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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/>.
*
* 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.
*/
#include "mongo/db/exec/limit.h"
#include "mongo/db/exec/working_set_common.h"
#include "mongo/util/mongoutils/str.h"
namespace mongo {
// static
const char* LimitStage::kStageType = "LIMIT";
LimitStage::LimitStage(int limit, WorkingSet* ws, PlanStage* child)
: _ws(ws), _child(child), _numToReturn(limit), _commonStats(kStageType) { }
LimitStage::~LimitStage() { }
bool LimitStage::isEOF() { return (0 == _numToReturn) || _child->isEOF(); }
PlanStage::StageState LimitStage::work(WorkingSetID* out) {
++_commonStats.works;
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;
++_commonStats.advanced;
return PlanStage::ADVANCED;
}
else if (PlanStage::FAILURE == status) {
*out = id;
// If a stage fails, it may create a status WSM to indicate why it
// failed, in which case 'id' is valid. If ID is invalid, we
// create our own error message.
if (WorkingSet::INVALID_ID == id) {
mongoutils::str::stream ss;
ss << "limit stage failed to read in results from child";
Status status(ErrorCodes::InternalError, ss);
*out = WorkingSetCommon::allocateStatusMember( _ws, status);
}
return status;
}
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, InvalidationType type) {
++_commonStats.invalidates;
_child->invalidate(dl, type);
}
PlanStageStats* LimitStage::getStats() {
_commonStats.isEOF = isEOF();
_specificStats.limit = _numToReturn;
auto_ptr<PlanStageStats> ret(new PlanStageStats(_commonStats, STAGE_LIMIT));
ret->specific.reset(new LimitStats(_specificStats));
ret->children.push_back(_child->getStats());
return ret.release();
}
} // namespace mongo
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