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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.
This commit is contained in:
unknown
@ -2162,3 +2162,127 @@ SELECT MIN(c) FROM t2 WHERE b = 2 and a = 1 and c > 1 GROUP BY a;
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MIN(c)
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2
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DROP TABLE t1,t2;
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CREATE TABLE t1 (a INT, b INT, INDEX (a,b));
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INSERT INTO t1 (a, b) VALUES (1,1), (1,2), (1,3), (1,4), (1,5),
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(2,2), (2,3), (2,1), (3,1), (4,1), (4,2), (4,3), (4,4), (4,5), (4,6);
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EXPLAIN SELECT max(b), a FROM t1 GROUP BY a;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range NULL a 5 NULL 8 Using index for group-by
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FLUSH STATUS;
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SELECT max(b), a FROM t1 GROUP BY a;
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max(b) a
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5 1
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3 2
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1 3
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6 4
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SHOW STATUS LIKE 'handler_read__e%';
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Variable_name Value
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Handler_read_key 8
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Handler_read_next 0
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EXPLAIN SELECT max(b), a FROM t1 GROUP BY a;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range NULL a 5 NULL 8 Using index for group-by
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FLUSH STATUS;
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CREATE TABLE t2 SELECT max(b), a FROM t1 GROUP BY a;
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SHOW STATUS LIKE 'handler_read__e%';
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Variable_name Value
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Handler_read_key 8
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Handler_read_next 0
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FLUSH STATUS;
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SELECT * FROM (SELECT max(b), a FROM t1 GROUP BY a) b;
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max(b) a
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5 1
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3 2
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1 3
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6 4
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SHOW STATUS LIKE 'handler_read__e%';
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Variable_name Value
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Handler_read_key 8
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Handler_read_next 0
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FLUSH STATUS;
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(SELECT max(b), a FROM t1 GROUP BY a) UNION
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(SELECT max(b), a FROM t1 GROUP BY a);
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max(b) a
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5 1
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3 2
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1 3
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6 4
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SHOW STATUS LIKE 'handler_read__e%';
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Variable_name Value
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Handler_read_key 16
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Handler_read_next 0
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EXPLAIN (SELECT max(b), a FROM t1 GROUP BY a) UNION
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(SELECT max(b), a FROM t1 GROUP BY a);
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY t1 range NULL a 5 NULL 8 Using index for group-by
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2 UNION t1 range NULL a 5 NULL 8 Using index for group-by
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NULL UNION RESULT <union1,2> ALL NULL NULL NULL NULL NULL
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EXPLAIN SELECT (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) x
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FROM t1 AS t1_outer;
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY t1_outer index NULL a 10 NULL 15 Using index
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2 SUBQUERY t1 range NULL a 5 NULL 8 Using index for group-by
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EXPLAIN SELECT 1 FROM t1 AS t1_outer WHERE EXISTS
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(SELECT max(b) FROM t1 GROUP BY a HAVING a < 2);
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY t1_outer index NULL a 10 NULL 15 Using index
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2 SUBQUERY t1 index NULL a 10 NULL 8 Using index
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EXPLAIN SELECT 1 FROM t1 AS t1_outer WHERE
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(SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) > 12;
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE
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2 SUBQUERY t1 range NULL a 5 NULL 8 Using index for group-by
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EXPLAIN SELECT 1 FROM t1 AS t1_outer WHERE
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a IN (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2);
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY t1_outer index NULL a 10 NULL 15 Using where; Using index
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2 DEPENDENT SUBQUERY t1 index NULL a 10 NULL 8 Using index
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EXPLAIN SELECT 1 FROM t1 AS t1_outer GROUP BY a HAVING
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a > (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2);
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY t1_outer range NULL a 5 NULL 8 Using index for group-by
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2 SUBQUERY t1 range NULL a 5 NULL 8 Using index for group-by
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EXPLAIN SELECT 1 FROM t1 AS t1_outer1 JOIN t1 AS t1_outer2
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ON t1_outer1.a = (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2)
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AND t1_outer1.b = t1_outer2.b;
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY t1_outer1 ref a a 5 const 1 Using where; Using index
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1 PRIMARY t1_outer2 index NULL a 10 NULL 15 Using where; Using index
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2 SUBQUERY t1 range NULL a 5 NULL 8 Using index for group-by
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EXPLAIN SELECT (SELECT (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) x
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FROM t1 AS t1_outer) x2 FROM t1 AS t1_outer2;
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY t1_outer2 index NULL a 10 NULL 15 Using index
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2 SUBQUERY t1_outer index NULL a 10 NULL 15 Using index
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3 SUBQUERY t1 range NULL a 5 NULL 8 Using index for group-by
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CREATE TABLE t3 LIKE t1;
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FLUSH STATUS;
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INSERT INTO t3 SELECT a,MAX(b) FROM t1 GROUP BY a;
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SHOW STATUS LIKE 'handler_read__e%';
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Variable_name Value
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Handler_read_key 8
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Handler_read_next 0
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DELETE FROM t3;
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FLUSH STATUS;
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INSERT INTO t3 SELECT 1, (SELECT MAX(b) FROM t1 GROUP BY a HAVING a < 2)
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FROM t1 LIMIT 1;
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SHOW STATUS LIKE 'handler_read__e%';
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Variable_name Value
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Handler_read_key 8
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Handler_read_next 0
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FLUSH STATUS;
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DELETE FROM t3 WHERE (SELECT MAX(b) FROM t1 GROUP BY a HAVING a < 2) > 10000;
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SHOW STATUS LIKE 'handler_read__e%';
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Variable_name Value
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Handler_read_key 8
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Handler_read_next 0
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FLUSH STATUS;
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DELETE FROM t3 WHERE (SELECT (SELECT MAX(b) FROM t1 GROUP BY a HAVING a < 2) x
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FROM t1) > 10000;
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Warnings:
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Error 1242 Subquery returns more than 1 row
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SHOW STATUS LIKE 'handler_read__e%';
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Variable_name Value
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Handler_read_key 8
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Handler_read_next 1
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DROP TABLE t1,t2,t3;
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@ -810,3 +810,63 @@ explain SELECT MIN(c) FROM t2 WHERE b = 2 and a = 1 and c > 1 GROUP BY a;
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SELECT MIN(c) FROM t2 WHERE b = 2 and a = 1 and c > 1 GROUP BY a;
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DROP TABLE t1,t2;
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#
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# Bug#24156: Loose index scan not used with CREATE TABLE ...SELECT and similar statements
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#
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CREATE TABLE t1 (a INT, b INT, INDEX (a,b));
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INSERT INTO t1 (a, b) VALUES (1,1), (1,2), (1,3), (1,4), (1,5),
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(2,2), (2,3), (2,1), (3,1), (4,1), (4,2), (4,3), (4,4), (4,5), (4,6);
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EXPLAIN SELECT max(b), a FROM t1 GROUP BY a;
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FLUSH STATUS;
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SELECT max(b), a FROM t1 GROUP BY a;
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SHOW STATUS LIKE 'handler_read__e%';
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EXPLAIN SELECT max(b), a FROM t1 GROUP BY a;
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FLUSH STATUS;
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CREATE TABLE t2 SELECT max(b), a FROM t1 GROUP BY a;
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SHOW STATUS LIKE 'handler_read__e%';
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FLUSH STATUS;
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SELECT * FROM (SELECT max(b), a FROM t1 GROUP BY a) b;
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SHOW STATUS LIKE 'handler_read__e%';
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FLUSH STATUS;
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(SELECT max(b), a FROM t1 GROUP BY a) UNION
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(SELECT max(b), a FROM t1 GROUP BY a);
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SHOW STATUS LIKE 'handler_read__e%';
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EXPLAIN (SELECT max(b), a FROM t1 GROUP BY a) UNION
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(SELECT max(b), a FROM t1 GROUP BY a);
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EXPLAIN SELECT (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) x
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FROM t1 AS t1_outer;
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EXPLAIN SELECT 1 FROM t1 AS t1_outer WHERE EXISTS
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(SELECT max(b) FROM t1 GROUP BY a HAVING a < 2);
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EXPLAIN SELECT 1 FROM t1 AS t1_outer WHERE
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(SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) > 12;
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EXPLAIN SELECT 1 FROM t1 AS t1_outer WHERE
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a IN (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2);
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EXPLAIN SELECT 1 FROM t1 AS t1_outer GROUP BY a HAVING
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a > (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2);
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EXPLAIN SELECT 1 FROM t1 AS t1_outer1 JOIN t1 AS t1_outer2
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ON t1_outer1.a = (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2)
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AND t1_outer1.b = t1_outer2.b;
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EXPLAIN SELECT (SELECT (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) x
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FROM t1 AS t1_outer) x2 FROM t1 AS t1_outer2;
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CREATE TABLE t3 LIKE t1;
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FLUSH STATUS;
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INSERT INTO t3 SELECT a,MAX(b) FROM t1 GROUP BY a;
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SHOW STATUS LIKE 'handler_read__e%';
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DELETE FROM t3;
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FLUSH STATUS;
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INSERT INTO t3 SELECT 1, (SELECT MAX(b) FROM t1 GROUP BY a HAVING a < 2)
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FROM t1 LIMIT 1;
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SHOW STATUS LIKE 'handler_read__e%';
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FLUSH STATUS;
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DELETE FROM t3 WHERE (SELECT MAX(b) FROM t1 GROUP BY a HAVING a < 2) > 10000;
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SHOW STATUS LIKE 'handler_read__e%';
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FLUSH STATUS;
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DELETE FROM t3 WHERE (SELECT (SELECT MAX(b) FROM t1 GROUP BY a HAVING a < 2) x
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FROM t1) > 10000;
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SHOW STATUS LIKE 'handler_read__e%';
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DROP TABLE t1,t2,t3;
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