database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-07-30 16:24:05 +03:00
Code Activity

Bug#30665: Inconsistent optimization of IGNORE INDEX FOR {ORDER BY|GROUP BY}

Browse Source 
The optimizer takes different execution paths during EXPLAIN than SELECT,
this fix relates only to EXPLAIN, hence no behavior changes.
The test of sort keys for ORDER BY was prohibited from considering keys
that were mentioned in IGNORE KEYS FOR ORDER BY. This led to two 
inconsistencies: One was that IGNORE INDEX FOR GROUP BY and 
IGNORE INDEX FOR ORDER BY gave apparently different EXPLAINs; the latter 
erroneously claimed to do filesort. The second inconsistency 
is that the test of sort keys is called twice, finding a sort key the first
time but not the second time, leading to the mentioned filesort.

Fixed by making the test of sort keys consider all enabled 
keys on the table. This test rejects keys that are not covering, and for 
covering keys the hint should be ignored anyway.
This commit is contained in:
mhansson/martin@linux-st28.site
2007-09-28 09:36:05 +02:00
parent ed7e4b82c1
commit ab73b25d5b
5 changed files with 493 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

148
mysql-test/r/group_by.result
View File

@ -1096,7 +1096,153 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL PRIMARY 4 NULL 144 Using index; Using filesort 1 SIMPLE t1 index NULL PRIMARY 4 NULL 144 Using index; Using filesort
EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR ORDER BY (PRIMARY,i2) ORDER BY a; EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR ORDER BY (PRIMARY,i2) ORDER BY a;
id select_type table type possible_keys key key_len ref rows Extra id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL PRIMARY 4 NULL 144 Using index; Using filesort 1 SIMPLE t1 index NULL PRIMARY 4 NULL 144 Using index
SELECT a FROM t1 IGNORE INDEX FOR ORDER BY (PRIMARY,i2) ORDER BY a;
a
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR ORDER BY (PRIMARY) EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR ORDER BY (PRIMARY)
IGNORE INDEX FOR GROUP BY (i2) GROUP BY a; IGNORE INDEX FOR GROUP BY (i2) GROUP BY a;
id select_type table type possible_keys key key_len ref rows Extra id select_type table type possible_keys key key_len ref rows Extra

285
mysql-test/r/order_by.result
View File

@ -1131,3 +1131,288 @@ id c3
186 14 186 14
196 14 196 14
DROP TABLE t1,t2; DROP TABLE t1,t2;
CREATE TABLE t1 (
a INT,
b INT,
PRIMARY KEY (a),
KEY ab(a, b)
);
INSERT INTO t1 VALUES (1,1),(2,2),(3,3),(4,4);
INSERT INTO t1 SELECT a + 4, b + 4 FROM t1;
INSERT INTO t1 SELECT a + 8, b + 8 FROM t1;
INSERT INTO t1 SELECT a +16, b +16 FROM t1;
INSERT INTO t1 SELECT a +32, b +32 FROM t1;
INSERT INTO t1 SELECT a +64, b +64 FROM t1;
EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR GROUP BY (a, ab) GROUP BY a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range NULL ab 4 NULL 10 Using index for group-by
SELECT a FROM t1 IGNORE INDEX FOR GROUP BY (a, ab) GROUP BY a;
a
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
SELECT @tmp_tables_after = @tmp_tables_before ;
@tmp_tables_after = @tmp_tables_before
1
EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR ORDER BY (a, ab) ORDER BY a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL PRIMARY 4 NULL 128 Using index
SELECT a FROM t1 IGNORE INDEX FOR ORDER BY (a, ab) ORDER BY a;
a
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
SELECT @tmp_tables_after = @tmp_tables_before;
@tmp_tables_after = @tmp_tables_before
1
DROP TABLE t1;

1
mysql-test/t/group_by.test
View File

@ -811,6 +811,7 @@ EXPLAIN SELECT a FROM t1 IGNORE INDEX (PRIMARY,i2);
EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR JOIN (PRIMARY,i2); EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR JOIN (PRIMARY,i2);
EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR GROUP BY (PRIMARY,i2) GROUP BY a; EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR GROUP BY (PRIMARY,i2) GROUP BY a;
EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR ORDER BY (PRIMARY,i2) ORDER BY a; EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR ORDER BY (PRIMARY,i2) ORDER BY a;
SELECT a FROM t1 IGNORE INDEX FOR ORDER BY (PRIMARY,i2) ORDER BY a;
EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR ORDER BY (PRIMARY) EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR ORDER BY (PRIMARY)
IGNORE INDEX FOR GROUP BY (i2) GROUP BY a; IGNORE INDEX FOR GROUP BY (i2) GROUP BY a;
EXPLAIN SELECT a FROM t1 IGNORE INDEX (PRIMARY) IGNORE INDEX FOR ORDER BY (i2); EXPLAIN SELECT a FROM t1 IGNORE INDEX (PRIMARY) IGNORE INDEX FOR ORDER BY (i2);

57
mysql-test/t/order_by.test
View File

@ -779,3 +779,60 @@ EXPLAIN SELECT id,c3 FROM t2 WHERE c2 BETWEEN 20 AND 30 ORDER BY c3 LIMIT 4000;
SELECT id,c3 FROM t2 WHERE c2=11 ORDER BY c3 LIMIT 20; SELECT id,c3 FROM t2 WHERE c2=11 ORDER BY c3 LIMIT 20;
DROP TABLE t1,t2; DROP TABLE t1,t2;
#
# Bug #30665: Inconsistent optimization of IGNORE INDEX FOR {ORDER BY|GROUP BY}
#
CREATE TABLE t1 (
a INT,
b INT,
PRIMARY KEY (a),
KEY ab(a, b)
);
INSERT INTO t1 VALUES (1,1),(2,2),(3,3),(4,4);
INSERT INTO t1 SELECT a + 4, b + 4 FROM t1;
INSERT INTO t1 SELECT a + 8, b + 8 FROM t1;
INSERT INTO t1 SELECT a +16, b +16 FROM t1;
INSERT INTO t1 SELECT a +32, b +32 FROM t1;
INSERT INTO t1 SELECT a +64, b +64 FROM t1;
EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR GROUP BY (a, ab) GROUP BY a;
--disable_query_log
--let $q = `show status like 'Created_tmp_tables';`
eval set @tmp_tables_before =
CAST(REPLACE('$q', 'Created_tmp_tables', '') AS UNSIGNED);
--enable_query_log
SELECT a FROM t1 IGNORE INDEX FOR GROUP BY (a, ab) GROUP BY a;
# this query creates one temporary table in itself, which we are not
# interested in.
--disable_query_log
--let $q = `show status like 'Created_tmp_tables';`
eval set @tmp_tables_after =
CAST(REPLACE('$q', 'Created_tmp_tables', '') AS UNSIGNED);
--enable_query_log
SELECT @tmp_tables_after = @tmp_tables_before ;
EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR ORDER BY (a, ab) ORDER BY a;
--disable_query_log
--let $q = `show status like 'Created_tmp_tables';`
eval set @tmp_tables_before =
CAST(REPLACE('$q', 'Created_tmp_tables', '') AS UNSIGNED);
--enable_query_log
SELECT a FROM t1 IGNORE INDEX FOR ORDER BY (a, ab) ORDER BY a;
--disable_query_log
--let $q = `show status like 'Created_tmp_tables';`
eval set @tmp_tables_after =
CAST(REPLACE('$q', 'Created_tmp_tables', '') AS UNSIGNED);
--enable_query_log
SELECT @tmp_tables_after = @tmp_tables_before;
DROP TABLE t1;

4
sql/sql_select.cc
View File

@ -1695,7 +1695,7 @@ JOIN::exec()
test_if_skip_sort_order(&join_tab[const_tables], order, test_if_skip_sort_order(&join_tab[const_tables], order,
select_limit, 0, select_limit, 0,
&join_tab[const_tables].table-> &join_tab[const_tables].table->
keys_in_use_for_order_by)))) keys_in_use_for_query))))
order=0; order=0;
having= tmp_having; having= tmp_having;
select_describe(this, need_tmp, select_describe(this, need_tmp,
@ -12614,6 +12614,8 @@ find_field_in_item_list (Field *field, void *data)
If we can use an index, the JOIN_TAB / tab->select struct If we can use an index, the JOIN_TAB / tab->select struct
is changed to use the index. is changed to use the index.
The index must cover all fields in <order>, or it will not be considered.
Return: Return:
0 We have to use filesort to do the sorting 0 We have to use filesort to do the sorting
1 We can use an index. 1 We can use an index.