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/**
* Copyright (C) 2020-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 <queue>
#include "mongo/db/exec/sbe/stages/stages.h"
#include "mongo/db/exec/sbe/stages/sorted_stream_merger.h"
namespace mongo::sbe {
/**
* Merges the outputs of N children, each of which is sorted. The output is also sorted.
*
* This stage is a binding reflector.
*/
class SortedMergeStage final : public PlanStage {
public:
/**
* Constructor. Arguments:
* -inputStages: Array of child stages. Each stage must return results in sorted order.
* -inputKeys: Element 'i' of this vector describes which slots the sort key can be found in
* for child 'i'. Each element of this vector should have the same size as 'dirs'.
* -dirs: Describes how to interpret the sort key.
* -inputVals: Similar layout to 'inputKeys' but the slots hold additional values that should
* be propagated.
* -outputVals: Slots where the output should be stored.
*/
SortedMergeStage(PlanStage::Vector inputStages,
// Each element of 'inputKeys' must be the same size as 'dirs'.
std::vector<value::SlotVector> inputKeys,
// Sort directions. Used to interpret each input key.
std::vector<value::SortDirection> dirs,
// Each element of 'inputVals' must be the same size as 'outputVals'.
std::vector<value::SlotVector> inputVals,
value::SlotVector outputVals,
PlanNodeId planNodeId,
bool participateInTrialRunTracking = true);
std::unique_ptr<PlanStage> clone() const final;
void prepare(CompileCtx& ctx) final;
value::SlotAccessor* getAccessor(CompileCtx& ctx, value::SlotId slot) final;
void open(bool reOpen) final;
PlanState getNext() final;
void close() final;
std::unique_ptr<PlanStageStats> getStats(bool includeDebugInfo) const final;
const SpecificStats* getSpecificStats() const final;
std::vector<DebugPrinter::Block> debugPrint() const final;
size_t estimateCompileTimeSize() const final;
private:
const std::vector<value::SlotVector> _inputKeys;
const std::vector<value::SortDirection> _dirs;
const std::vector<value::SlotVector> _inputVals;
const value::SlotVector _outputVals;
std::vector<value::SwitchAccessor> _outAccessors;
// Maintains state about merging the results in order. Initialized during prepare().
boost::optional<SortedStreamMerger<PlanStage>> _merger;
};
} // namespace mongo::sbe
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