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Bug#21174: Index degrades sort performance and optimizer does not honor IGNORE INDEX

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- fix moved to 5.1
This commit is contained in:
gkodinov/kgeorge@macbook.gmz 2006-09-27 13:11:00 +03:00
parent a01e7b12ce
commit 24c5bf6a96
3 changed files with 23 additions and 0 deletions
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9
mysql-test/r/group_by.result
View file

@ -821,3 +821,12 @@ a b real_b
68 France France
DROP VIEW v1;
DROP TABLE t1,t2;
CREATE TABLE t1 (a INT, b INT, KEY(a));
INSERT INTO t1 VALUES (1, 1), (2, 2), (3,3), (4,4);
EXPLAIN SELECT a, SUM(b) FROM t1 GROUP BY a LIMIT 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL a 5 NULL 4
EXPLAIN SELECT a, SUM(b) FROM t1 IGNORE INDEX (a) GROUP BY a LIMIT 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 4 Using temporary; Using filesort
DROP TABLE t1;

12
mysql-test/t/group_by.test
View file

@ -655,3 +655,15 @@ where t2.b=v1.a GROUP BY t2.b;
DROP VIEW v1;
DROP TABLE t1,t2;
#
# Bug #21174: Index degrades sort performance and
# optimizer does not honor IGNORE INDEX
#
CREATE TABLE t1 (a INT, b INT, KEY(a));
INSERT INTO t1 VALUES (1, 1), (2, 2), (3,3), (4,4);
EXPLAIN SELECT a, SUM(b) FROM t1 GROUP BY a LIMIT 2;
EXPLAIN SELECT a, SUM(b) FROM t1 IGNORE INDEX (a) GROUP BY a LIMIT 2;
DROP TABLE t1;

2
sql/sql_select.cc
View file

@ -11875,6 +11875,8 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
We must not try to use disabled keys.
*/
usable_keys= table->s->keys_in_use;
/* we must not consider keys that are disabled by IGNORE INDEX */
usable_keys.intersect(table->keys_in_use_for_query);
for (ORDER *tmp_order=order; tmp_order ; tmp_order=tmp_order->next)
{