Commit 50d85111 authored by gkodinov/kgeorge@magare.gmz's avatar gkodinov/kgeorge@magare.gmz
Browse files

Bug #32268: Indexed queries give bogus MIN and MAX results 

Loose index scan does the grouping so the temp table does 
not need to do it, even when sorting.
Fixed by checking if the grouping is already done before
doing sorting and grouping in a temp table and do only 
sorting.
parent 7b38492a

mysql-test/r/group_min_max.result

+46 −0
Original line number Diff line number Diff line
@@ -2307,3 +2307,49 @@ a 
2

4

DROP TABLE t1;

CREATE TABLE t1 (a INT, b INT);

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

INSERT INTO t1 SELECT a + 1, b FROM t1;

INSERT INTO t1 SELECT a + 2, b FROM t1;

EXPLAIN

SELECT a, MIN(b), MAX(b) FROM t1 GROUP BY a ORDER BY a DESC;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	12	Using temporary; Using filesort

SELECT a, MIN(b), MAX(b) FROM t1 GROUP BY a ORDER BY a DESC;

a	MIN(b)	MAX(b)

4	1	3

3	1	3

2	1	3

1	1	3

CREATE INDEX break_it ON t1 (a, b);

EXPLAIN

SELECT a, MIN(b), MAX(b) FROM t1 GROUP BY a ORDER BY a;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	range	NULL	break_it	10	NULL	7	Using index for group-by

SELECT a, MIN(b), MAX(b) FROM t1 GROUP BY a ORDER BY a;

a	MIN(b)	MAX(b)

1	1	3

2	1	3

3	1	3

4	1	3

EXPLAIN

SELECT a, MIN(b), MAX(b) FROM t1 GROUP BY a ORDER BY a DESC;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	range	NULL	break_it	10	NULL	7	Using index for group-by; Using temporary; Using filesort

SELECT a, MIN(b), MAX(b) FROM t1 GROUP BY a ORDER BY a DESC;

a	MIN(b)	MAX(b)

4	1	3

3	1	3

2	1	3

1	1	3

EXPLAIN

SELECT a, MIN(b), MAX(b), AVG(b) FROM t1 GROUP BY a ORDER BY a DESC;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	index	NULL	break_it	10	NULL	12	Using index

SELECT a, MIN(b), MAX(b), AVG(b) FROM t1 GROUP BY a ORDER BY a DESC;

a	MIN(b)	MAX(b)	AVG(b)

4	1	3	2.0000

3	1	3	2.0000

2	1	3	2.0000

1	1	3	2.0000

DROP TABLE t1;

mysql-test/t/group_min_max.test

+24 −0
Original line number Diff line number Diff line
@@ -888,7 +888,31 @@ SELECT SQL_BIG_RESULT DISTINCT(a) FROM t1; 


DROP TABLE t1;



#

# Bug #32268: Indexed queries give bogus MIN and MAX results

#



CREATE TABLE t1 (a INT, b INT);

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

INSERT INTO t1 SELECT a + 1, b FROM t1;

INSERT INTO t1 SELECT a + 2, b FROM t1;



EXPLAIN

SELECT a, MIN(b), MAX(b) FROM t1 GROUP BY a ORDER BY a DESC;

SELECT a, MIN(b), MAX(b) FROM t1 GROUP BY a ORDER BY a DESC;



CREATE INDEX break_it ON t1 (a, b);



EXPLAIN

SELECT a, MIN(b), MAX(b) FROM t1 GROUP BY a ORDER BY a;

SELECT a, MIN(b), MAX(b) FROM t1 GROUP BY a ORDER BY a;



EXPLAIN

SELECT a, MIN(b), MAX(b) FROM t1 GROUP BY a ORDER BY a DESC;

SELECT a, MIN(b), MAX(b) FROM t1 GROUP BY a ORDER BY a DESC;



EXPLAIN

SELECT a, MIN(b), MAX(b), AVG(b) FROM t1 GROUP BY a ORDER BY a DESC;

SELECT a, MIN(b), MAX(b), AVG(b) FROM t1 GROUP BY a ORDER BY a DESC;



DROP TABLE t1;

sql/sql_select.cc

+2 −1
Original line number Diff line number Diff line
@@ -10256,7 +10256,8 @@ Next_select_func setup_end_select_func(JOIN *join) 
  /* Set up select_end */

  if (table)

  {

    if (table->group && tmp_tbl->sum_func_count)

    if (table->group && tmp_tbl->sum_func_count && 

        !tmp_tbl->precomputed_group_by)

    {

      if (table->s->keys)

      {