Commit a52359e0 authored by unknown's avatar unknown
Browse files

Fix for BUG#10037 

* Add 0.01 to cost of 'range'+'using index' scan to avoid optimizer choice races with 
  'index' scan.


mysql-test/r/range.result:
  Update the test result after the changed cost
sql/opt_range.cc:
  Fix for BUG#10037
  * Add 0.01 to cost of 'range'+'using index' scan to avoid optimizer choice races with 
    'index' scan.
  * make QUICK_GROUP_MIN_MAX_SELECT handle the case where the source table is empty.
parent 241bedad

mysql-test/r/range.result

+2 −2
Original line number Diff line number Diff line
@@ -256,12 +256,12 @@ INSERT INTO t2 VALUES (0),(0),(1),(1),(2),(2); 
explain select * from t1, t2 where (t1.key1 <t2.keya + 1) and t2.keya=3;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t2	ref	j1	j1	4	const	1	Using index

1	SIMPLE	t1	range	i1	i1	4	NULL	7	Using where; Using index

1	SIMPLE	t1	index	i1	i1	4	NULL	7	Using where; Using index

explain select * from t1 force index(i1), t2 force index(j1) where 

(t1.key1 <t2.keya + 1) and t2.keya=3;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t2	ref	j1	j1	4	const	1	Using index

1	SIMPLE	t1	range	i1	i1	4	NULL	7	Using where; Using index

1	SIMPLE	t1	index	i1	i1	4	NULL	7	Using where; Using index

DROP TABLE t1,t2;

CREATE TABLE t1 (

a int(11) default NULL,

sql/opt_range.cc

+4 −1
Original line number Diff line number Diff line
@@ -2257,7 +2257,8 @@ inline double get_index_only_read_time(const PARAM* param, ha_rows records, 
			 param->table->file->ref_length) + 1);

  read_time=((double) (records+keys_per_block-1)/

             (double) keys_per_block);

  return read_time;

  /* Add 0.01 to avoid cost races between 'range' and 'index' */

  return read_time + 0.01;

}
@@ -7912,6 +7913,8 @@ int QUICK_GROUP_MIN_MAX_SELECT::reset(void) 
  file->extra(HA_EXTRA_KEYREAD); /* We need only the key attributes */

  result= file->ha_index_init(index);

  result= file->index_last(record);

  if (result == HA_ERR_END_OF_FILE)

    DBUG_RETURN(0);

  if (result)

    DBUG_RETURN(result);

  if (quick_prefix_select && quick_prefix_select->reset())