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MDEV-9513: Assertion `join->group_list || !join->is_in_subquery()' failed in create_sort_index

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Removing the ORDER BY clause from the UNION when UNION is inside an IN/ALL/ANY/EXISTS subquery.
The rewrites are done for subqueries but this rewrite is not done for the fake_select of
the UNION.
This commit is contained in:
Varun Gupta
2020-08-04 14:36:01 +05:30
parent 0e80f5a693
commit ab578bdf45
4 changed files with 89 additions and 0 deletions
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41
mysql-test/r/subselect4.result
View File

@ -2608,3 +2608,44 @@ region area population
Central America and the Caribbean 442 66422
SET @@optimizer_switch= @save_optimizer_switch;
DROP TABLE t1;
#
# MDEV-9513: Assertion `join->group_list || !join->is_in_subquery()' failed in create_sort_index
#
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (1),(2);
CREATE TABLE t2 (a INT);
INSERT INTO t2 VALUES (2),(3);
EXPLAIN
SELECT t1.a FROM t1 WHERE t1.a IN ( SELECT A.a FROM t1 A UNION SELECT B.a FROM t2 B ORDER BY 1);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2 Using where
2 DEPENDENT SUBQUERY A ALL NULL NULL NULL NULL 2 Using where
3 DEPENDENT UNION B ALL NULL NULL NULL NULL 2 Using where
NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL
SELECT t1.a FROM t1 WHERE t1.a IN ( SELECT A.a FROM t1 A UNION SELECT B.a FROM t2 B ORDER BY 1);
a
1
2
EXPLAIN
SELECT t1.a FROM t1 WHERE EXISTS (SELECT A.a FROM t1 A UNION SELECT B.a FROM t2 B ORDER BY 1);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2
2 SUBQUERY A ALL NULL NULL NULL NULL 2
3 UNION B ALL NULL NULL NULL NULL 2
NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL
SELECT t1.a FROM t1 WHERE EXISTS (SELECT A.a FROM t1 A UNION SELECT B.a FROM t2 B ORDER BY 1);
a
1
2
EXPLAIN
SELECT t1.a FROM t1 WHERE t1.a IN ( SELECT A.a FROM t1 A UNION ALL SELECT B.a FROM t2 B ORDER BY 1);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2 Using where
2 DEPENDENT SUBQUERY A ALL NULL NULL NULL NULL 2 Using where
3 DEPENDENT UNION B ALL NULL NULL NULL NULL 2 Using where
SELECT t1.a FROM t1 WHERE t1.a IN ( SELECT A.a FROM t1 A UNION ALL SELECT B.a FROM t2 B ORDER BY 1);
a
1
2
DROP TABLE t1,t2;
# end of 10.1 tests

25
mysql-test/t/subselect4.test
View File

@ -2138,3 +2138,28 @@ WHERE population/area = (SELECT MAX(population/area) from t1 B where A.region =
SET @@optimizer_switch= @save_optimizer_switch;
DROP TABLE t1;
--echo #
--echo # MDEV-9513: Assertion `join->group_list || !join->is_in_subquery()' failed in create_sort_index
--echo #
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (1),(2);
CREATE TABLE t2 (a INT);
INSERT INTO t2 VALUES (2),(3);
EXPLAIN
SELECT t1.a FROM t1 WHERE t1.a IN ( SELECT A.a FROM t1 A UNION SELECT B.a FROM t2 B ORDER BY 1);
SELECT t1.a FROM t1 WHERE t1.a IN ( SELECT A.a FROM t1 A UNION SELECT B.a FROM t2 B ORDER BY 1);
EXPLAIN
SELECT t1.a FROM t1 WHERE EXISTS (SELECT A.a FROM t1 A UNION SELECT B.a FROM t2 B ORDER BY 1);
SELECT t1.a FROM t1 WHERE EXISTS (SELECT A.a FROM t1 A UNION SELECT B.a FROM t2 B ORDER BY 1);
EXPLAIN
SELECT t1.a FROM t1 WHERE t1.a IN ( SELECT A.a FROM t1 A UNION ALL SELECT B.a FROM t2 B ORDER BY 1);
SELECT t1.a FROM t1 WHERE t1.a IN ( SELECT A.a FROM t1 A UNION ALL SELECT B.a FROM t2 B ORDER BY 1);
DROP TABLE t1,t2;
--echo # end of 10.1 tests

4
sql/item_subselect.h
View File

@ -131,6 +131,10 @@ public:
Item_subselect(THD *thd);
virtual subs_type substype() { return UNKNOWN_SUBS; }
bool is_exists_predicate()
{
return substype() == Item_subselect::EXISTS_SUBS;
}
bool is_in_predicate()
{
return (substype() == Item_subselect::IN_SUBS ||

19
sql/sql_union.cc
View File

@ -388,6 +388,25 @@ bool st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
found_rows_for_union= first_sl->options & OPTION_FOUND_ROWS;
is_union_select= is_union() || fake_select_lex;
/*
If we are reading UNION output and the UNION is in the
IN/ANY/ALL/EXISTS subquery, then ORDER BY is redundant and hence should
be removed.
Example:
select ... col IN (select col2 FROM t1 union select col3 from t2 ORDER BY 1)
(as for ORDER BY ... LIMIT, it currently not supported inside
IN/ALL/ANY subqueries)
(For non-UNION this removal of ORDER BY clause is done in
check_and_do_in_subquery_rewrites())
*/
if (is_union() && item &&
(item->is_in_predicate() || item->is_exists_predicate()))
{
global_parameters()->order_list.first= NULL;
global_parameters()->order_list.elements= 0;
}
/* Global option */
if (is_union_select)