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.

1 files changed, 4 insertions, 4 deletions

diff --git a/mysql-test/r/subselect3.result b/mysql-test/r/subselect3.result
index 049c4d14b1a..ed07578fa17 100644
--- a/mysql-test/r/subselect3.result
+++ b/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