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.

mysql-test/r/group_min_max.result

@@ -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

@@ -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

@@ -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,