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

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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.
This commit is contained in:
gkodinov/kgeorge@magare.gmz 2007-11-20 16:07:24 +02:00
parent 7b38492a4c
commit 50d8511136
3 changed files with 72 additions and 1 deletions
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46
mysql-test/r/group_min_max.result
View file

@ -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;

24
mysql-test/t/group_min_max.test
View file

@ -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;

3
sql/sql_select.cc
View file

@ -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)
{