Details
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Type:
Bug
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Status: Closed
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Priority:
Major
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Resolution: Fixed
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Affects Version/s: None
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Fix Version/s: None
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Component/s: None
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Labels:
Description
Not repeatable with maria-5.3 . The query below does not return any rows even though the row 8,8 matches both the ON and the WHERE predicates.
CREATE TABLE t1 ( f1 int(11), f2 int(11), f10 varchar(1), PRIMARY KEY (f1)) ;
INSERT INTO t1 VALUES (8,8,'u'),(10,5,'o');
SET SESSION optimizer_switch = 'materialization=off';
SELECT alias2.f1 , alias2.f2
FROM t1 AS alias1
RIGHT JOIN t1 AS alias2 ON alias2.f10
WHERE ( alias2.f1 , alias2.f2 ) IN ( SELECT f2 , f1 FROM t1 GROUP BY f2 , f1 );
explain:
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY alias2 ALL NULL NULL NULL NULL 2 Using where
1 PRIMARY alias1 index NULL PRIMARY 4 NULL 2 Using where; Using index
2 DEPENDENT SUBQUERY t1 ALL NULL NULL NULL NULL 2 Using filesort
correct result:
SET SESSION optimizer_switch = 'materialization=on';
SELECT alias2.f1 , alias2.f2 FROM t1 AS alias1 RIGHT JOIN t1 AS alias2 ON alias2.f10 WHERE ( alias2.f1 , alias2.f2 ) IN ( SELECT f2 , f1 FROM t1 GROUP BY f2 , f1 );
f1 f2
8 8
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Re: Wrong result with GROUP BY inside subquery and materialization=off in maria-5.3-mwl89
It turns out the bug is not specific to IN-TO-EXISTS. The following simple test case shows this:
CREATE TABLE t1 (f1a int, f2a int not null, f3a varchar(3) not null, PRIMARY KEY (f1a)) ;
INSERT INTO t1 VALUES
(8,8,'a1a'),
(10,5,'b1b');
CREATE TABLE t2 (f1b int, f2b int not null, f3b varchar(3) not null, PRIMARY KEY (f1b)) ;
INSERT INTO t2 VALUES
(10,5,'d1d');
SET @@optimizer_switch = 'materialization=off,subquery_cache=off';
– wrong empty result
SELECT * FROM t2 WHERE (f1b, f2b) IN (SELECT f1a, f2a FROM t1 GROUP BY f1a, f2a);
SET @@optimizer_switch = 'materialization=on,subquery_cache=off';
– wrong empty result
SELECT * FROM t2 WHERE (f1b, f2b) IN (SELECT f1a, f2a FROM t1 GROUP BY f1a, f2a);
Launchpad bug id: 715069
Re: Wrong result with GROUP BY inside subquery and materialization=off in maria-5.3-mwl89
The bug is specific to the in-to-exists strategy. A simpler example:
SELECT alias2.f1 FROM t1 AS alias1 right JOIN t1 AS alias2 ON alias2.f10
WHERE ( alias2.f1 ) IN ( SELECT f2 FROM t1 GROUP BY f2, f1);