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
184
|
/**
* 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/platform/basic.h"
#include "mongo/db/exec/count.h"
#include "mongo/db/catalog/collection.h"
#include "mongo/db/exec/scoped_timer.h"
#include "mongo/db/exec/working_set_common.h"
#include "mongo/stdx/memory.h"
namespace mongo {
using std::unique_ptr;
using std::vector;
using stdx::make_unique;
// static
const char* CountStage::kStageType = "COUNT";
CountStage::CountStage(OperationContext* txn,
Collection* collection,
const CountRequest& request,
WorkingSet* ws,
PlanStage* child)
: PlanStage(kStageType),
_txn(txn),
_collection(collection),
_request(request),
_leftToSkip(request.getSkip()),
_ws(ws) {
if (child)
_children.emplace_back(child);
}
bool CountStage::isEOF() {
if (_specificStats.trivialCount) {
return true;
}
if (_request.getLimit() > 0 && _specificStats.nCounted >= _request.getLimit()) {
return true;
}
return !_children.empty() && child()->isEOF();
}
void CountStage::trivialCount() {
invariant(_collection);
long long nCounted = _collection->numRecords(_txn);
if (0 != _request.getSkip()) {
nCounted -= _request.getSkip();
if (nCounted < 0) {
nCounted = 0;
}
}
long long limit = _request.getLimit();
if (limit < 0) {
limit = -limit;
}
if (limit < nCounted && 0 != limit) {
nCounted = limit;
}
_specificStats.nCounted = nCounted;
_specificStats.nSkipped = _request.getSkip();
_specificStats.trivialCount = true;
}
PlanStage::StageState CountStage::work(WorkingSetID* out) {
++_commonStats.works;
// Adds the amount of time taken by work() to executionTimeMillis.
ScopedTimer timer(&_commonStats.executionTimeMillis);
// This stage never returns a working set member.
*out = WorkingSet::INVALID_ID;
// If we don't have a query and we have a non-NULL collection, then we can execute this
// as a trivial count (just ask the collection for how many records it has).
if (_request.getQuery().isEmpty() && NULL != _collection) {
trivialCount();
return PlanStage::IS_EOF;
}
if (isEOF()) {
_commonStats.isEOF = true;
return PlanStage::IS_EOF;
}
// For non-trivial counts, we should always have a child stage from which we can retrieve
// results.
invariant(child());
WorkingSetID id = WorkingSet::INVALID_ID;
PlanStage::StageState state = child()->work(&id);
if (PlanStage::IS_EOF == state) {
_commonStats.isEOF = true;
return PlanStage::IS_EOF;
} else if (PlanStage::DEAD == state) {
return state;
} else if (PlanStage::FAILURE == state || PlanStage::DEAD == state) {
*out = id;
// If a stage fails, it may create a status WSM to indicate why it failed, in which
// case 'id' is valid. If ID is invalid, we create our own error message.
if (WorkingSet::INVALID_ID == id) {
const std::string errmsg = "count stage failed to read result from child";
Status status = Status(ErrorCodes::InternalError, errmsg);
*out = WorkingSetCommon::allocateStatusMember(_ws, status);
}
return state;
} else if (PlanStage::ADVANCED == state) {
// We got a result. If we're still skipping, then decrement the number left to skip.
// Otherwise increment the count until we hit the limit.
if (_leftToSkip > 0) {
_leftToSkip--;
_specificStats.nSkipped++;
} else {
_specificStats.nCounted++;
}
// Count doesn't need the actual results, so we just discard any valid working
// set members that got returned from the child.
if (WorkingSet::INVALID_ID != id) {
_ws->free(id);
}
} else if (PlanStage::NEED_YIELD == state) {
*out = id;
_commonStats.needYield++;
return PlanStage::NEED_YIELD;
}
_commonStats.needTime++;
return PlanStage::NEED_TIME;
}
void CountStage::doRestoreState(OperationContext* opCtx) {
_txn = opCtx;
}
unique_ptr<PlanStageStats> CountStage::getStats() {
_commonStats.isEOF = isEOF();
unique_ptr<PlanStageStats> ret = make_unique<PlanStageStats>(_commonStats, STAGE_COUNT);
ret->specific = make_unique<CountStats>(_specificStats);
if (!_children.empty()) {
ret->children.push_back(child()->getStats().release());
}
return ret;
}
const SpecificStats* CountStage::getSpecificStats() const {
return &_specificStats;
}
} // namespace mongo
|
