diff options
Diffstat (limited to 'src/mongo/db/exec/sbe/stages/traverse.h')
-rw-r--r-- | src/mongo/db/exec/sbe/stages/traverse.h | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/src/mongo/db/exec/sbe/stages/traverse.h b/src/mongo/db/exec/sbe/stages/traverse.h new file mode 100644 index 00000000000..fb7555b745e --- /dev/null +++ b/src/mongo/db/exec/sbe/stages/traverse.h @@ -0,0 +1,112 @@ +/** + * Copyright (C) 2019-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 "mongo/db/exec/sbe/expressions/expression.h" +#include "mongo/db/exec/sbe/stages/stages.h" +#include "mongo/db/exec/sbe/vm/vm.h" + +namespace mongo::sbe { +/** + * This is an array traversal operator. If the input value coming from the 'outer' side is an array + * then we execute the 'inner' side exactly once for every element of the array. The results from + * the 'inner' side are then collected into the output array value. The traversal is recursive and + * the structure of nested arrays is preserved (up to optional depth). If the input value is not an + * array then we execute the inner side just once and return the result. + * + * If an optional 'fold' expression is provided then instead of the output array we combine + * individual results into a single output value. Another expression 'final' controls optional + * short-circuiting (a.k.a. early out) logic. + */ +class TraverseStage final : public PlanStage { +public: + TraverseStage(std::unique_ptr<PlanStage> outer, + std::unique_ptr<PlanStage> inner, + value::SlotId inField, + value::SlotId outField, + value::SlotId outFieldInner, + value::SlotVector outerCorrelated, + std::unique_ptr<EExpression> foldExpr, + std::unique_ptr<EExpression> finalExpr, + boost::optional<size_t> nestedArraysDepth = boost::none); + + 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() const final; + const SpecificStats* getSpecificStats() const final; + std::vector<DebugPrinter::Block> debugPrint() const final; + +private: + void openInner(value::TypeTags tag, value::Value val); + bool traverse(value::SlotAccessor* inFieldAccessor, + value::OwnedValueAccessor* outFieldOutputAccessor, + size_t level); + + // The input slot holding value being traversed. + const value::SlotId _inField; + + // The output slot holding result of the traversal. + const value::SlotId _outField; + + // The result of a single iteration of the traversal. + const value::SlotId _outFieldInner; + + // Slots from the 'outer' side that are explicitly accessible on the 'inner' side. + const value::SlotVector _correlatedSlots; + + // Optional folding expression for combining array elements. + const std::unique_ptr<EExpression> _fold; + + // Optional boolean expression controlling short-circuiting of the fold. + const std::unique_ptr<EExpression> _final; + + // Optional nested arrays recursion depth. + const boost::optional<size_t> _nestedArraysDepth; + + value::SlotAccessor* _inFieldAccessor{nullptr}; + value::ViewOfValueAccessor _correlatedAccessor; + value::OwnedValueAccessor _outFieldOutputAccessor; + value::SlotAccessor* _outFieldInputAccessor{nullptr}; + + std::unique_ptr<vm::CodeFragment> _foldCode; + std::unique_ptr<vm::CodeFragment> _finalCode; + + vm::ByteCode _bytecode; + + bool _compiled{false}; + bool _reOpenInner{false}; +}; +} // namespace mongo::sbe |