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Backport into build-200911241145-5.1.40sp1

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> ------------------------------------------------------------
> revno: 3181
> revision-id: alexey.kopytov@sun.com-20091016201951-fsht0wm8xn8vkzsx
> parent: joerg@mysql.com-20091016164025-kb4sbrggq5o7zufc
> committer: Alexey Kopytov <Alexey.Kopytov@Sun.com>
> branch nick: mysql-5.1-bugteam
> timestamp: Sat 2009-10-17 00:19:51 +0400
> message:
>   Bug #47123: Endless 100% CPU loop with STRAIGHT_JOIN 
>    
>   The problem was in incorrect handling of predicates involving 
>   NULL as a constant value by the range optimizer. 
>    
>   For example, when creating a SEL_ARG node from a condition of 
>   the form "field < const" (which would normally result in the 
>   "NULL < field < const" SEL_ARG),  the special case when "const" 
>   is NULL was not taken into account, so "NULL < field < NULL" 
>   was produced for the "field < NULL" condition. 
>    
>   As a result, SEL_ARG structures of this form could not be 
>   further optimized which in turn could lead to incorrectly 
>   constructed SEL_ARG trees. In particular, code assuming SEL_ARG 
>   structures to always form a sequence of ordered disjoint 
>   intervals could enter an infinite loop under some 
>   circumstances. 
>    
>   Fixed by changing get_mm_leaf() so that for any sargable 
>   predicate except "<=>" involving NULL as a constant, "empty" 
>   SEL_ARG is returned, since such a predicate is always false.
This commit is contained in:
MySQL Build Team 2009-11-25 18:11:54 +01:00
parent b84555efae
commit 233dc05f39
5 changed files with 30 additions and 4 deletions
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3
mysql-test/r/partition_pruning.result
View file

@ -1272,10 +1272,9 @@ INSERT INTO t1 VALUES (1, '2009-01-01'), (2, NULL);
# test with an invalid date, which lead to item->null_value is set.
EXPLAIN PARTITIONS SELECT * FROM t1 WHERE b < CAST('2009-04-99' AS DATETIME);
id select_type table partitions type possible_keys key key_len ref rows Extra
1 SIMPLE t1 p20090401 ALL NULL NULL NULL NULL 2 Using where
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
Warnings:
Warning 1292 Incorrect datetime value: '2009-04-99'
Warning 1292 Incorrect datetime value: '2009-04-99'
DROP TABLE t1;
CREATE TABLE t1
(a INT NOT NULL AUTO_INCREMENT,

8
mysql-test/r/range.result
View file

@ -1216,6 +1216,14 @@ select 'In following EXPLAIN the access method should be ref, #rows~=500 (and no
Z
In following EXPLAIN the access method should be ref, #rows~=500 (and not 2)
explain select * from t2 where a=1000 and b<11;
#
# Bug #47123: Endless 100% CPU loop with STRAIGHT_JOIN
#
CREATE TABLE t1(a INT, KEY(a));
INSERT INTO t1 VALUES (1), (NULL);
SELECT * FROM t1 WHERE a <> NULL and (a <> NULL or a <= NULL);
a
DROP TABLE t1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ref a a 5 const 502 Using where
drop table t1, t2;

3
mysql-test/r/subselect.result
View file

@ -4403,8 +4403,7 @@ FROM t1
WHERE a = 230;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
2 DEPENDENT SUBQUERY st1 index NULL a 5 NULL 2 Using index
2 DEPENDENT SUBQUERY st2 index b b 5 NULL 2 Using where; Using index; Using join buffer
2 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
SELECT MAX(b), (SELECT COUNT(*) FROM st1,st2 WHERE st2.b <= t1.b)
FROM t1
WHERE a = 230;

9
mysql-test/t/range.test
View file

@ -1043,6 +1043,15 @@ alter table t2 add index (a,b);
select 'In following EXPLAIN the access method should be ref, #rows~=500 (and not 2)' Z;
explain select * from t2 where a=1000 and b<11;
--echo #
--echo # Bug #47123: Endless 100% CPU loop with STRAIGHT_JOIN
--echo #
CREATE TABLE t1(a INT, KEY(a));
INSERT INTO t1 VALUES (1), (NULL);
SELECT * FROM t1 WHERE a <> NULL and (a <> NULL or a <= NULL);
DROP TABLE t1;
drop table t1, t2;

11
sql/opt_range.cc
View file

@ -5911,6 +5911,17 @@ get_mm_leaf(RANGE_OPT_PARAM *param, COND *conf_func, Field *field,
goto end;
}
field->table->in_use->variables.sql_mode= orig_sql_mode;
/*
Any sargable predicate except "<=>" involving NULL as a constant is always
FALSE
*/
if (type != Item_func::EQUAL_FUNC && field->is_real_null())
{
tree= &null_element;
goto end;
}
str= (uchar*) alloc_root(alloc, key_part->store_length+1);
if (!str)
goto end;