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.

1 files changed, 60 insertions, 0 deletions

diff --git a/mysql-test/t/group_min_max.test b/mysql-test/t/group_min_max.test
index 08f0f54df60..5ed082f7583 100644
--- a/mysql-test/t/group_min_max.test
+++ b/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;