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MDEV-28871: Assert ... failed in JOIN::dbug_verify_sj_inner_tables...

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optimize_semi_joins() calls update_sj_state() to update semi-join
optimization state in the JOIN class.

greedy_search() algorithm considers different join prefixes,
and then picks one table to put into the join prefix.
Most of the semi-join optimization state is in the table's entry
in the join->positions[cur_prefix_size].

However, it also needs to call update_sj_state() to update the
semi-join optimization state in the JOIN class.

There is one exception, which is the cause of this bug: when we're
inside optimize_semi_join_nests() and are optimizing a subquery,
optimize_semi_joins() does nothing, it doesn't call update_sj_state().

greedy_search() must not do that either.
This commit is contained in:
Sergei Petrunia
2022-07-07 22:15:42 +03:00
parent 66c06735a2
commit 0e9a255ec8
5 changed files with 46 additions and 1 deletions
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17
mysql-test/main/subselect_sj.test
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@ -3016,5 +3016,22 @@ EXECUTE stmt;
DROP TABLE t1, t2;
--echo #
--echo # MDEV-28871: Assert ... failed in JOIN::dbug_verify_sj_inner_tables with low optimizer_search_depth
--echo #
set @tmp_28871=@@optimizer_search_depth;
CREATE TABLE t1 (a INT);
CREATE TABLE t2 (b INT);
# Data is optional, fails either way
INSERT INTO t1 VALUES (1),(2);
INSERT INTO t1 VALUES (3),(4);
SET optimizer_search_depth= 1;
SELECT * FROM t1 WHERE a IN (SELECT b FROM t2 JOIN t1);
DROP TABLE t1, t2;
set optimizer_search_depth= @tmp_28871;
# The following command must be the last one the file
set optimizer_switch=@subselect_sj_tmp;