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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* 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
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* 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 Server Side 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/exec/count_scan.h"
#include <memory>
#include "mongo/db/catalog/index_catalog.h"
#include "mongo/db/concurrency/write_conflict_exception.h"
#include "mongo/db/exec/scoped_timer.h"
#include "mongo/db/index/index_access_method.h"
namespace mongo {
namespace {
/**
* This function replaces field names in *replace* with those from the object
* *fieldNames*, preserving field ordering. Both objects must have the same
* number of fields.
*
* Example:
*
* replaceBSONKeyNames({ 'a': 1, 'b' : 1 }, { '': 'foo', '', 'bar' }) =>
*
* { 'a' : 'foo' }, { 'b' : 'bar' }
*/
BSONObj replaceBSONFieldNames(const BSONObj& replace, const BSONObj& fieldNames) {
invariant(replace.nFields() == fieldNames.nFields());
BSONObjBuilder bob;
auto iter = fieldNames.begin();
for (const BSONElement& el : replace) {
bob.appendAs(el, (*iter++).fieldNameStringData());
}
return bob.obj();
}
}
using std::unique_ptr;
using std::vector;
// static
const char* CountScan::kStageType = "COUNT_SCAN";
// When building the CountScan stage we take the keyPattern, index name, and multikey details from
// the CountScanParams rather than resolving them via the IndexDescriptor, since these may differ
// from the descriptor's contents.
CountScan::CountScan(OperationContext* opCtx, CountScanParams params, WorkingSet* workingSet)
: RequiresIndexStage(kStageType, opCtx, params.indexDescriptor),
_workingSet(workingSet),
_keyPattern(std::move(params.keyPattern)),
_shouldDedup(params.isMultiKey),
_startKey(std::move(params.startKey)),
_startKeyInclusive(params.startKeyInclusive),
_endKey(std::move(params.endKey)),
_endKeyInclusive(params.endKeyInclusive) {
_specificStats.indexName = params.name;
_specificStats.keyPattern = _keyPattern;
_specificStats.isMultiKey = params.isMultiKey;
_specificStats.multiKeyPaths = params.multikeyPaths;
_specificStats.isUnique = params.indexDescriptor->unique();
_specificStats.isSparse = params.indexDescriptor->isSparse();
_specificStats.isPartial = params.indexDescriptor->isPartial();
_specificStats.indexVersion = static_cast<int>(params.indexDescriptor->version());
_specificStats.collation = params.indexDescriptor->infoObj()
.getObjectField(IndexDescriptor::kCollationFieldName)
.getOwned();
// endKey must be after startKey in index order since we only do forward scans.
dassert(_startKey.woCompare(_endKey,
Ordering::make(_keyPattern),
/*compareFieldNames*/ false) <= 0);
}
PlanStage::StageState CountScan::doWork(WorkingSetID* out) {
if (_commonStats.isEOF)
return PlanStage::IS_EOF;
boost::optional<IndexKeyEntry> entry;
const bool needInit = !_cursor;
try {
// We don't care about the keys.
const auto kWantLoc = SortedDataInterface::Cursor::kWantLoc;
if (needInit) {
// First call to work(). Perform cursor init.
_cursor = indexAccessMethod()->newCursor(getOpCtx());
_cursor->setEndPosition(_endKey, _endKeyInclusive);
entry = _cursor->seek(_startKey, _startKeyInclusive, kWantLoc);
} else {
entry = _cursor->next(kWantLoc);
}
} catch (const WriteConflictException&) {
if (needInit) {
// Release our cursor and try again next time.
_cursor.reset();
}
*out = WorkingSet::INVALID_ID;
return PlanStage::NEED_YIELD;
}
++_specificStats.keysExamined;
if (!entry) {
_commonStats.isEOF = true;
_cursor.reset();
return PlanStage::IS_EOF;
}
if (_shouldDedup && !_returned.insert(entry->loc).second) {
// *loc was already in _returned.
return PlanStage::NEED_TIME;
}
WorkingSetID id = _workingSet->allocate();
_workingSet->transitionToRecordIdAndObj(id);
*out = id;
return PlanStage::ADVANCED;
}
bool CountScan::isEOF() {
return _commonStats.isEOF;
}
void CountScan::doSaveStateRequiresIndex() {
if (_cursor)
_cursor->save();
}
void CountScan::doRestoreStateRequiresIndex() {
if (_cursor)
_cursor->restore();
}
void CountScan::doDetachFromOperationContext() {
if (_cursor)
_cursor->detachFromOperationContext();
}
void CountScan::doReattachToOperationContext() {
if (_cursor)
_cursor->reattachToOperationContext(getOpCtx());
}
unique_ptr<PlanStageStats> CountScan::getStats() {
unique_ptr<PlanStageStats> ret =
std::make_unique<PlanStageStats>(_commonStats, STAGE_COUNT_SCAN);
unique_ptr<CountScanStats> countStats = std::make_unique<CountScanStats>(_specificStats);
countStats->keyPattern = _specificStats.keyPattern.getOwned();
countStats->startKey = replaceBSONFieldNames(_startKey, countStats->keyPattern);
countStats->startKeyInclusive = _startKeyInclusive;
countStats->endKey = replaceBSONFieldNames(_endKey, countStats->keyPattern);
countStats->endKeyInclusive = _endKeyInclusive;
ret->specific = std::move(countStats);
return ret;
}
const SpecificStats* CountScan::getSpecificStats() const {
return &_specificStats;
}
} // namespace mongo
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