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/**
* 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/>.
*/
#include "mongo/db/exec/limit.h"
namespace mongo {
LimitStage::LimitStage(int limit, WorkingSet* ws, PlanStage* child)
: _ws(ws), _child(child), _numToReturn(limit) { }
LimitStage::~LimitStage() { }
bool LimitStage::isEOF() { return (0 == _numToReturn) || _child->isEOF(); }
PlanStage::StageState LimitStage::work(WorkingSetID* out) {
++_commonStats.works;
// If we've returned as many results as we're limited to, isEOF will be true.
if (isEOF()) { return PlanStage::IS_EOF; }
WorkingSetID id;
StageState status = _child->work(&id);
if (PlanStage::ADVANCED == status) {
*out = id;
--_numToReturn;
++_commonStats.advanced;
return PlanStage::ADVANCED;
}
else {
if (PlanStage::NEED_FETCH == status) {
++_commonStats.needFetch;
}
else if (PlanStage::NEED_TIME == status) {
++_commonStats.needTime;
}
return status;
}
}
void LimitStage::prepareToYield() {
++_commonStats.yields;
_child->prepareToYield();
}
void LimitStage::recoverFromYield() {
++_commonStats.unyields;
_child->recoverFromYield();
}
void LimitStage::invalidate(const DiskLoc& dl) {
++_commonStats.invalidates;
_child->invalidate(dl);
}
PlanStageStats* LimitStage::getStats() {
_commonStats.isEOF = isEOF();
auto_ptr<PlanStageStats> ret(new PlanStageStats(_commonStats));
ret->children.push_back(_child->getStats());
return ret.release();
}
} // namespace mongo
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