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
145
146
147
148
149
150
151
152
153
154
155
156
157
158
|
/**
* 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.
*/
#pragma once
#include "mongo/db/diskloc.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/exec/projection_exec.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/matcher/expression.h"
namespace mongo {
struct ProjectionStageParams {
enum ProjectionImplementation {
// The default case. Will handle every projection.
NO_FAST_PATH,
// The projection is simple inclusion and is totally covered by one index.
COVERED_ONE_INDEX,
// The projection is simple inclusion and we expect an object.
SIMPLE_DOC
};
ProjectionStageParams(const MatchExpressionParser::WhereCallback& wc)
: projImpl(NO_FAST_PATH), fullExpression(NULL), whereCallback(&wc) { }
ProjectionImplementation projImpl;
// The projection object. We lack a ProjectionExpression or similar so we use a BSONObj.
BSONObj projObj;
// If we have a positional or elemMatch projection we need a MatchExpression to pull out the
// right data.
// Not owned here, we do not take ownership.
const MatchExpression* fullExpression;
// If (COVERED_ONE_INDEX == projObj) this is the key pattern we're extracting covered data
// from. Otherwise, this field is ignored.
BSONObj coveredKeyObj;
// Used for creating context for the $where clause processing. Not owned.
const MatchExpressionParser::WhereCallback* whereCallback;
};
/**
* This stage computes a projection.
*/
class ProjectionStage : public PlanStage {
public:
ProjectionStage(const ProjectionStageParams& params,
WorkingSet* ws,
PlanStage* child);
virtual ~ProjectionStage();
virtual bool isEOF();
virtual StageState work(WorkingSetID* out);
virtual void saveState();
virtual void restoreState(OperationContext* opCtx);
virtual void invalidate(const DiskLoc& dl, InvalidationType type);
virtual std::vector<PlanStage*> getChildren() const;
virtual StageType stageType() const { return STAGE_PROJECTION; }
PlanStageStats* getStats();
virtual const CommonStats* getCommonStats();
virtual const SpecificStats* getSpecificStats();
typedef unordered_set<StringData, StringData::Hasher> FieldSet;
/**
* Given the projection spec for a simple inclusion projection,
* 'projObj', populates 'includedFields' with the set of field
* names to be included.
*/
static void getSimpleInclusionFields(const BSONObj& projObj,
FieldSet* includedFields);
/**
* Applies a simple inclusion projection to 'in', including
* only the fields specified by 'includedFields'.
*
* The resulting document is constructed using 'bob'.
*/
static void transformSimpleInclusion(const BSONObj& in,
const FieldSet& includedFields,
BSONObjBuilder& bob);
static const char* kStageType;
private:
Status transform(WorkingSetMember* member);
scoped_ptr<ProjectionExec> _exec;
// _ws is not owned by us.
WorkingSet* _ws;
scoped_ptr<PlanStage> _child;
// Stats
CommonStats _commonStats;
ProjectionStats _specificStats;
// Fast paths:
ProjectionStageParams::ProjectionImplementation _projImpl;
// Used by all projection implementations.
BSONObj _projObj;
// Data used for both SIMPLE_DOC and COVERED_ONE_INDEX paths.
// Has the field names present in the simple projection.
unordered_set<StringData, StringData::Hasher> _includedFields;
//
// Used for the COVERED_ONE_INDEX path.
//
BSONObj _coveredKeyObj;
// Field names can be empty in 2.4 and before so we can't use them as a sentinel value.
// If the i-th entry is true we include the i-th field in the key.
std::vector<bool> _includeKey;
// If the i-th entry of _includeKey is true this is the field name for the i-th key field.
std::vector<StringData> _keyFieldNames;
};
} // namespace mongo
|
