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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/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* opCtx,
Collection* collection,
CountStageParams params,
WorkingSet* ws,
PlanStage* child)
: PlanStage(kStageType, opCtx),
_collection(collection),
_params(std::move(params)),
_leftToSkip(_params.skip),
_ws(ws) {
if (child)
_children.emplace_back(child);
}
bool CountStage::isEOF() {
if (_specificStats.recordStoreCount) {
return true;
}
if (_params.limit > 0 && _specificStats.nCounted >= _params.limit) {
return true;
}
return !_children.empty() && child()->isEOF();
}
void CountStage::recordStoreCount() {
invariant(_collection);
long long nCounted = _collection->numRecords(getOpCtx());
if (0 != _params.skip) {
nCounted -= _params.skip;
if (nCounted < 0) {
nCounted = 0;
}
}
long long limit = _params.limit;
if (limit < 0) {
limit = -limit;
}
if (limit < nCounted && 0 != limit) {
nCounted = limit;
}
_specificStats.nCounted = nCounted;
_specificStats.nSkipped = _params.skip;
_specificStats.recordStoreCount = true;
}
PlanStage::StageState CountStage::doWork(WorkingSetID* out) {
// This stage never returns a working set member.
*out = WorkingSet::INVALID_ID;
if (_params.useRecordStoreCount) {
invariant(_collection);
recordStoreCount();
return PlanStage::IS_EOF;
}
if (isEOF()) {
_commonStats.isEOF = true;
return PlanStage::IS_EOF;
}
// For cases where we can't ask the record store directly, 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::FAILURE == state || PlanStage::DEAD == state) {
// The stage which produces a failure is responsible for allocating a working set member
// with error details.
invariant(WorkingSet::INVALID_ID != id);
*out = id;
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;
return PlanStage::NEED_YIELD;
}
return PlanStage::NEED_TIME;
}
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.emplace_back(child()->getStats());
}
return ret;
}
const SpecificStats* CountStage::getSpecificStats() const {
return &_specificStats;
}
} // namespace mongo
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