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BKA join cache buffer is employed despite join_cache_level=3 (flat BNLH)

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In the `check_join_cache_usage()` function there is a branching issue
where an accidental fall-through to BKA/BKAH buffers may occur, even
when the join_cache_level setting does not permit their use.

This patch corrects the condition to ensure that BKA/BKAH join caching
is only enabled when explicitly allowed by join_cache_level

Reviewer: Sergei Petrunia <sergey@mariadb.com>
This commit is contained in:
Oleg Smirnov 2025-02-26 17:57:43 +07:00
commit 733852d4c3
3 changed files with 54 additions and 1 deletions
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26
mysql-test/main/join_cache.result
View file

@ -6443,3 +6443,29 @@ DROP TABLE t1, t2;
#
# End of 10.5 tests
#
#
# MDEV-36165: BKA join cache buffer is employed despite join_cache_level=3 (flat BNLH)
#
CREATE TABLE t1(a INT);
INSERT INTO t1 VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
CREATE TABLE t2(a INT, b INT);
INSERT INTO t2 SELECT a, a from t1;
CREATE TABLE t3(a INT, b INT, c INT, key (a,b));
INSERT INTO t3 select a, a, a FROM t1;
SET optimizer_switch = 'join_cache_hashed=off,join_cache_bka=on,mrr=on';
SET join_cache_level = 3;
EXPLAIN SELECT * FROM t2, t3 WHERE t2.a=t3.a AND (t3.b+1 <= t2.b+1);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 10 Using where
1 SIMPLE t3 ref a a 5 test.t2.a 1 Using index condition
SET join_cache_level = 4;
EXPLAIN SELECT * FROM t2, t3 WHERE t2.a=t3.a AND (t3.b+1 <= t2.b+1);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 10 Using where
1 SIMPLE t3 ref a a 5 test.t2.a 1 Using index condition
SET join_cache_level = default;
SET optimizer_switch = default;
DROP TABLE t1, t2, t3;
#
# End of 10.11 tests
#

27
mysql-test/main/join_cache.test
View file

@ -4321,3 +4321,30 @@ DROP TABLE t1, t2;
--echo #
--echo # End of 10.5 tests
--echo #
--echo #
--echo # MDEV-36165: BKA join cache buffer is employed despite join_cache_level=3 (flat BNLH)
--echo #
--source include/have_sequence.inc
CREATE TABLE t1(a INT);
INSERT INTO t1 VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
CREATE TABLE t2(a INT, b INT);
INSERT INTO t2 SELECT a, a from t1;
CREATE TABLE t3(a INT, b INT, c INT, key (a,b));
INSERT INTO t3 select a, a, a FROM t1;
SET optimizer_switch = 'join_cache_hashed=off,join_cache_bka=on,mrr=on';
SET join_cache_level = 3;
EXPLAIN SELECT * FROM t2, t3 WHERE t2.a=t3.a AND (t3.b+1 <= t2.b+1);
SET join_cache_level = 4;
EXPLAIN SELECT * FROM t2, t3 WHERE t2.a=t3.a AND (t3.b+1 <= t2.b+1);
SET join_cache_level = default;
SET optimizer_switch = default;
DROP TABLE t1, t2, t3;
--echo #
--echo # End of 10.11 tests
--echo #

2
sql/sql_select.cc
View file

@ -14769,7 +14769,7 @@ uint check_join_cache_usage(JOIN_TAB *tab,
}
goto no_join_cache;
}
if (cache_level > 4 && no_bka_cache)
if (cache_level < 5 || no_bka_cache)
goto no_join_cache;
if ((flags & HA_MRR_NO_ASSOCIATION) &&