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Fix bug MDEV-641 

Analysis:
Range analysis discoveres that the query can be executed via loose index scan for GROUP BY.
Later, GROUP BY analysis fails to confirm that the GROUP operation can be computed via an
index because there is no logic to handle duplicate field references in the GROUP clause.
As a result the optimizer produces an inconsistent plan. It constructs a temporary table,
but on the other hand the group fields are not set to point there.
    
Solution:
Make loose scan analysis work in sync with order by analysis. In the case of duplicate
columns loose scan will not be applicable. This limitation will be lifted in 10.0 by
removing duplicate columns.
parent 7f208d3c
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mysql-test/r/group_by.result
View file @ 768b62fe
......@@ -1940,4 +1940,248 @@ Warning 1292 Truncated incorrect INTEGER value: 'K'
Warning 1292 Truncated incorrect INTEGER value: 'jxW<'
DROP TABLE t1;
SET SQL_BIG_TABLES=0;
#
# MDEV-641 LP:1002108 - Wrong result (or crash) from a query with duplicated field in the group list and a limit clause
# Bug#11761078: 53534: INCORRECT 'SELECT SQL_BIG_RESULT...'
# WITH GROUP BY ON DUPLICATED FIELDS
#
CREATE TABLE t1(
col1 int,
UNIQUE INDEX idx (col1));
INSERT INTO t1 VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10),
(11),(12),(13),(14),(15),(16),(17),(18),(19),(20);
EXPLAIN SELECT col1 AS field1, col1 AS field2
FROM t1 GROUP BY field1, field2;;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL idx 5 NULL 20 Using index; Using temporary; Using filesort
FLUSH STATUS;
SELECT col1 AS field1, col1 AS field2
FROM t1 GROUP BY field1, field2;;
field1 field2
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
10 10
11 11
12 12
13 13
14 14
15 15
16 16
17 17
18 18
19 19
20 20
SHOW SESSION STATUS LIKE 'Sort_scan%';
Variable_name Value
Sort_scan 1
EXPLAIN SELECT SQL_BIG_RESULT col1 AS field1, col1 AS field2
FROM t1 GROUP BY field1, field2;;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL idx 5 NULL 20 Using index; Using filesort
FLUSH STATUS;
SELECT SQL_BIG_RESULT col1 AS field1, col1 AS field2
FROM t1 GROUP BY field1, field2;;
field1 field2
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
10 10
11 11
12 12
13 13
14 14
15 15
16 16
17 17
18 18
19 19
20 20
SHOW SESSION STATUS LIKE 'Sort_scan%';
Variable_name Value
Sort_scan 1
CREATE VIEW v1 AS SELECT * FROM t1;
SELECT SQL_BIG_RESULT col1 AS field1, col1 AS field2
FROM v1
GROUP BY field1, field2;
field1 field2
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
10 10
11 11
12 12
13 13
14 14
15 15
16 16
17 17
18 18
19 19
20 20
SELECT SQL_BIG_RESULT tbl1.col1 AS field1, tbl2.col1 AS field2
FROM t1 as tbl1, t1 as tbl2
GROUP BY field1, field2
LIMIT 3;
field1 field2
1 1
1 2
1 3
explain
select col1 f1, col1 f2 from t1 order by f2, f1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL idx 5 NULL 20 Using index; Using filesort
select col1 f1, col1 f2 from t1 order by f2, f1;
f1 f2
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
10 10
11 11
12 12
13 13
14 14
15 15
16 16
17 17
18 18
19 19
20 20
explain
select col1 f1, col1 f2 from t1 group by f2 order by f2, f1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range NULL idx 5 NULL 7 Using index for group-by; Using temporary; Using filesort
select col1 f1, col1 f2 from t1 group by f2 order by f2, f1;
f1 f2
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
10 10
11 11
12 12
13 13
14 14
15 15
16 16
17 17
18 18
19 19
20 20
explain
select col1 f1, col1 f2 from t1 group by f1, f2 order by f2, f1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL idx 5 NULL 20 Using index; Using temporary; Using filesort
select col1 f1, col1 f2 from t1 group by f1, f2 order by f2, f1;
f1 f2
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
10 10
11 11
12 12
13 13
14 14
15 15
16 16
17 17
18 18
19 19
20 20
CREATE TABLE t2(
col1 int,
col2 int,
UNIQUE INDEX idx (col1, col2));
INSERT INTO t2(col1, col2) VALUES
(1,20),(2,19),(3,18),(4,17),(5,16),(6,15),(7,14),(8,13),(9,12),(10,11),
(11,10),(12,9),(13,8),(14,7),(15,6),(16,5),(17,4),(18,3),(19,2),(20,1);
explain
select col1 f1, col2 f2, col1 f3 from t2 group by f1, f2, f3;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 index NULL idx 10 NULL 20 Using index; Using temporary; Using filesort
select col1 f1, col2 f2, col1 f3 from t2 group by f1, f2, f3;
f1 f2 f3
1 20 1
2 19 2
3 18 3
4 17 4
5 16 5
6 15 6
7 14 7
8 13 8
9 12 9
10 11 10
11 10 11
12 9 12
13 8 13
14 7 14
15 6 15
16 5 16
17 4 17
18 3 18
19 2 19
20 1 20
explain
select col1 f1, col2 f2, col1 f3 from t2 order by f1, f2, f3;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 index NULL idx 10 NULL 20 Using index; Using filesort
select col1 f1, col2 f2, col1 f3 from t2 order by f1, f2, f3;
f1 f2 f3
1 20 1
2 19 2
3 18 3
4 17 4
5 16 5
6 15 6
7 14 7
8 13 8
9 12 9
10 11 10
11 10 11
12 9 12
13 8 13
14 7 14
15 6 15
16 5 16
17 4 17
18 3 18
19 2 19
20 1 20
DROP VIEW v1;
DROP TABLE t1, t2;
# End of 5.1 tests
mysql-test/t/group_by.test
View file @ 768b62fe
......@@ -1315,4 +1315,78 @@ SELECT 1 FROM t1 GROUP BY SUBSTRING(SYSDATE() FROM 'K' FOR 'jxW<');
DROP TABLE t1;
SET SQL_BIG_TABLES=0;
--echo #
--echo # MDEV-641 LP:1002108 - Wrong result (or crash) from a query with duplicated field in the group list and a limit clause
--echo # Bug#11761078: 53534: INCORRECT 'SELECT SQL_BIG_RESULT...'
--echo # WITH GROUP BY ON DUPLICATED FIELDS
--echo #
CREATE TABLE t1(
col1 int,
UNIQUE INDEX idx (col1));
INSERT INTO t1 VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10),
(11),(12),(13),(14),(15),(16),(17),(18),(19),(20);
let $query0=SELECT col1 AS field1, col1 AS field2
FROM t1 GROUP BY field1, field2;
# Needs to be range to exercise bug
--eval EXPLAIN $query0;
FLUSH STATUS;
--eval $query0;
SHOW SESSION STATUS LIKE 'Sort_scan%';
let $query=SELECT SQL_BIG_RESULT col1 AS field1, col1 AS field2
FROM t1 GROUP BY field1, field2;
# Needs to be range to exercise bug
--eval EXPLAIN $query;
FLUSH STATUS;
--eval $query;
SHOW SESSION STATUS LIKE 'Sort_scan%';
CREATE VIEW v1 AS SELECT * FROM t1;
SELECT SQL_BIG_RESULT col1 AS field1, col1 AS field2
FROM v1
GROUP BY field1, field2;
SELECT SQL_BIG_RESULT tbl1.col1 AS field1, tbl2.col1 AS field2
FROM t1 as tbl1, t1 as tbl2
GROUP BY field1, field2
LIMIT 3;
explain
select col1 f1, col1 f2 from t1 order by f2, f1;
select col1 f1, col1 f2 from t1 order by f2, f1;
explain
select col1 f1, col1 f2 from t1 group by f2 order by f2, f1;
select col1 f1, col1 f2 from t1 group by f2 order by f2, f1;
explain
select col1 f1, col1 f2 from t1 group by f1, f2 order by f2, f1;
select col1 f1, col1 f2 from t1 group by f1, f2 order by f2, f1;
CREATE TABLE t2(
col1 int,
col2 int,
UNIQUE INDEX idx (col1, col2));
INSERT INTO t2(col1, col2) VALUES
(1,20),(2,19),(3,18),(4,17),(5,16),(6,15),(7,14),(8,13),(9,12),(10,11),
(11,10),(12,9),(13,8),(14,7),(15,6),(16,5),(17,4),(18,3),(19,2),(20,1);
explain
select col1 f1, col2 f2, col1 f3 from t2 group by f1, f2, f3;
select col1 f1, col2 f2, col1 f3 from t2 group by f1, f2, f3;
explain
select col1 f1, col2 f2, col1 f3 from t2 order by f1, f2, f3;
select col1 f1, col2 f2, col1 f3 from t2 order by f1, f2, f3;
DROP VIEW v1;
DROP TABLE t1, t2;
--echo # End of 5.1 tests
sql/opt_range.cc
View file @ 768b62fe
......@@ -9481,6 +9481,13 @@ get_best_group_min_max(PARAM *param, SEL_TREE *tree)
else
goto next_index;
}
/*
This function is called on the precondition that the index is covering.
Therefore if the GROUP BY list contains more elements than the index,
these are duplicates. The GROUP BY list cannot be a prefix of the index.
*/
if (cur_part == end_part && tmp_group)
goto next_index;
}
/*
Check (GA2) if this is a DISTINCT query.
......
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