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/**
* Copyright (C) 2015 MongoDB 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.
*/
#pragma once
#include <memory>
#include "mongo/bson/bsonobj.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/index/btree_key_generator.h"
#include "mongo/db/query/index_bounds.h"
#include "mongo/db/query/stage_types.h"
namespace mongo {
class Collection;
class WorkingSetMember;
/**
* Maps a WSM value to a BSONObj key that can then be sorted via BSONObjCmp.
*/
class SortKeyGenerator {
public:
/**
* 'sortSpec' is the BSONObj in the .sort(...) clause.
*
* 'queryObj' is the BSONObj in the .find(...) clause. For multikey arrays we have to
* ensure that the value we select to sort by is within bounds generated by
* executing 'queryObj' using the virtual index with key pattern 'sortSpec'.
*
* 'txn' must point to a valid OperationContext, but 'txn' does not need to outlive the
* constructed SortKeyGenerator.
*/
SortKeyGenerator(OperationContext* txn, const BSONObj& sortSpec, const BSONObj& queryObj);
/**
* Returns the key used to sort 'member'. If the member is in LOC_AND_IDX state, it must not
* contain a $meta textScore in its sort spec, and this function will use the index key data
* stored in 'member' to extract the sort key. Otherwise, if the member is in LOC_AND_OBJ or
* OWNED_OBJ state, this function will use the object data stored in 'member' to extract the
* sort key.
*/
Status getSortKey(const WorkingSetMember& member, BSONObj* objOut) const;
private:
StatusWith<BSONObj> getSortKeyFromIndexKey(const WorkingSetMember& member) const;
StatusWith<BSONObj> getSortKeyFromObject(const WorkingSetMember& member) const;
/**
* In order to emulate the existing sort behavior we must make unindexed sort behavior as
* consistent as possible with indexed sort behavior. As such, we must only consider index
* keys that we would encounter if we were answering the query using the sort-providing
* index.
*
* Populates _hasBounds and _bounds.
*/
void getBoundsForSort(OperationContext* txn, const BSONObj& queryObj, const BSONObj& sortObj);
// The raw object in .sort()
BSONObj _rawSortSpec;
// The sort pattern with any non-Btree sort pulled out.
BSONObj _btreeObj;
// If we're not sorting with a $meta value we can short-cut some work.
bool _sortHasMeta;
// True if the bounds are valid.
bool _hasBounds;
// The bounds generated from the query we're sorting.
IndexBounds _bounds;
// Helper to extract sorting keys from documents.
std::unique_ptr<BtreeKeyGenerator> _keyGen;
// Helper to filter keys, ensuring keys generated with _keyGen are within _bounds.
std::unique_ptr<IndexBoundsChecker> _boundsChecker;
};
/**
* Passes results from the child through after adding the sort key for each result as
* WorkingSetMember computed data.
*/
class SortKeyGeneratorStage final : public PlanStage {
public:
SortKeyGeneratorStage(OperationContext* opCtx,
PlanStage* child,
WorkingSet* ws,
const BSONObj& sortSpecObj,
const BSONObj& queryObj);
bool isEOF() final;
StageState doWork(WorkingSetID* out) final;
StageType stageType() const final {
return STAGE_SORT_KEY_GENERATOR;
}
std::unique_ptr<PlanStageStats> getStats() final;
const SpecificStats* getSpecificStats() const final;
static const char* kStageType;
private:
WorkingSet* const _ws;
// The raw sort pattern as expressed by the user.
const BSONObj _sortSpec;
// The raw query as expressed by the user.
const BSONObj _query;
std::unique_ptr<SortKeyGenerator> _sortKeyGen;
};
} // namespace mongo
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