mirror/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-01-31 02:51:44 +01:00
Code Issues Projects Releases Packages Wiki Activity Actions

backport from 6.0:

Browse source 
Bug #40925: Equality propagation takes non indexed attribute

Query execution plans and execution time of queries like

  select a, b, c from t1
    where a > '2008-11-21' and b = a limit 10

depended on the order of equality operator parameters:
"b = a" and "a = b" are not same. 


An equality propagation algorithm has been fixed:
the substitute_for_best_equal_field function should not
substitute a field for an equal field if both fields belong
to the same table.
This commit is contained in:
Gleb Shchepa 2009-04-28 05:19:13 +05:00
parent 3df4ad8a5d
commit fa01a4ed26
3 changed files with 28 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

13
mysql-test/r/select.result
View file

@ -4388,4 +4388,17 @@ f3 f4 count
1 abc 1
1 def 2
drop table t1, t2, t3;
CREATE TABLE t1 (a INT KEY, b INT);
INSERT INTO t1 VALUES (1,1), (2,2), (3,3), (4,4);
EXPLAIN EXTENDED SELECT a, b FROM t1 WHERE a > 1 AND a = b LIMIT 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range PRIMARY PRIMARY 4 NULL 3 Using where
Warnings:
Note 1003 select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where ((`test`.`t1`.`b` = `test`.`t1`.`a`) and (`test`.`t1`.`a` > 1)) limit 2
EXPLAIN EXTENDED SELECT a, b FROM t1 WHERE a > 1 AND b = a LIMIT 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range PRIMARY PRIMARY 4 NULL 3 Using where
Warnings:
Note 1003 select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where ((`test`.`t1`.`a` = `test`.`t1`.`b`) and (`test`.`t1`.`a` > 1)) limit 2
DROP TABLE t1;
End of 5.0 tests

14
mysql-test/t/select.test
View file

@ -3737,4 +3737,18 @@ cr.f4 = cr2.f4
GROUP BY a.f3, cr.f4;
drop table t1, t2, t3;
#
# Bug #40925: Equality propagation takes non indexed attribute
#
CREATE TABLE t1 (a INT KEY, b INT);
INSERT INTO t1 VALUES (1,1), (2,2), (3,3), (4,4);
EXPLAIN EXTENDED SELECT a, b FROM t1 WHERE a > 1 AND a = b LIMIT 2;
EXPLAIN EXTENDED SELECT a, b FROM t1 WHERE a > 1 AND b = a LIMIT 2;
DROP TABLE t1;
--echo End of 5.0 tests

2
sql/item.cc
View file

@ -4341,7 +4341,7 @@ Item *Item_field::replace_equal_field(byte *arg)
return const_item;
}
Item_field *subst= item_equal->get_first();
if (subst && !field->eq(subst->field))
if (subst && field->table != subst->field->table && !field->eq(subst->field))
return subst;
}
return this;