Commit 6675c2c2 authored by unknown's avatar unknown
Browse files

Bug #21174: Index degrades sort performance and 

             optimizer does not honor IGNORE INDEX
 - Allow an index to be used for sorting the table 
   instead of filesort only if it is not disabled by
   IGNORE INDEX.


mysql-test/r/group_by.result:
  Bug #21174: Index degrades sort performance and 
               optimizer does not honor IGNORE INDEX
   - test case
mysql-test/t/group_by.test:
  Bug #21174: Index degrades sort performance and 
               optimizer does not honor IGNORE INDEX
   - test case
parent 759027d1

mysql-test/r/group_by.result

+9 −0
Original line number Diff line number Diff line
@@ -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;

mysql-test/t/group_by.test

+12 −0
Original line number Diff line number Diff line
@@ -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;

sql/sql_select.cc

+2 −0
Original line number Diff line number Diff line
@@ -11498,6 +11498,8 @@ 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)

  {