Commit 762f4ac1 authored by unknown's avatar unknown
Browse files

Bug#24156: Loose index scan not used with CREATE TABLE ...SELECT and similar 

           statements
Currently the optimizer evaluates loose index scan only for top-level SELECT
statements
Extend loose index scan applicability by :
 - Test the applicability of loose scan for each sub-select, instead of the
   whole query. This change enables loose index scan for sub-queries.
 - allow non-select statements with SELECT parts (like, e.g. 
   CREATE TABLE .. SELECT ...) to use loose index scan.


mysql-test/r/group_min_max.result:
  Bug#24156: Loose index scan not used with CREATE TABLE ...SELECT and similar
             statements
   - test case
mysql-test/t/group_min_max.test:
  Bug#24156: Loose index scan not used with CREATE TABLE ...SELECT and similar
             statements
   - test case
sql/opt_range.cc:
  Bug#24156: Loose index scan not used with CREATE TABLE ...SELECT and similar
             statements
   - loose index scan will be tried over the current subselect 
     (lex->current_select) instead of the whole query (lex->select_lex).
   - allow non-select statements with SELECT parts (like, e.g. 
     CREATE TABLE .. SELECT ...) to use loose index scan.
parent 3ebdcee5

mysql-test/r/group_min_max.result

+124 −0
Original line number Diff line number Diff line
@@ -2162,3 +2162,127 @@ SELECT MIN(c) FROM t2 WHERE b = 2 and a = 1 and c > 1 GROUP BY a; 
MIN(c)

2

DROP TABLE t1,t2;

CREATE TABLE t1 (a INT, b INT, INDEX (a,b));

INSERT INTO t1 (a, b) VALUES (1,1), (1,2), (1,3), (1,4), (1,5),

(2,2), (2,3), (2,1), (3,1), (4,1), (4,2), (4,3), (4,4), (4,5), (4,6);

EXPLAIN SELECT max(b), a FROM t1 GROUP BY a;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	range	NULL	a	5	NULL	8	Using index for group-by

FLUSH STATUS;

SELECT max(b), a FROM t1 GROUP BY a;

max(b)	a

5	1

3	2

1	3

6	4

SHOW STATUS LIKE 'handler_read__e%';

Variable_name	Value

Handler_read_key	8

Handler_read_next	0

EXPLAIN SELECT max(b), a FROM t1 GROUP BY a;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	range	NULL	a	5	NULL	8	Using index for group-by

FLUSH STATUS;

CREATE TABLE t2 SELECT max(b), a FROM t1 GROUP BY a;

SHOW STATUS LIKE 'handler_read__e%';

Variable_name	Value

Handler_read_key	8

Handler_read_next	0

FLUSH STATUS;

SELECT * FROM (SELECT max(b), a FROM t1 GROUP BY a) b;

max(b)	a

5	1

3	2

1	3

6	4

SHOW STATUS LIKE 'handler_read__e%';

Variable_name	Value

Handler_read_key	8

Handler_read_next	0

FLUSH STATUS;

(SELECT max(b), a FROM t1 GROUP BY a) UNION 

(SELECT max(b), a FROM t1 GROUP BY a);

max(b)	a

5	1

3	2

1	3

6	4

SHOW STATUS LIKE 'handler_read__e%';

Variable_name	Value

Handler_read_key	16

Handler_read_next	0

EXPLAIN (SELECT max(b), a FROM t1 GROUP BY a) UNION 

(SELECT max(b), a FROM t1 GROUP BY a);

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	PRIMARY	t1	range	NULL	a	5	NULL	8	Using index for group-by

2	UNION	t1	range	NULL	a	5	NULL	8	Using index for group-by

NULL	UNION RESULT	<union1,2>	ALL	NULL	NULL	NULL	NULL	NULL	

EXPLAIN SELECT (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) x

FROM t1 AS t1_outer;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	PRIMARY	t1_outer	index	NULL	a	10	NULL	15	Using index

2	SUBQUERY	t1	range	NULL	a	5	NULL	8	Using index for group-by

EXPLAIN SELECT 1 FROM t1 AS t1_outer WHERE EXISTS 

(SELECT max(b) FROM t1 GROUP BY a HAVING a < 2);

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	PRIMARY	t1_outer	index	NULL	a	10	NULL	15	Using index

2	SUBQUERY	t1	index	NULL	a	10	NULL	8	Using index

EXPLAIN SELECT 1 FROM t1 AS t1_outer WHERE 

(SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) > 12;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE

2	SUBQUERY	t1	range	NULL	a	5	NULL	8	Using index for group-by

EXPLAIN SELECT 1 FROM t1 AS t1_outer WHERE 

a IN (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2);

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	PRIMARY	t1_outer	index	NULL	a	10	NULL	15	Using where; Using index

2	DEPENDENT SUBQUERY	t1	index	NULL	a	10	NULL	8	Using index

EXPLAIN SELECT 1 FROM t1 AS t1_outer GROUP BY a HAVING 

a > (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2);

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	PRIMARY	t1_outer	range	NULL	a	5	NULL	8	Using index for group-by

2	SUBQUERY	t1	range	NULL	a	5	NULL	8	Using index for group-by

EXPLAIN SELECT 1 FROM t1 AS t1_outer1 JOIN t1 AS t1_outer2 

ON t1_outer1.a = (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) 

AND t1_outer1.b = t1_outer2.b;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	PRIMARY	t1_outer1	ref	a	a	5	const	1	Using where; Using index

1	PRIMARY	t1_outer2	index	NULL	a	10	NULL	15	Using where; Using index

2	SUBQUERY	t1	range	NULL	a	5	NULL	8	Using index for group-by

EXPLAIN SELECT (SELECT (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) x

FROM t1 AS t1_outer) x2 FROM t1 AS t1_outer2;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	PRIMARY	t1_outer2	index	NULL	a	10	NULL	15	Using index

2	SUBQUERY	t1_outer	index	NULL	a	10	NULL	15	Using index

3	SUBQUERY	t1	range	NULL	a	5	NULL	8	Using index for group-by

CREATE TABLE t3 LIKE t1;

FLUSH STATUS;

INSERT INTO t3 SELECT a,MAX(b) FROM t1 GROUP BY a;

SHOW STATUS LIKE 'handler_read__e%';

Variable_name	Value

Handler_read_key	8

Handler_read_next	0

DELETE FROM t3;

FLUSH STATUS;

INSERT INTO t3 SELECT 1, (SELECT MAX(b) FROM t1 GROUP BY a HAVING a < 2) 

FROM t1 LIMIT 1;

SHOW STATUS LIKE 'handler_read__e%';

Variable_name	Value

Handler_read_key	8

Handler_read_next	0

FLUSH STATUS;

DELETE FROM t3 WHERE (SELECT MAX(b) FROM t1 GROUP BY a HAVING a < 2) > 10000;

SHOW STATUS LIKE 'handler_read__e%';

Variable_name	Value

Handler_read_key	8

Handler_read_next	0

FLUSH STATUS;

DELETE FROM t3 WHERE (SELECT (SELECT MAX(b) FROM t1 GROUP BY a HAVING a < 2) x 

FROM t1) > 10000;

Warnings:

Error	1242	Subquery returns more than 1 row

SHOW STATUS LIKE 'handler_read__e%';

Variable_name	Value

Handler_read_key	8

Handler_read_next	1

DROP TABLE t1,t2,t3;

mysql-test/t/group_min_max.test

+60 −0
Original line number Diff line number Diff line
@@ -810,3 +810,63 @@ explain SELECT MIN(c) FROM t2 WHERE b = 2 and a = 1 and c > 1 GROUP BY a; 
SELECT MIN(c) FROM t2 WHERE b = 2 and a = 1 and c > 1 GROUP BY a;



DROP TABLE t1,t2;



#

# Bug#24156: Loose index scan not used with CREATE TABLE ...SELECT and similar statements

#



CREATE TABLE t1 (a INT, b INT, INDEX (a,b));

INSERT INTO t1 (a, b) VALUES (1,1), (1,2), (1,3), (1,4), (1,5),

       (2,2), (2,3), (2,1), (3,1), (4,1), (4,2), (4,3), (4,4), (4,5), (4,6);

EXPLAIN SELECT max(b), a FROM t1 GROUP BY a;

FLUSH STATUS;

SELECT max(b), a FROM t1 GROUP BY a;

SHOW STATUS LIKE 'handler_read__e%';

EXPLAIN SELECT max(b), a FROM t1 GROUP BY a;

FLUSH STATUS;

CREATE TABLE t2 SELECT max(b), a FROM t1 GROUP BY a;

SHOW STATUS LIKE 'handler_read__e%';

FLUSH STATUS;

SELECT * FROM (SELECT max(b), a FROM t1 GROUP BY a) b;

SHOW STATUS LIKE 'handler_read__e%';

FLUSH STATUS;

(SELECT max(b), a FROM t1 GROUP BY a) UNION 

 (SELECT max(b), a FROM t1 GROUP BY a);

SHOW STATUS LIKE 'handler_read__e%';

EXPLAIN (SELECT max(b), a FROM t1 GROUP BY a) UNION 

 (SELECT max(b), a FROM t1 GROUP BY a);



EXPLAIN SELECT (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) x

  FROM t1 AS t1_outer;

EXPLAIN SELECT 1 FROM t1 AS t1_outer WHERE EXISTS 

  (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2);

EXPLAIN SELECT 1 FROM t1 AS t1_outer WHERE 

  (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) > 12;

EXPLAIN SELECT 1 FROM t1 AS t1_outer WHERE 

  a IN (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2);

EXPLAIN SELECT 1 FROM t1 AS t1_outer GROUP BY a HAVING 

  a > (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2);

EXPLAIN SELECT 1 FROM t1 AS t1_outer1 JOIN t1 AS t1_outer2 

   ON t1_outer1.a = (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) 

   AND t1_outer1.b = t1_outer2.b;

EXPLAIN SELECT (SELECT (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) x

  FROM t1 AS t1_outer) x2 FROM t1 AS t1_outer2;



CREATE TABLE t3 LIKE t1;

FLUSH STATUS;

INSERT INTO t3 SELECT a,MAX(b) FROM t1 GROUP BY a;

SHOW STATUS LIKE 'handler_read__e%';

DELETE FROM t3;

FLUSH STATUS;

INSERT INTO t3 SELECT 1, (SELECT MAX(b) FROM t1 GROUP BY a HAVING a < 2) 

  FROM t1 LIMIT 1;

SHOW STATUS LIKE 'handler_read__e%';

FLUSH STATUS;

DELETE FROM t3 WHERE (SELECT MAX(b) FROM t1 GROUP BY a HAVING a < 2) > 10000;

SHOW STATUS LIKE 'handler_read__e%';

FLUSH STATUS;

DELETE FROM t3 WHERE (SELECT (SELECT MAX(b) FROM t1 GROUP BY a HAVING a < 2) x 

                      FROM t1) > 10000;

SHOW STATUS LIKE 'handler_read__e%';



DROP TABLE t1,t2,t3;

sql/opt_range.cc

+3 −3
Original line number Diff line number Diff line
@@ -7445,7 +7445,7 @@ static TRP_GROUP_MIN_MAX * 
get_best_group_min_max(PARAM *param, SEL_TREE *tree)

{

  THD *thd= param->thd;

  JOIN *join= thd->lex->select_lex.join;

  JOIN *join= thd->lex->current_select->join;

  TABLE *table= param->table;

  bool have_min= FALSE;              /* TRUE if there is a MIN function. */

  bool have_max= FALSE;              /* TRUE if there is a MAX function. */
@@ -7466,7 +7466,7 @@ get_best_group_min_max(PARAM *param, SEL_TREE *tree) 
  DBUG_ENTER("get_best_group_min_max");



  /* Perform few 'cheap' tests whether this access method is applicable. */

  if (!join || (thd->lex->sql_command != SQLCOM_SELECT))

  if (!join)

    DBUG_RETURN(NULL);        /* This is not a select statement. */

  if ((join->tables != 1) ||  /* The query must reference one table. */

      ((!join->group_list) && /* Neither GROUP BY nor a DISTINCT query. */
@@ -8316,7 +8316,7 @@ TRP_GROUP_MIN_MAX::make_quick(PARAM *param, bool retrieve_full_rows, 
  DBUG_ENTER("TRP_GROUP_MIN_MAX::make_quick");



  quick= new QUICK_GROUP_MIN_MAX_SELECT(param->table,

                                        param->thd->lex->select_lex.join,

                                        param->thd->lex->current_select->join,

                                        have_min, have_max, min_max_arg_part,

                                        group_prefix_len, used_key_parts,

                                        index_info, index, read_cost, records,