from `test`.`t2` where ((`test`.`t2`.`flag` = '0') and trigcond(((<cache>(`test`.`t1`.`one`) = `test`.`t2`.`one`) or isnull(`test`.`t2`.`one`))) and trigcond(((<cache>(`test`.`t1`.`two`) = `test`.`t2`.`two`) or isnull(`test`.`t2`.`two`)))) having (trigcond(<is_not_null_test>(`test`.`t2`.`one`)) and trigcond(<is_not_null_test>(`test`.`t2`.`two`))))) AS `test` from `test`.`t1`
+Note	1003	select `test`.`t1`.`one` AS `one`,`test`.`t1`.`two` AS `two`,<in_optimizer>((`test`.`t1`.`one`,`test`.`t1`.`two`),<exists>(select `test`.`t2`.`one`,`test`.`t2`.`two` from `test`.`t2` where ((`test`.`t2`.`flag` = '0') and trigcond(trigcond(((<cache>(`test`.`t1`.`one`) = `test`.`t2`.`one`) or isnull(`test`.`t2`.`one`)))) and trigcond(trigcond(((<cache>(`test`.`t1`.`two`) = `test`.`t2`.`two`) or isnull(`test`.`t2`.`two`))))) having (trigcond(<is_not_null_test>(`test`.`t2`.`one`)) and trigcond(<is_not_null_test>(`test`.`t2`.`two`))))) AS `test` from `test`.`t1`
 DROP TABLE t1,t2;
 set optimizer_switch=@tmp11867_optimizer_switch;
 CREATE TABLE t1 (a char(5), b char(5));

mysql-test/r/subselect_no_scache.result

@@ -2972,7 +2972,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	100.00	
 2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	9	100.00	Using where
 Warnings:
-Note	1003	select `test`.`t1`.`one` AS `one`,`test`.`t1`.`two` AS `two`,<in_optimizer>((`test`.`t1`.`one`,`test`.`t1`.`two`),<exists>(select `test`.`t2`.`one`,`test`.`t2`.`two` from `test`.`t2` where ((`test`.`t2`.`flag` = '0') and trigcond(((<cache>(`test`.`t1`.`one`) = `test`.`t2`.`one`) or isnull(`test`.`t2`.`one`))) and trigcond(((<cache>(`test`.`t1`.`two`) = `test`.`t2`.`two`) or isnull(`test`.`t2`.`two`)))) having (trigcond(<is_not_null_test>(`test`.`t2`.`one`)) and trigcond(<is_not_null_test>(`test`.`t2`.`two`))))) AS `test` from `test`.`t1`
+Note	1003	select `test`.`t1`.`one` AS `one`,`test`.`t1`.`two` AS `two`,<in_optimizer>((`test`.`t1`.`one`,`test`.`t1`.`two`),<exists>(select `test`.`t2`.`one`,`test`.`t2`.`two` from `test`.`t2` where ((`test`.`t2`.`flag` = '0') and trigcond(trigcond(((<cache>(`test`.`t1`.`one`) = `test`.`t2`.`one`) or isnull(`test`.`t2`.`one`)))) and trigcond(trigcond(((<cache>(`test`.`t1`.`two`) = `test`.`t2`.`two`) or isnull(`test`.`t2`.`two`))))) having (trigcond(<is_not_null_test>(`test`.`t2`.`one`)) and trigcond(<is_not_null_test>(`test`.`t2`.`two`))))) AS `test` from `test`.`t1`
 explain extended SELECT one,two from t1 where ROW(one,two) IN (SELECT one,two FROM t2 WHERE flag = 'N');
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	100.00	
@@ -2985,7 +2985,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	8	100.00	
 2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	9	100.00	Using where
 Warnings:
-Note	1003	select `test`.`t1`.`one` AS `one`,`test`.`t1`.`two` AS `two`,<in_optimizer>((`test`.`t1`.`one`,`test`.`t1`.`two`),<exists>(select `test`.`t2`.`one`,`test`.`t2`.`two` from `test`.`t2` where ((`test`.`t2`.`flag` = '0') and trigcond(((<cache>(`test`.`t1`.`one`) = `test`.`t2`.`one`) or isnull(`test`.`t2`.`one`))) and trigcond(((<cache>(`test`.`t1`.`two`) = `test`.`t2`.`two`) or isnull(`test`.`t2`.`two`)))) having (trigcond(<is_not_null_test>(`test`.`t2`.`one`)) and trigcond(<is_not_null_test>(`test`.`t2`.`two`))))) AS `test` from `test`.`t1`
+Note	1003	select `test`.`t1`.`one` AS `one`,`test`.`t1`.`two` AS `two`,<in_optimizer>((`test`.`t1`.`one`,`test`.`t1`.`two`),<exists>(select `test`.`t2`.`one`,`test`.`t2`.`two` from `test`.`t2` where ((`test`.`t2`.`flag` = '0') and trigcond(trigcond(((<cache>(`test`.`t1`.`one`) = `test`.`t2`.`one`) or isnull(`test`.`t2`.`one`)))) and trigcond(trigcond(((<cache>(`test`.`t1`.`two`) = `test`.`t2`.`two`) or isnull(`test`.`t2`.`two`))))) having (trigcond(<is_not_null_test>(`test`.`t2`.`one`)) and trigcond(<is_not_null_test>(`test`.`t2`.`two`))))) AS `test` from `test`.`t1`
 DROP TABLE t1,t2;
 set optimizer_switch=@tmp11867_optimizer_switch;
 CREATE TABLE t1 (a char(5), b char(5));

sql/item_subselect.cc

@@ -2306,7 +2306,7 @@ Item_in_subselect::create_row_in_to_exists_cond(JOIN * join,
                                          ref_pointer_array+i,
                                          (char *)"<no matter>",
                                          (char *)"<list ref>"));
-      if (!abort_on_null)
+      if (!abort_on_null && select_lex->ref_pointer_array[i]->maybe_null)
       {
         Item *having_col_item=
           new Item_is_not_null_test(this,
@@ -2325,10 +2325,6 @@ Item_in_subselect::create_row_in_to_exists_cond(JOIN * join,
                                            (char *)"<no matter>",
                                            (char *)"<list ref>"));
         item= new Item_cond_or(item, item_isnull);
-        /* 
-          TODO: why we create the above for cases where the right part
-                cant be NULL?
-        */
         if (left_expr->element_index(i)->maybe_null)
         {
           if (!(item= new Item_func_trig_cond(item, get_cond_guard(i))))
@@ -2339,6 +2335,11 @@ Item_in_subselect::create_row_in_to_exists_cond(JOIN * join,
         }
         *having_item= and_items(*having_item, having_col_item);
       }
+      if (!abort_on_null && left_expr->element_index(i)->maybe_null)
+      {
+        if (!(item= new Item_func_trig_cond(item, get_cond_guard(i))))
+          DBUG_RETURN(true);
+      }
       *where_item= and_items(*where_item, item);
     }
   }