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/**
* Copyright (C) 2021-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 <vector>
#include "mongo/db/exec/sbe/stages/stages.h"
#include "mongo/db/exec/sbe/vm/vm.h"
namespace mongo::sbe {
/**
* This stage performs a merge join given an outer and an inner child stage. The stage remaps
* both the outer side (buffer to support full cross product) and the inner side to buffer inner
* values to survive yielding. The join is an equi-join where the join key from the outer side is
* given by the 'outerKeys' slot vector and the join key from the inner side is given by the
* 'innerKeys' slot vector. In addition, each resulting row returned by the join has the
* 'outerProjects' values from the outer side and the 'innerProjects' values from the inner side.
*
* The stage expects the data to be sorted according to the 'sortDirs' parameter. This describes the
* sort direction for each of keys on which we are joining, so the 'sortDirs', 'outerKeys', and
* 'innerKeys' vectors must each be the same length.
*
* Debug string format:
*
* mj [asc|desc, ...]
* left [<outer keys>] [<outer projects>] childStage
* right [<inner keys>] [<inner projects>] childStage
*/
class MergeJoinStage final : public PlanStage {
public:
MergeJoinStage(std::unique_ptr<PlanStage> outer,
std::unique_ptr<PlanStage> inner,
value::SlotVector outerKeys,
value::SlotVector outerProjects,
value::SlotVector innerKeys,
value::SlotVector innerProjects,
std::vector<value::SortDirection> sortDirs,
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;
protected:
void doSaveState(bool relinquishCursor) final;
private:
using MergeJoinBuffer = std::vector<value::MaterializedRow>;
using MergeJoinBufferAccessor = value::MaterializedRowAccessor<MergeJoinBuffer>;
const value::SlotVector _outerKeys;
const value::SlotVector _outerProjects;
const value::SlotVector _innerKeys;
const value::SlotVector _innerProjects;
const std::vector<value::SortDirection> _dirs;
// All defined values / projects from the outer side.
value::SlotAccessorMap _outOuterAccessors;
// Accessors for outer projects in the buffer.
std::vector<std::unique_ptr<MergeJoinBufferAccessor>> _outOuterProjectAccessors;
// Accessors for the inner projects, values are buffered to survive yielding.
std::vector<std::unique_ptr<value::MaterializedSingleRowAccessor>> _outInnerProjectAccessors;
// Accessors for keys which are equivalent for both outer and inner sides.
std::vector<std::unique_ptr<value::MaterializedSingleRowAccessor>> _outOuterInnerKeyAccessors;
// Buffer and its iterator for holding buffered outer projects.
MergeJoinBuffer _outerProjectsBuffer;
size_t _outerProjectsBufferIt{0};
// Key for the outer projects buffer. All rows in the buffer should have this same key.
value::MaterializedRow _bufferKey;
std::vector<value::SlotAccessor*> _outerKeyAccessors;
std::vector<value::SlotAccessor*> _outerProjectAccessors;
std::vector<value::SlotAccessor*> _innerKeyAccessors;
std::vector<value::SlotAccessor*> _innerProjectAccessors;
// The current keys from the outer and inner sides buffered into MaterializedRow's after each
// side has advanced.
value::MaterializedRow _currentOuterKey;
value::MaterializedRow _currentInnerKey;
// The current project values from inner side buffered into a MaterializedRow after the inner
// has advanced.
value::MaterializedRow _currentInnerProject;
// Comparators for keys from the other and inner sides buffered into MaterializedRow's.
const value::MaterializedRowEq _rowEq;
const value::MaterializedRowLess _rowLt;
// For when need to EOF earlier after exhausting all of the rows from the outer side.
bool _isOuterDone{false};
};
} // namespace mongo::sbe
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