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Bug#46051: Incorrectly market field caused wrong result.

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In a subselect all fields from outer selects are marked as dependent on
selects they are belong to. In some cases optimizer substitutes it for an
equivalent expression. For example "a_field IN (SELECT outer_field)" is
substituted with "a_field = outer_field". As we moved the outer_field to the
upper select it's not really outer anymore. But it was left marked as outer.
If exists an index over a_field optimizer choose wrong execution plan and thus
return wrong result.

Now the Item_in_subselect::single_value_transformer function removes dependent
marking from fields when a subselect is optimized away.
This commit is contained in:
Evgeny Potemkin
2009-07-16 19:43:46 +04:00
parent 6a7240b8d7
commit af2c91b701
3 changed files with 50 additions and 0 deletions
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26
mysql-test/r/subselect.result
View File

@@ -4452,4 +4452,30 @@ WHERE 1 IN (SELECT id FROM t1) WITH CHECK OPTION;
DELETE FROM v3;
DROP VIEW v1,v2,v3;
DROP TABLE t1,t2;
#
# Bug#45061: Incorrectly market field caused wrong result.
#
CREATE TABLE `C` (
`int_nokey` int(11) NOT NULL,
`int_key` int(11) NOT NULL,
KEY `int_key` (`int_key`)
);
INSERT INTO `C` VALUES (9,9), (0,0), (8,6), (3,6), (7,6), (0,4),
(1,7), (9,4), (0,8), (9,4), (0,7), (5,5), (0,0), (8,5), (8,7),
(5,2), (1,8), (7,0), (0,9), (9,5);
SELECT * FROM C WHERE `int_key` IN (SELECT `int_nokey`);
int_nokey int_key
9 9
0 0
5 5
0 0
EXPLAIN EXTENDED SELECT * FROM C WHERE `int_key` IN (SELECT `int_nokey`);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY C ALL NULL NULL NULL NULL 20 Using where
Warnings:
Note 1276 Field or reference 'test.C.int_nokey' of SELECT #2 was resolved in SELECT #1
Note 1249 Select 2 was reduced during optimization
Note 1003 select `test`.`C`.`int_nokey` AS `int_nokey`,`test`.`C`.`int_key` AS `int_key` from `test`.`C` where (`test`.`C`.`int_nokey` = `test`.`C`.`int_key`)
DROP TABLE C;
# End of test for bug#45061.
End of 5.0 tests.

20
mysql-test/t/subselect.test
View File

@@ -3428,4 +3428,24 @@ DELETE FROM v3;
DROP VIEW v1,v2,v3;
DROP TABLE t1,t2;
--echo #
--echo # Bug#45061: Incorrectly market field caused wrong result.
--echo #
CREATE TABLE `C` (
`int_nokey` int(11) NOT NULL,
`int_key` int(11) NOT NULL,
KEY `int_key` (`int_key`)
);
INSERT INTO `C` VALUES (9,9), (0,0), (8,6), (3,6), (7,6), (0,4),
(1,7), (9,4), (0,8), (9,4), (0,7), (5,5), (0,0), (8,5), (8,7),
(5,2), (1,8), (7,0), (0,9), (9,5);
SELECT * FROM C WHERE `int_key` IN (SELECT `int_nokey`);
EXPLAIN EXTENDED SELECT * FROM C WHERE `int_key` IN (SELECT `int_nokey`);
DROP TABLE C;
--echo # End of test for bug#45061.
--echo End of 5.0 tests.

4
sql/item_subselect.cc
View File

@@ -1145,6 +1145,10 @@ Item_in_subselect::single_value_transformer(JOIN *join,
else
{
// it is single select without tables => possible optimization
// remove the dependence mark since the item is moved to upper
// select and is not outer anymore.
item->walk(&Item::remove_dependence_processor,
(byte *) select_lex->outer_select());
item= func->create(left_expr, item);
// fix_field of item will be done in time of substituting
substitution= item;