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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.
*/
#pragma once
#include <set>
#include <vector>
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/exec/sort_executor.h"
#include "mongo/db/exec/sort_key_comparator.h"
#include "mongo/db/exec/sort_key_generator.h"
#include "mongo/db/exec/working_set.h"
#include "mongo/db/record_id.h"
namespace mongo {
/**
* Sorts the input received from the child according to the sort pattern provided. If
* 'addSortKeyMetadata' is true, then also attaches the sort key as metadata. This could be consumed
* downstream for a sort-merge on a merging node, or by a $meta:"sortKey" expression.
*
* Concrete implementations derive from this abstract base class by implementing methods for
* spooling and unspooling.
*/
class SortStage : public PlanStage {
public:
static constexpr StringData kStageType = "SORT"_sd;
SortStage(boost::intrusive_ptr<ExpressionContext> expCtx,
WorkingSet* ws,
SortPattern sortPattern,
bool addSortKeyMetadata,
std::unique_ptr<PlanStage> child);
/**
* Loads the WorkingSetMember pointed to by 'wsid' into the set of objects being sorted. This
* should be called repeatedly until all documents are loaded, followed by a single call to
* 'loadingDone()'. Illegal to call after 'loadingDone()' has been called.
*/
virtual void spool(WorkingSetID wsid) = 0;
/**
* Indicates that all documents to be sorted have been loaded via 'spool()'. This method must
* not be called more than once.
*/
virtual void loadingDone() = 0;
/**
* Returns an id referring to the next WorkingSetMember in the sorted stream of results.
*
* If there is another WSM, the id is returned via the out-parameter and the return value is
* PlanStage::ADVANCED. If there are no more documents remaining in the sorted stream, returns
* PlanStage::IS_EOF, and 'out' is left unmodified.
*
* Illegal to call before 'loadingDone()' has been called.
*/
virtual StageState unspool(WorkingSetID* out) = 0;
StageState doWork(WorkingSetID* out) final;
std::unique_ptr<PlanStageStats> getStats() override final;
protected:
// Not owned by us.
WorkingSet* _ws;
const SortKeyGenerator _sortKeyGen;
const bool _addSortKeyMetadata;
private:
// Whether or not we have finished loading data into '_sortExecutor'.
bool _populated = false;
};
/**
* Generic sorting implementation which can handle sorting any WorkingSetMember, including those
* that have RecordIds, metadata, or which represent index keys.
*/
class SortStageDefault final : public SortStage {
public:
SortStageDefault(boost::intrusive_ptr<ExpressionContext> expCtx,
WorkingSet* ws,
SortPattern sortPattern,
uint64_t limit,
uint64_t maxMemoryUsageBytes,
bool addSortKeyMetadata,
std::unique_ptr<PlanStage> child);
void spool(WorkingSetID wsid) override final;
void loadingDone() override final {
_sortExecutor.loadingDone();
}
StageState unspool(WorkingSetID* out) override final;
StageType stageType() const final {
return STAGE_SORT_DEFAULT;
}
bool isEOF() final {
return _sortExecutor.isEOF();
}
const SpecificStats* getSpecificStats() const final {
return &_sortExecutor.stats();
}
private:
SortExecutor<SortableWorkingSetMember> _sortExecutor;
};
/**
* Optimized sorting implementation which can be used for WorkingSetMembers in a fetched state that
* have no metadata. This implementation is faster but less general than WorkingSetMemberSortStage.
*
* For performance, this implementation discards record ids and returns WorkingSetMembers in the
* OWNED_OBJ state. Therefore, this sort implementation cannot be used if the plan requires the
* record id to be preserved (e.g. for update or delete plans, where an ancestor stage needs to
* refer to the record in order to perform a write).
*/
class SortStageSimple final : public SortStage {
public:
SortStageSimple(boost::intrusive_ptr<ExpressionContext> expCtx,
WorkingSet* ws,
SortPattern sortPattern,
uint64_t limit,
uint64_t maxMemoryUsageBytes,
bool addSortKeyMetadata,
std::unique_ptr<PlanStage> child);
virtual void spool(WorkingSetID wsid) override final;
void loadingDone() override final {
_sortExecutor.loadingDone();
}
virtual StageState unspool(WorkingSetID* out) override final;
StageType stageType() const final {
return STAGE_SORT_SIMPLE;
}
bool isEOF() final {
return _sortExecutor.isEOF();
}
const SpecificStats* getSpecificStats() const final {
return &_sortExecutor.stats();
}
private:
SortExecutor<BSONObj> _sortExecutor;
};
} // namespace mongo
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