summaryrefslogtreecommitdiff
path: root/src/mongo/db/exec/index_scan.cpp
blob: 767539e65b42465b0f97d0712fcebe9b9ca2809c (plain)
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
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
/**
 *    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.
 */

#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kQuery

#include "mongo/platform/basic.h"

#include "mongo/db/exec/index_scan.h"

#include "mongo/db/concurrency/write_conflict_exception.h"
#include "mongo/db/exec/filter.h"
#include "mongo/db/exec/scoped_timer.h"
#include "mongo/db/exec/working_set_computed_data.h"
#include "mongo/db/index/index_access_method.h"
#include "mongo/db/index/index_descriptor.h"
#include "mongo/db/query/index_bounds_builder.h"
#include "mongo/stdx/memory.h"
#include "mongo/util/log.h"

namespace {

// Return a value in the set {-1, 0, 1} to represent the sign of parameter i.
int sgn(int i) {
    if (i == 0)
        return 0;
    return i > 0 ? 1 : -1;
}

}  // namespace

namespace mongo {

// static
const char* IndexScan::kStageType = "IXSCAN";

IndexScan::IndexScan(OperationContext* txn,
                     const IndexScanParams& params,
                     WorkingSet* workingSet,
                     const MatchExpression* filter)
    : PlanStage(kStageType, txn),
      _workingSet(workingSet),
      _iam(params.descriptor->getIndexCatalog()->getIndex(params.descriptor)),
      _keyPattern(params.descriptor->keyPattern().getOwned()),
      _scanState(INITIALIZING),
      _filter(filter),
      _shouldDedup(true),
      _forward(params.direction == 1),
      _params(params),
      _startKeyInclusive(IndexBounds::isStartIncludedInBound(params.bounds.boundInclusion)),
      _endKeyInclusive(IndexBounds::isEndIncludedInBound(params.bounds.boundInclusion)) {
    // We can't always access the descriptor in the call to getStats() so we pull
    // any info we need for stats reporting out here.
    _specificStats.keyPattern = _keyPattern;
    if (BSONElement collationElement = _params.descriptor->getInfoElement("collation")) {
        invariant(collationElement.isABSONObj());
        _specificStats.collation = collationElement.Obj().getOwned();
    }
    _specificStats.indexName = _params.descriptor->indexName();
    _specificStats.isMultiKey = _params.descriptor->isMultikey(getOpCtx());
    _specificStats.multiKeyPaths = _params.descriptor->getMultikeyPaths(getOpCtx());
    _specificStats.isUnique = _params.descriptor->unique();
    _specificStats.isSparse = _params.descriptor->isSparse();
    _specificStats.isPartial = _params.descriptor->isPartial();
    _specificStats.indexVersion = static_cast<int>(_params.descriptor->version());
}

boost::optional<IndexKeyEntry> IndexScan::initIndexScan() {
    if (_params.doNotDedup) {
        _shouldDedup = false;
    } else {
        // TODO it is incorrect to rely on this not changing. SERVER-17678
        _shouldDedup = _params.descriptor->isMultikey(getOpCtx());
    }

    // Perform the possibly heavy-duty initialization of the underlying index cursor.
    _indexCursor = _iam->newCursor(getOpCtx(), _forward);

    // We always seek once to establish the cursor position.
    ++_specificStats.seeks;

    if (_params.bounds.isSimpleRange) {
        // Start at one key, end at another.
        _startKey = _params.bounds.startKey;
        _endKey = _params.bounds.endKey;
        _indexCursor->setEndPosition(_endKey, _endKeyInclusive);
        return _indexCursor->seek(_startKey, _startKeyInclusive);
    } else {
        // For single intervals, we can use an optimized scan which checks against the position
        // of an end cursor.  For all other index scans, we fall back on using
        // IndexBoundsChecker to determine when we've finished the scan.
        if (IndexBoundsBuilder::isSingleInterval(
                _params.bounds, &_startKey, &_startKeyInclusive, &_endKey, &_endKeyInclusive)) {
            _indexCursor->setEndPosition(_endKey, _endKeyInclusive);
            return _indexCursor->seek(_startKey, _startKeyInclusive);
        } else {
            _checker.reset(new IndexBoundsChecker(&_params.bounds, _keyPattern, _params.direction));

            if (!_checker->getStartSeekPoint(&_seekPoint))
                return boost::none;

            return _indexCursor->seek(_seekPoint);
        }
    }
}

PlanStage::StageState IndexScan::doWork(WorkingSetID* out) {
    // Get the next kv pair from the index, if any.
    boost::optional<IndexKeyEntry> kv;
    try {
        switch (_scanState) {
            case INITIALIZING:
                kv = initIndexScan();
                break;
            case GETTING_NEXT:
                kv = _indexCursor->next();
                break;
            case NEED_SEEK:
                ++_specificStats.seeks;
                kv = _indexCursor->seek(_seekPoint);
                break;
            case HIT_END:
                return PlanStage::IS_EOF;
        }
    } catch (const WriteConflictException& wce) {
        *out = WorkingSet::INVALID_ID;
        return PlanStage::NEED_YIELD;
    }

    if (kv) {
        // In debug mode, check that the cursor isn't lying to us.
        if (kDebugBuild && !_startKey.isEmpty()) {
            int cmp = kv->key.woCompare(_startKey,
                                        Ordering::make(_params.descriptor->keyPattern()),
                                        /*compareFieldNames*/ false);
            if (cmp == 0)
                dassert(_startKeyInclusive);
            dassert(_forward ? cmp >= 0 : cmp <= 0);
        }

        if (kDebugBuild && !_endKey.isEmpty()) {
            int cmp = kv->key.woCompare(_endKey,
                                        Ordering::make(_params.descriptor->keyPattern()),
                                        /*compareFieldNames*/ false);
            if (cmp == 0)
                dassert(_endKeyInclusive);
            dassert(_forward ? cmp <= 0 : cmp >= 0);
        }

        ++_specificStats.keysExamined;
        if (_params.maxScan && _specificStats.keysExamined >= _params.maxScan) {
            kv = boost::none;
        }
    }

    if (kv && _checker) {
        switch (_checker->checkKey(kv->key, &_seekPoint)) {
            case IndexBoundsChecker::VALID:
                break;

            case IndexBoundsChecker::DONE:
                kv = boost::none;
                break;

            case IndexBoundsChecker::MUST_ADVANCE:
                _scanState = NEED_SEEK;
                return PlanStage::NEED_TIME;
        }
    }

    if (!kv) {
        _scanState = HIT_END;
        _commonStats.isEOF = true;
        _indexCursor.reset();
        return PlanStage::IS_EOF;
    }

    _scanState = GETTING_NEXT;

    if (_shouldDedup) {
        ++_specificStats.dupsTested;
        if (!_returned.insert(kv->loc).second) {
            // We've seen this RecordId before. Skip it this time.
            ++_specificStats.dupsDropped;
            return PlanStage::NEED_TIME;
        }
    }

    if (_filter) {
        if (!Filter::passes(kv->key, _keyPattern, _filter)) {
            return PlanStage::NEED_TIME;
        }
    }

    if (!kv->key.isOwned())
        kv->key = kv->key.getOwned();

    // We found something to return, so fill out the WSM.
    WorkingSetID id = _workingSet->allocate();
    WorkingSetMember* member = _workingSet->get(id);
    member->recordId = kv->loc;
    member->keyData.push_back(IndexKeyDatum(_keyPattern, kv->key, _iam));
    _workingSet->transitionToRecordIdAndIdx(id);

    if (_params.addKeyMetadata) {
        BSONObjBuilder bob;
        bob.appendKeys(_keyPattern, kv->key);
        member->addComputed(new IndexKeyComputedData(bob.obj()));
    }

    *out = id;
    return PlanStage::ADVANCED;
}

bool IndexScan::isEOF() {
    return _commonStats.isEOF;
}

void IndexScan::doSaveState() {
    if (!_indexCursor)
        return;

    if (_scanState == NEED_SEEK) {
        _indexCursor->saveUnpositioned();
        return;
    }

    _indexCursor->save();
}

void IndexScan::doRestoreState() {
    if (_indexCursor)
        _indexCursor->restore();
}

void IndexScan::doDetachFromOperationContext() {
    if (_indexCursor)
        _indexCursor->detachFromOperationContext();
}

void IndexScan::doReattachToOperationContext() {
    if (_indexCursor)
        _indexCursor->reattachToOperationContext(getOpCtx());
}

void IndexScan::doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) {
    // The only state we're responsible for holding is what RecordIds to drop.  If a document
    // mutates the underlying index cursor will deal with it.
    if (INVALIDATION_MUTATION == type) {
        return;
    }

    // If we see this RecordId again, it may not be the same document it was before, so we want
    // to return it if we see it again.
    unordered_set<RecordId, RecordId::Hasher>::iterator it = _returned.find(dl);
    if (it != _returned.end()) {
        ++_specificStats.seenInvalidated;
        _returned.erase(it);
    }
}

std::unique_ptr<PlanStageStats> IndexScan::getStats() {
    // WARNING: this could be called even if the collection was dropped.  Do not access any
    // catalog information here.

    // Add a BSON representation of the filter to the stats tree, if there is one.
    if (NULL != _filter) {
        BSONObjBuilder bob;
        _filter->serialize(&bob);
        _commonStats.filter = bob.obj();
    }

    // These specific stats fields never change.
    if (_specificStats.indexType.empty()) {
        _specificStats.indexType = "BtreeCursor";  // TODO amName;

        _specificStats.indexBounds = _params.bounds.toBSON();

        _specificStats.direction = _params.direction;
    }

    std::unique_ptr<PlanStageStats> ret =
        stdx::make_unique<PlanStageStats>(_commonStats, STAGE_IXSCAN);
    ret->specific = stdx::make_unique<IndexScanStats>(_specificStats);
    return ret;
}

const SpecificStats* IndexScan::getSpecificStats() const {
    return &_specificStats;
}

}  // namespace mongo