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
|
/**
* Copyright (C) 2013 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects
* for all of the code used other than as permitted herein. If you modify
* file(s) with this exception, you may extend this exception to your
* version of the file(s), but you are not obligated to do so. If you do not
* wish to do so, delete this exception statement from your version. If you
* delete this exception statement from all source files in the program,
* then also delete it in the license file.
*/
#include "mongo/db/matcher/expression.h"
#pragma once
namespace mongo {
/**
* Logic for how indices can be used with an expression.
*/
class Indexability {
public:
/**
* Is an index over me->path() useful?
* This is the same thing as being sargable, if you have a RDBMS background.
*/
static bool nodeCanUseIndexOnOwnField(const MatchExpression* me) {
if (me->path().empty()) {
return false;
}
if (arrayUsesIndexOnOwnField(me)) {
return true;
}
return isIndexOnOwnFieldTypeNode(me);
}
/**
* This array operator doesn't have any children with fields and can use an index.
*
* Example: a: {$elemMatch: {$gte: 1, $lte: 1}}.
*/
static bool arrayUsesIndexOnOwnField(const MatchExpression* me) {
if (!me->isArray()) {
return false;
}
if (MatchExpression::ELEM_MATCH_VALUE != me->matchType()) {
return false;
}
// We have an ELEM_MATCH_VALUE expression. In order to be
// considered "indexable" all children of the ELEM_MATCH_VALUE
// must be "indexable" type expressions as well.
for (size_t i = 0; i < me->numChildren(); i++) {
if (!isIndexOnOwnFieldTypeNode(me->getChild(i))) {
return false;
}
}
return true;
}
/**
* Certain array operators require that the field for that operator is prepended
* to all fields in that operator's children.
*
* Example: a: {$elemMatch: {b:1, c:1}}.
*/
static bool arrayUsesIndexOnChildren(const MatchExpression* me) {
return me->isArray() && (MatchExpression::ELEM_MATCH_OBJECT == me->matchType()
|| MatchExpression::ALL == me->matchType());
}
/**
* Returns true if 'me' is a NOT, and the child of the NOT can use
* an index on its own field.
*/
static bool isBoundsGeneratingNot(const MatchExpression* me) {
return MatchExpression::NOT == me->matchType() &&
nodeCanUseIndexOnOwnField(me->getChild(0));
}
/**
* Returns true if either 'me' is a bounds generating NOT,
* or 'me' can use an index on its own field.
*/
static bool isBoundsGenerating(const MatchExpression* me) {
return isBoundsGeneratingNot(me) || nodeCanUseIndexOnOwnField(me);
}
private:
/**
* Returns true if 'me' is "sargable" but is not a negation and
* is not an array node such as ELEM_MATCH_VALUE.
*
* Used as a helper for nodeCanUseIndexOnOwnField().
*/
static bool isIndexOnOwnFieldTypeNode(const MatchExpression* me) {
return me->matchType() == MatchExpression::LTE
|| me->matchType() == MatchExpression::LT
|| me->matchType() == MatchExpression::EQ
|| me->matchType() == MatchExpression::GT
|| me->matchType() == MatchExpression::GTE
|| me->matchType() == MatchExpression::REGEX
|| me->matchType() == MatchExpression::MOD
|| me->matchType() == MatchExpression::MATCH_IN
|| me->matchType() == MatchExpression::TYPE_OPERATOR
|| me->matchType() == MatchExpression::GEO
|| me->matchType() == MatchExpression::GEO_NEAR
|| me->matchType() == MatchExpression::EXISTS
|| me->matchType() == MatchExpression::TEXT;
}
};
} // namespace mongo
|
