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/**
* Copyright (C) 2022-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/query/optimizer/reference_tracker.h"
#include "mongo/db/query/optimizer/utils/abt_hash.h"
namespace mongo::optimizer {
using DisableInlineFn = std::function<bool(const ABT&)>;
/**
* This is an example rewriter that does constant evaluation in-place.
*/
class ConstEval {
public:
ConstEval(VariableEnvironment& env,
DisableInlineFn disableInline = {},
ProjectionNameSet* erasedProjNames = nullptr)
: _env(env), _erasedProjNames(std::move(erasedProjNames)), _disableInline(disableInline) {}
// The default noop transport. Note the first ABT& parameter.
template <typename T, typename... Ts>
void transport(ABT&, const T&, Ts&&...) {}
void transport(ABT& n, const Variable& var);
void prepare(ABT&, const Let& let);
void transport(ABT& n, const Let& let, ABT&, ABT& in);
void transport(ABT& n, const LambdaApplication& app, ABT& lam, ABT& arg);
void prepare(ABT&, const LambdaAbstraction&);
void transport(ABT&, const LambdaAbstraction&, ABT&);
// Specific transport for binary operation
// The const correctness is probably wrong (as const ABT& lhs, const ABT& rhs does not work for
// some reason but we can fix it later).
void transport(ABT& n, const BinaryOp& op, ABT& lhs, ABT& rhs);
void transport(ABT& n, const FunctionCall& op, std::vector<ABT>& args);
void transport(ABT& n, const If& op, ABT& cond, ABT& thenBranch, ABT& elseBranch);
void transport(ABT& n, const EvaluationNode& op, ABT& child, ABT& expr);
void prepare(ABT&, const PathTraverse&);
void transport(ABT&, const PathTraverse&, ABT&);
void transport(ABT& n, const PathComposeM& op, ABT& lhs, ABT& rhs);
void transport(ABT& n, const PathComposeA& op, ABT& lhs, ABT& rhs);
void prepare(ABT&, const References& refs);
void transport(ABT& n, const References& op, std::vector<ABT>&);
// The tree is passed in as NON-const reference as we will be updating it.
bool optimize(ABT& n);
private:
struct EvalNodeHash {
size_t operator()(const EvaluationNode* node) const {
return ABTHashGenerator::generate(node->getProjection());
}
};
struct EvalNodeCompare {
size_t operator()(const EvaluationNode* lhs, const EvaluationNode* rhs) const {
return lhs->getProjection() == rhs->getProjection();
}
};
struct RefHash {
size_t operator()(const ABT::reference_type& nodeRef) const {
return nodeRef.hash();
}
};
void swapAndUpdate(ABT& n, ABT newN);
void removeUnusedEvalNodes();
VariableEnvironment& _env;
// Optionally collect projection names from erased Eval nodes.
ProjectionNameSet* _erasedProjNames;
// Used to indicate if a given Evaluation node should not be inlined.
DisableInlineFn _disableInline;
opt::unordered_set<const Variable*> _singleRef;
opt::unordered_set<const EvaluationNode*> _noRefProj;
opt::unordered_map<const Let*, std::vector<const Variable*>> _letRefs;
opt::unordered_map<const EvaluationNode*, std::vector<const Variable*>> _projectRefs;
opt::unordered_set<const EvaluationNode*, EvalNodeHash, EvalNodeCompare> _seenProjects;
opt::unordered_set<ABT::reference_type, RefHash> _inlinedDefs;
opt::unordered_map<ABT::reference_type, ABT::reference_type, RefHash> _staleDefs;
// We collect old ABTs in order to avoid the ABA problem.
std::vector<ABT> _staleABTs;
bool _inRefBlock{false};
size_t _inCostlyCtx{0};
bool _changed{false};
};
} // namespace mongo::optimizer
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