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MDEV-31279 Crash when lateral derived is guaranteed to return no rows

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Consider this query
SELECT t1.* FROM t1, (SELECT t2.b FROM t2 WHERE NOT EXISTS
(SELECT 1 FROM t3) GROUP BY b) sq where sq.b = t1.a;

If SELECT 1 FROM t3 is expensive, for example t3 has >
thd->variables.expensive_subquery_limit, first evaluation is deferred to
mysql_derived_fill().  There it is noted that, in the above case
 NOT EXISTS (SELECT 1 FROM t3) is constant and false.

This causes the join variable zero_result_cause to be set to
"Impossible WHERE noticed after reading const tables" and the handler
for this join is never "opened" via handler::ha_open.

When mysql_derived_fill() is called for the next group of results, this
unopened handler is not taken into account.

reviewed by Igor Babaev (igor@mariadb.com)
This commit is contained in:
Rex
2023-10-11 15:05:58 +12:00
committed by Rex Johnston
parent c17aca2f11
commit b4712242dd
3 changed files with 36 additions and 0 deletions
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15
mysql-test/main/derived_split_innodb.result
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@ -826,4 +826,19 @@ SELECT * FROM t1 JOIN t2 WHERE (t1.a, t2.b) IN (SELECT * FROM v);
a b
DROP VIEW v;
DROP TABLE t1, t2, t3;
#
# MDEV-31279 Crash when lateral derived is guaranteed to return no rows
#
CREATE TABLE t1 (a CHAR(1)) ENGINE=MyISAM;
INSERT INTO t1 VALUES ('1'),('2');
CREATE TABLE t2 (b INT, KEY(b)) ENGINE=MyISAM;
ALTER TABLE t2 DISABLE KEYS;
INSERT INTO t2 VALUES (1),(2),(3);
ALTER TABLE t2 ENABLE KEYS;
CREATE TABLE t3 (c INT) ENGINE=MyISAM;
INSERT INTO t3 (c) SELECT seq FROM seq_1_to_101;
SELECT * FROM t1 WHERE t1.a IN (SELECT b FROM
(SELECT t2.b FROM t2 WHERE NOT EXISTS (SELECT 1 FROM t3) GROUP BY b) sq);
a
DROP TABLE t1, t2, t3;
# End of 10.4 tests