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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/limit.h"
#include "mongo/db/exec/scoped_timer.h"
#include "mongo/db/exec/working_set_common.h"
#include "mongo/stdx/memory.h"
#include "mongo/util/mongoutils/str.h"
namespace mongo {
using std::unique_ptr;
using std::vector;
using stdx::make_unique;
// static
const char* LimitStage::kStageType = "LIMIT";
LimitStage::LimitStage(OperationContext* opCtx, long long limit, WorkingSet* ws, PlanStage* child)
: PlanStage(kStageType, opCtx), _ws(ws), _numToReturn(limit) {
_specificStats.limit = _numToReturn;
_children.emplace_back(child);
}
LimitStage::~LimitStage() {}
bool LimitStage::isEOF() {
return (0 == _numToReturn) || child()->isEOF();
}
PlanStage::StageState LimitStage::doWork(WorkingSetID* out) {
if (0 == _numToReturn) {
// We've returned as many results as we're limited to.
return PlanStage::IS_EOF;
}
WorkingSetID id = WorkingSet::INVALID_ID;
StageState status = child()->work(&id);
if (PlanStage::ADVANCED == status) {
*out = id;
--_numToReturn;
} else if (PlanStage::FAILURE == status) {
// The stage which produces a failure is responsible for allocating a working set member
// with error details.
invariant(WorkingSet::INVALID_ID != id);
*out = id;
} else if (PlanStage::NEED_YIELD == status) {
*out = id;
}
return status;
}
unique_ptr<PlanStageStats> LimitStage::getStats() {
_commonStats.isEOF = isEOF();
unique_ptr<PlanStageStats> ret = make_unique<PlanStageStats>(_commonStats, STAGE_LIMIT);
ret->specific = make_unique<LimitStats>(_specificStats);
ret->children.emplace_back(child()->getStats());
return ret;
}
const SpecificStats* LimitStage::getSpecificStats() const {
return &_specificStats;
}
} // namespace mongo
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