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
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
|
/**
* Copyright (C) 2013-2014 MongoDB 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/exec/plan_stage.h"
#include "mongo/db/index/index_access_method.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/matcher/expression.h"
#include "mongo/db/query/index_bounds.h"
#include "mongo/db/record_id.h"
#include "mongo/db/storage/index_entry_comparison.h"
#include "mongo/db/storage/sorted_data_interface.h"
#include "mongo/platform/unordered_set.h"
namespace mongo {
class IndexAccessMethod;
class IndexDescriptor;
class WorkingSet;
struct IndexScanParams {
IndexScanParams()
: descriptor(NULL), direction(1), doNotDedup(false), maxScan(0), addKeyMetadata(false) {}
const IndexDescriptor* descriptor;
IndexBounds bounds;
int direction;
bool doNotDedup;
// How many keys will we look at?
size_t maxScan;
// Do we want to add the key as metadata?
bool addKeyMetadata;
};
/**
* Stage scans over an index from startKey to endKey, returning results that pass the provided
* filter. Internally dedups on RecordId.
*
* Sub-stage preconditions: None. Is a leaf and consumes no stage data.
*/
class IndexScan : public PlanStage {
public:
/**
* Keeps track of what this index scan is currently doing so that it
* can do the right thing on the next call to work().
*/
enum ScanState {
// Need to initialize the underlying index traversal machinery.
INITIALIZING,
// Skipping keys as directed by the _checker.
NEED_SEEK,
// Retrieving the next key, and applying the filter if necessary.
GETTING_NEXT,
// The index scan is finished.
HIT_END
};
IndexScan(OperationContext* txn,
const IndexScanParams& params,
WorkingSet* workingSet,
const MatchExpression* filter);
virtual ~IndexScan() {}
virtual StageState work(WorkingSetID* out);
virtual bool isEOF();
virtual void saveState();
virtual void restoreState(OperationContext* opCtx);
virtual void invalidate(OperationContext* txn, const RecordId& dl, InvalidationType type);
virtual std::vector<PlanStage*> getChildren() const;
virtual StageType stageType() const {
return STAGE_IXSCAN;
}
virtual PlanStageStats* getStats();
virtual const CommonStats* getCommonStats() const;
virtual const SpecificStats* getSpecificStats() const;
static const char* kStageType;
private:
/**
* Initialize the underlying index Cursor, returning first result if any.
*/
boost::optional<IndexKeyEntry> initIndexScan();
// transactional context for read locks. Not owned by us
OperationContext* _txn;
// The WorkingSet we fill with results. Not owned by us.
WorkingSet* const _workingSet;
// Index access.
const IndexAccessMethod* const _iam; // owned by Collection -> IndexCatalog
std::unique_ptr<SortedDataInterface::Cursor> _indexCursor;
const BSONObj _keyPattern;
// Keeps track of what work we need to do next.
ScanState _scanState;
// Contains expressions only over fields in the index key. We assume this is built
// correctly by whomever creates this class.
// The filter is not owned by us.
const MatchExpression* const _filter;
// Could our index have duplicates? If so, we use _returned to dedup.
bool _shouldDedup;
unordered_set<RecordId, RecordId::Hasher> _returned;
const bool _forward;
const IndexScanParams _params;
// Stats
CommonStats _commonStats;
IndexScanStats _specificStats;
//
// This class employs one of two different algorithms for determining when the index scan
// has reached the end:
//
//
// 1) If the index scan is not a single contiguous interval, then we use an
// IndexBoundsChecker to determine which keys to return and when to stop scanning.
// In this case, _checker will be non-NULL.
//
std::unique_ptr<IndexBoundsChecker> _checker;
IndexSeekPoint _seekPoint;
//
// 2) If the index scan is a single contiguous interval, then the scan can execute faster by
// letting the index cursor tell us when it hits the end, rather than repeatedly doing
// BSON compares against scanned keys. In this case _checker will be NULL.
//
// The key that the index cursor should stop on/after.
BSONObj _endKey;
// Is the end key included in the range?
bool _endKeyInclusive;
};
} // namespace mongo
|
