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Fixed bug mdev-277 as part of the fix for lp:944706

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The cause for this bug is that the method JOIN::get_examined_rows iterates over all
JOIN_TABs of the join assuming they are just a sequence. In the query above, the
innermost subquery is merged into its parent query. When we call
JOIN::get_examined_rows for the second-level subquery, the iteration that
assumes sequential order of join tabs goes outside the join_tab array and calls
the method JOIN_TAB::get_examined_rows on uninitialized memory. 

The fix is to iterate over JOIN_TABs in a way that takes into account the nested
semi-join structure of JOIN_TABs. In particular iterate as select_describe.
This commit is contained in:
unknown
2012-05-18 14:52:01 +03:00
parent da5214831d
commit e5bca74bfb
7 changed files with 133 additions and 9 deletions
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19
mysql-test/t/subselect.test
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@ -5561,5 +5561,24 @@ WHERE alias1.a = alias2.a OR ('Moscow') IN ( SELECT a FROM t1 );
drop table t1;
--echo #
--echo # MDEV-277 CHEAP SQ: Server crashes in st_join_table::get_examined_rows
--echo # with semijoin+materialization, IN and = subqueries
--echo #
CREATE TABLE t1 (a1 INT);
INSERT INTO t1 VALUES (4),(6);
CREATE TABLE t2 (b1 INT);
INSERT INTO t2 VALUES (1),(7);
EXPLAIN
SELECT * FROM t1
WHERE a1 = (SELECT COUNT(*) FROM t1 WHERE a1 IN (SELECT a1 FROM t1, t2));
SELECT * FROM t1
WHERE a1 = (SELECT COUNT(*) FROM t1 WHERE a1 IN (SELECT a1 FROM t1, t2));
drop table t1, t2;
--echo # return optimizer switch changed in the beginning of this test
set optimizer_switch=@subselect_tmp;