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Fixed LP bug #904345.

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The MIN/MAX optimizer code from the function opt_sum_query erroneously
did not take into account conjunctive conditions that did not depend on
any table, yet were not identified as constant items. These could be
items containing rand() or PS/SP parameters. These items are supposed
to be evaluated at the execution phase. That's why if such conditions
can be extracted from the WHERE condition the MIN/MAX optimization is
not applied as currently it is always done at the optimization phase.

(In 5.3 expensive subqueries are also evaluated only at the execution
phase. So, if a constant condition with such subquery can be extracted
from the WHERE clause the MIN/MAX optimization should not be applied 
in 5.3.)

IF an IN/ALL/SOME predicate with a constant left part is transformed
into an EXISTS subquery the resulting subquery should not be considered
uncacheable if the right part of the predicate is not uncacheable.

Backported the function dbug_print_item() from 5.3. The function is used
only for debugging.
This commit is contained in:
Igor Babaev 2011-12-27 13:19:13 -08:00
commit c9259f166b
12 changed files with 123 additions and 35 deletions
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8
mysql-test/r/select_pkeycache.result
View file

@ -2778,10 +2778,10 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
explain select max(key1) from t1 where key1 <= 0.6158 and rand() + 0.5 >= 0.5;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
1 SIMPLE t1 index key1 key1 5 NULL 4 Using where; Using index
explain select min(key1) from t1 where key1 >= 0.3762 and rand() + 0.5 >= 0.5;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
1 SIMPLE t1 range key1 key1 5 NULL 3 Using where; Using index
select max(key1) from t1 where key1 <= 0.6158;
max(key1)
0.615800023078918
@ -2800,10 +2800,10 @@ max(key1) min(key2)
0.615800023078918 1.37619996070862
select max(key1) from t1 where key1 <= 0.6158 and rand() + 0.5 >= 0.5;
max(key1)
0.615800023078918
0.384499996900558
select min(key1) from t1 where key1 >= 0.3762 and rand() + 0.5 >= 0.5;
min(key1)
0.376199990510941
0.384499996900558
DROP TABLE t1,t2;
CREATE TABLE t1 (i BIGINT UNSIGNED NOT NULL);
INSERT INTO t1 VALUES (10);