Bug#21574933 Extra rows with derived table in subquery + XOR

This problem stems from the transformation of IN subqueries
in Item_in_subselect::single_value_in_to_exists_transformer().

The source of the regression is the fix for bug no. 14358878, which
wrapped all selected columns from a derived table that was on the
inner side of an outer join in Item_direct_view_ref objects.
The purpose of the wrapping was to make the columns nullable and
nullability depending on some table from the derived table.

single_value_in_to_exists_transformer() calculated orig_item from one
such column. Prior to the wrapping, nullability information was present
in orig_item. But after the bugfix, real_item() would pass the
Item_direct_view_ref object and return the underlying Item object,
which is not necessarily nullable.

real_item() was originally used so that we do not build a permanent
subquery transformation on top of a runtime item. The wrapped
Item_direct_view_ref objects are runtime objects, meaning that
they cannot be used in a permanent transformation.
The solution is a kludge: If the Item_direct_view_ref object is
nullable, we set the item being pointed to from the
Item_direct_view_ref as nullable as well. This means that we pick up
correct nullability, but the item does not correctly reflect the
nullability of the datum. However, we have not been able to identify
a situation where this causes erroneous or non-optimal execution.

Further on, this means that NULL values from outer joined tables
are included in the query result, meaning that the IN subquery
can return NULL instead of FALSE in cases like this.

Author: roylyseng

mysql-test/include/subquery.inc

@@ -6528,3 +6528,58 @@ SELECT
 FROM t1 AS x3;
 
 DROP TABLE t1,t2;
+
+--echo # Bug#21574933 Extra rows with derived table in subquery + XOR
+
+CREATE TABLE t1 (
+  pk INT NOT NULL,
+  col_date DATE,
+  PRIMARY KEY (pk)
+);
+
+INSERT INTO t1 VALUES (1,'2008-06-18'), (4,NULL);
+
+CREATE TABLE t2 (
+  col_date DATE,
+  pk INT NOT NULL,
+  PRIMARY KEY (pk)
+);
+
+INSERT INTO t2 VALUES ('2002-02-02',1);
+
+CREATE TABLE t3 (
+  pk INT NOT NULL,
+  col_varchar VARCHAR(1),
+  col_int_key INT,
+  col_int INT,
+  PRIMARY KEY (pk),
+  KEY col_int_key (col_int_key)
+);
+
+INSERT INTO t3 VALUES (4,'l',2,2);
+
+let $query=
+SELECT pk,
+       col_int IN
+       (SELECT innr1.pk
+        FROM t1 AS innr2
+             LEFT JOIN (SELECT pk, col_date FROM t2) AS innr1
+             ON innr2.col_date <> innr1.col_date
+        WHERE outr.col_int_key < 6) AS x
+FROM t3 AS outr;
+
+eval explain $query;
+eval $query;
+
+let $query=
+SELECT pk,
+       col_int IN
+       (SELECT innr1.pk
+        FROM t1 AS innr2
+             LEFT JOIN (SELECT pk, date'2015-01-01' AS d FROM t2) AS innr1
+             ON innr2.col_date <> innr1.d
+        WHERE outr.col_int_key < 6) AS x
+FROM t3 AS outr;
+eval $query;
+
+DROP TABLE t1, t2, t3;

mysql-test/r/subquery_all.result

@@ -8009,4 +8009,62 @@ FROM t1 AS x3;
 result
 0
 DROP TABLE t1,t2;
+# Bug#21574933 Extra rows with derived table in subquery + XOR
+CREATE TABLE t1 (
+pk INT NOT NULL,
+col_date DATE,
+PRIMARY KEY (pk)
+);
+INSERT INTO t1 VALUES (1,'2008-06-18'), (4,NULL);
+CREATE TABLE t2 (
+col_date DATE,
+pk INT NOT NULL,
+PRIMARY KEY (pk)
+);
+INSERT INTO t2 VALUES ('2002-02-02',1);
+CREATE TABLE t3 (
+pk INT NOT NULL,
+col_varchar VARCHAR(1),
+col_int_key INT,
+col_int INT,
+PRIMARY KEY (pk),
+KEY col_int_key (col_int_key)
+);
+INSERT INTO t3 VALUES (4,'l',2,2);
+explain SELECT pk,
+col_int IN
+(SELECT innr1.pk
+FROM t1 AS innr2
+LEFT JOIN (SELECT pk, col_date FROM t2) AS innr1
+ON innr2.col_date <> innr1.col_date
+WHERE outr.col_int_key < 6) AS x
+FROM t3 AS outr;
+id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	PRIMARY	outr	NULL	ALL	NULL	NULL	NULL	NULL	1	100.00	NULL
+2	DEPENDENT SUBQUERY	innr2	NULL	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+2	DEPENDENT SUBQUERY	t2	NULL	ALL	NULL	NULL	NULL	NULL	1	100.00	Using where; Using join buffer (Block Nested Loop)
+Warnings:
+Note	1276	Field or reference 'test.outr.col_int_key' of SELECT #2 was resolved in SELECT #1
+Note	1003	/* select#1 */ select `test`.`outr`.`pk` AS `pk`,<in_optimizer>(`test`.`outr`.`col_int`,<exists>(/* select#2 */ select 1 from `test`.`t1` `innr2` left join (`test`.`t2`) on((`test`.`innr2`.`col_date` <> `test`.`t2`.`col_date`)) where ((`test`.`outr`.`col_int_key` < 6) and <if>(outer_field_is_not_null, ((<cache>(`test`.`outr`.`col_int`) = `test`.`t2`.`pk`) or isnull(`test`.`t2`.`pk`)), true)) having <if>(outer_field_is_not_null, <is_not_null_test>(`test`.`t2`.`pk`), true))) AS `x` from `test`.`t3` `outr`
+SELECT pk,
+col_int IN
+(SELECT innr1.pk
+FROM t1 AS innr2
+LEFT JOIN (SELECT pk, col_date FROM t2) AS innr1
+ON innr2.col_date <> innr1.col_date
+WHERE outr.col_int_key < 6) AS x
+FROM t3 AS outr;
+pk	x
+4	NULL
+SELECT pk,
+col_int IN
+(SELECT innr1.pk
+FROM t1 AS innr2
+LEFT JOIN (SELECT pk, date'2015-01-01' AS d FROM t2) AS innr1
+ON innr2.col_date <> innr1.d
+WHERE outr.col_int_key < 6) AS x
+FROM t3 AS outr;
+pk	x
+4	NULL
+DROP TABLE t1, t2, t3;
 set optimizer_switch=default;

mysql-test/r/subquery_all_bka.result

@@ -8010,5 +8010,63 @@ FROM t1 AS x3;
 result
 0
 DROP TABLE t1,t2;
+# Bug#21574933 Extra rows with derived table in subquery + XOR
+CREATE TABLE t1 (
+pk INT NOT NULL,
+col_date DATE,
+PRIMARY KEY (pk)
+);
+INSERT INTO t1 VALUES (1,'2008-06-18'), (4,NULL);
+CREATE TABLE t2 (
+col_date DATE,
+pk INT NOT NULL,
+PRIMARY KEY (pk)
+);
+INSERT INTO t2 VALUES ('2002-02-02',1);
+CREATE TABLE t3 (
+pk INT NOT NULL,
+col_varchar VARCHAR(1),
+col_int_key INT,
+col_int INT,
+PRIMARY KEY (pk),
+KEY col_int_key (col_int_key)
+);
+INSERT INTO t3 VALUES (4,'l',2,2);
+explain SELECT pk,
+col_int IN
+(SELECT innr1.pk
+FROM t1 AS innr2
+LEFT JOIN (SELECT pk, col_date FROM t2) AS innr1
+ON innr2.col_date <> innr1.col_date
+WHERE outr.col_int_key < 6) AS x
+FROM t3 AS outr;
+id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	PRIMARY	outr	NULL	ALL	NULL	NULL	NULL	NULL	1	100.00	NULL
+2	DEPENDENT SUBQUERY	innr2	NULL	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+2	DEPENDENT SUBQUERY	t2	NULL	ALL	NULL	NULL	NULL	NULL	1	100.00	Using where; Using join buffer (Block Nested Loop)
+Warnings:
+Note	1276	Field or reference 'test.outr.col_int_key' of SELECT #2 was resolved in SELECT #1
+Note	1003	/* select#1 */ select `test`.`outr`.`pk` AS `pk`,<in_optimizer>(`test`.`outr`.`col_int`,<exists>(/* select#2 */ select 1 from `test`.`t1` `innr2` left join (`test`.`t2`) on((`test`.`innr2`.`col_date` <> `test`.`t2`.`col_date`)) where ((`test`.`outr`.`col_int_key` < 6) and <if>(outer_field_is_not_null, ((<cache>(`test`.`outr`.`col_int`) = `test`.`t2`.`pk`) or isnull(`test`.`t2`.`pk`)), true)) having <if>(outer_field_is_not_null, <is_not_null_test>(`test`.`t2`.`pk`), true))) AS `x` from `test`.`t3` `outr`
+SELECT pk,
+col_int IN
+(SELECT innr1.pk
+FROM t1 AS innr2
+LEFT JOIN (SELECT pk, col_date FROM t2) AS innr1
+ON innr2.col_date <> innr1.col_date
+WHERE outr.col_int_key < 6) AS x
+FROM t3 AS outr;
+pk	x
+4	NULL
+SELECT pk,
+col_int IN
+(SELECT innr1.pk
+FROM t1 AS innr2
+LEFT JOIN (SELECT pk, date'2015-01-01' AS d FROM t2) AS innr1
+ON innr2.col_date <> innr1.d
+WHERE outr.col_int_key < 6) AS x
+FROM t3 AS outr;
+pk	x
+4	NULL
+DROP TABLE t1, t2, t3;
 set optimizer_switch=default;
 set optimizer_switch=default;

mysql-test/r/subquery_all_bka_nixbnl.result

@@ -8010,5 +8010,63 @@ FROM t1 AS x3;
 result
 0
 DROP TABLE t1,t2;
+# Bug#21574933 Extra rows with derived table in subquery + XOR
+CREATE TABLE t1 (
+pk INT NOT NULL,
+col_date DATE,
+PRIMARY KEY (pk)
+);
+INSERT INTO t1 VALUES (1,'2008-06-18'), (4,NULL);
+CREATE TABLE t2 (
+col_date DATE,
+pk INT NOT NULL,
+PRIMARY KEY (pk)
+);
+INSERT INTO t2 VALUES ('2002-02-02',1);
+CREATE TABLE t3 (
+pk INT NOT NULL,
+col_varchar VARCHAR(1),
+col_int_key INT,
+col_int INT,
+PRIMARY KEY (pk),
+KEY col_int_key (col_int_key)
+);
+INSERT INTO t3 VALUES (4,'l',2,2);
+explain SELECT pk,
+col_int IN
+(SELECT innr1.pk
+FROM t1 AS innr2
+LEFT JOIN (SELECT pk, col_date FROM t2) AS innr1
+ON innr2.col_date <> innr1.col_date
+WHERE outr.col_int_key < 6) AS x
+FROM t3 AS outr;
+id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	PRIMARY	outr	NULL	ALL	NULL	NULL	NULL	NULL	1	100.00	NULL
+2	DEPENDENT SUBQUERY	innr2	NULL	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+2	DEPENDENT SUBQUERY	t2	NULL	ALL	NULL	NULL	NULL	NULL	1	100.00	Using where
+Warnings:
+Note	1276	Field or reference 'test.outr.col_int_key' of SELECT #2 was resolved in SELECT #1
+Note	1003	/* select#1 */ select `test`.`outr`.`pk` AS `pk`,<in_optimizer>(`test`.`outr`.`col_int`,<exists>(/* select#2 */ select 1 from `test`.`t1` `innr2` left join (`test`.`t2`) on((`test`.`innr2`.`col_date` <> `test`.`t2`.`col_date`)) where ((`test`.`outr`.`col_int_key` < 6) and <if>(outer_field_is_not_null, ((<cache>(`test`.`outr`.`col_int`) = `test`.`t2`.`pk`) or isnull(`test`.`t2`.`pk`)), true)) having <if>(outer_field_is_not_null, <is_not_null_test>(`test`.`t2`.`pk`), true))) AS `x` from `test`.`t3` `outr`
+SELECT pk,
+col_int IN
+(SELECT innr1.pk
+FROM t1 AS innr2
+LEFT JOIN (SELECT pk, col_date FROM t2) AS innr1
+ON innr2.col_date <> innr1.col_date
+WHERE outr.col_int_key < 6) AS x
+FROM t3 AS outr;
+pk	x
+4	NULL
+SELECT pk,
+col_int IN
+(SELECT innr1.pk
+FROM t1 AS innr2
+LEFT JOIN (SELECT pk, date'2015-01-01' AS d FROM t2) AS innr1
+ON innr2.col_date <> innr1.d
+WHERE outr.col_int_key < 6) AS x
+FROM t3 AS outr;
+pk	x
+4	NULL
+DROP TABLE t1, t2, t3;
 set optimizer_switch=default;
 set optimizer_switch=default;

mysql-test/r/subquery_nomat_nosj.result

@@ -8009,4 +8009,62 @@ FROM t1 AS x3;
 result
 0
 DROP TABLE t1,t2;
+# Bug#21574933 Extra rows with derived table in subquery + XOR
+CREATE TABLE t1 (
+pk INT NOT NULL,
+col_date DATE,
+PRIMARY KEY (pk)
+);
+INSERT INTO t1 VALUES (1,'2008-06-18'), (4,NULL);
+CREATE TABLE t2 (
+col_date DATE,
+pk INT NOT NULL,
+PRIMARY KEY (pk)
+);
+INSERT INTO t2 VALUES ('2002-02-02',1);
+CREATE TABLE t3 (
+pk INT NOT NULL,
+col_varchar VARCHAR(1),
+col_int_key INT,
+col_int INT,
+PRIMARY KEY (pk),
+KEY col_int_key (col_int_key)
+);
+INSERT INTO t3 VALUES (4,'l',2,2);
+explain SELECT pk,
+col_int IN
+(SELECT innr1.pk
+FROM t1 AS innr2
+LEFT JOIN (SELECT pk, col_date FROM t2) AS innr1
+ON innr2.col_date <> innr1.col_date
+WHERE outr.col_int_key < 6) AS x
+FROM t3 AS outr;
+id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	PRIMARY	outr	NULL	ALL	NULL	NULL	NULL	NULL	1	100.00	NULL
+2	DEPENDENT SUBQUERY	innr2	NULL	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+2	DEPENDENT SUBQUERY	t2	NULL	ALL	NULL	NULL	NULL	NULL	1	100.00	Using where; Using join buffer (Block Nested Loop)
+Warnings:
+Note	1276	Field or reference 'test.outr.col_int_key' of SELECT #2 was resolved in SELECT #1
+Note	1003	/* select#1 */ select `test`.`outr`.`pk` AS `pk`,<in_optimizer>(`test`.`outr`.`col_int`,<exists>(/* select#2 */ select 1 from `test`.`t1` `innr2` left join (`test`.`t2`) on((`test`.`innr2`.`col_date` <> `test`.`t2`.`col_date`)) where ((`test`.`outr`.`col_int_key` < 6) and <if>(outer_field_is_not_null, ((<cache>(`test`.`outr`.`col_int`) = `test`.`t2`.`pk`) or isnull(`test`.`t2`.`pk`)), true)) having <if>(outer_field_is_not_null, <is_not_null_test>(`test`.`t2`.`pk`), true))) AS `x` from `test`.`t3` `outr`
+SELECT pk,
+col_int IN
+(SELECT innr1.pk
+FROM t1 AS innr2
+LEFT JOIN (SELECT pk, col_date FROM t2) AS innr1
+ON innr2.col_date <> innr1.col_date
+WHERE outr.col_int_key < 6) AS x
+FROM t3 AS outr;
+pk	x
+4	NULL
+SELECT pk,
+col_int IN
+(SELECT innr1.pk
+FROM t1 AS innr2
+LEFT JOIN (SELECT pk, date'2015-01-01' AS d FROM t2) AS innr1
+ON innr2.col_date <> innr1.d
+WHERE outr.col_int_key < 6) AS x
+FROM t3 AS outr;
+pk	x
+4	NULL
+DROP TABLE t1, t2, t3;
 set optimizer_switch=default;

mysql-test/r/subquery_nomat_nosj_bka.result

@@ -8010,5 +8010,63 @@ FROM t1 AS x3;
 result
 0
 DROP TABLE t1,t2;
+# Bug#21574933 Extra rows with derived table in subquery + XOR
+CREATE TABLE t1 (
+pk INT NOT NULL,
+col_date DATE,
+PRIMARY KEY (pk)
+);
+INSERT INTO t1 VALUES (1,'2008-06-18'), (4,NULL);
+CREATE TABLE t2 (
+col_date DATE,
+pk INT NOT NULL,
+PRIMARY KEY (pk)
+);
+INSERT INTO t2 VALUES ('2002-02-02',1);
+CREATE TABLE t3 (
+pk INT NOT NULL,
+col_varchar VARCHAR(1),
+col_int_key INT,
+col_int INT,
+PRIMARY KEY (pk),
+KEY col_int_key (col_int_key)
+);
+INSERT INTO t3 VALUES (4,'l',2,2);
+explain SELECT pk,
+col_int IN
+(SELECT innr1.pk
+FROM t1 AS innr2
+LEFT JOIN (SELECT pk, col_date FROM t2) AS innr1
+ON innr2.col_date <> innr1.col_date
+WHERE outr.col_int_key < 6) AS x
+FROM t3 AS outr;
+id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	PRIMARY	outr	NULL	ALL	NULL	NULL	NULL	NULL	1	100.00	NULL
+2	DEPENDENT SUBQUERY	innr2	NULL	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+2	DEPENDENT SUBQUERY	t2	NULL	ALL	NULL	NULL	NULL	NULL	1	100.00	Using where; Using join buffer (Block Nested Loop)
+Warnings:
+Note	1276	Field or reference 'test.outr.col_int_key' of SELECT #2 was resolved in SELECT #1
+Note	1003	/* select#1 */ select `test`.`outr`.`pk` AS `pk`,<in_optimizer>(`test`.`outr`.`col_int`,<exists>(/* select#2 */ select 1 from `test`.`t1` `innr2` left join (`test`.`t2`) on((`test`.`innr2`.`col_date` <> `test`.`t2`.`col_date`)) where ((`test`.`outr`.`col_int_key` < 6) and <if>(outer_field_is_not_null, ((<cache>(`test`.`outr`.`col_int`) = `test`.`t2`.`pk`) or isnull(`test`.`t2`.`pk`)), true)) having <if>(outer_field_is_not_null, <is_not_null_test>(`test`.`t2`.`pk`), true))) AS `x` from `test`.`t3` `outr`
+SELECT pk,
+col_int IN
+(SELECT innr1.pk
+FROM t1 AS innr2
+LEFT JOIN (SELECT pk, col_date FROM t2) AS innr1
+ON innr2.col_date <> innr1.col_date
+WHERE outr.col_int_key < 6) AS x
+FROM t3 AS outr;
+pk	x
+4	NULL
+SELECT pk,
+col_int IN
+(SELECT innr1.pk
+FROM t1 AS innr2
+LEFT JOIN (SELECT pk, date'2015-01-01' AS d FROM t2) AS innr1
+ON innr2.col_date <> innr1.d
+WHERE outr.col_int_key < 6) AS x
+FROM t3 AS outr;
+pk	x
+4	NULL
+DROP TABLE t1, t2, t3;
 set optimizer_switch=default;
 set optimizer_switch=default;