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MDEV-23723: Crash when test_if_skip_sort_order() is checked for derived ...

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The problem was caused by the following scenario:

Subquery's table has two indexes, KEY a(a), KEY a_b(a,b)

- LATERAL DERIVED optimization decides to use index a.
  = The subquery uses ref access over key a.
- test_if_skip_sort_order() sees that KEY a_b satisfies the
  subquery's GROUP BY clause, and attempts to switch to it.
  = It fails to do so, because KEYUSE objects for index a_b
    are switched off.

Fixed by disallowing to change the ref access key if it uses KEYUSE
objects injected by LATERAL DERIVED optimization.
This commit is contained in:
Sergei Petrunia
2021-04-29 19:30:07 +03:00
parent 8f9a72a150
commit 2820f30dde
4 changed files with 70 additions and 1 deletions
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34
mysql-test/main/derived_split_innodb.result
View File

@@ -140,3 +140,37 @@ id select_type table type possible_keys key key_len ref rows Extra
2 DERIVED t2 index NULL PRIMARY 4 NULL 3
drop view v1;
drop table t1,t2;
#
# MDEV-23723: Crash when test_if_skip_sort_order() is checked for derived table subject to split
#
CREATE TABLE t1 (a INT, b INT, KEY (a), KEY (a,b)) ENGINE=InnoDB;
CREATE TABLE t2 (c INT, KEY (c)) ENGINE=InnoDB;
SELECT * FROM t1 t1a JOIN t1 t1b;
a b a b
INSERT INTO t2 VALUES (1),(2);
INSERT INTO t1 VALUES (1,2),(3,4),(5,6),(7,8),(9,10),(11,12);
set statement optimizer_switch='split_materialized=off' for EXPLAIN
SELECT *
FROM
t1 JOIN
(SELECT t1.a, t1.b FROM t1, t2 WHERE t1.b = t2.c GROUP BY t1.a, t1.b) as dt
WHERE
t1.a = dt.a;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 index a,a_2 a_2 10 NULL 6 Using where; Using index
1 PRIMARY <derived2> ref key0 key0 5 test.t1.a 2
2 DERIVED t1 index NULL a_2 10 NULL 6 Using where; Using index
2 DERIVED t2 ref c c 5 test.t1.b 1 Using index
set statement optimizer_switch='split_materialized=on' for EXPLAIN
SELECT *
FROM
t1 JOIN
(SELECT t1.a, t1.b FROM t1, t2 WHERE t1.b = t2.c GROUP BY t1.a, t1.b) as dt
WHERE
t1.a = dt.a;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 index a,a_2 a_2 10 NULL 6 Using where; Using index
1 PRIMARY <derived2> ref key0 key0 5 test.t1.a 2
2 LATERAL DERIVED t1 ref a,a_2 a 5 test.t1.a 1 Using where; Using temporary; Using filesort
2 LATERAL DERIVED t2 ref c c 5 test.t1.b 1 Using index
DROP TABLE t1, t2;