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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"
namespace mongo::optimizer {
class PathFusion {
enum class Type { unknown, nothing, object, array, boolean, any };
enum class Kind { project, filter };
struct CollectedInfo {
bool isNotNothing() const {
return _type != Type::unknown && _type != Type::nothing;
}
Type _type{Type::unknown};
// Is the result of the path independent of its input (e.g. can be if the paths terminates
// with PathConst, but not necessarily with PathIdentity).
bool _isConst{false};
};
public:
PathFusion(VariableEnvironment& env) : _env(env) {}
template <typename T, typename... Ts>
void transport(ABT&, const T& op, Ts&&...) {
if constexpr (std::is_base_of_v<PathSyntaxSort, T>) {
_info[&op] = CollectedInfo{};
}
}
void transport(ABT& n, const PathConstant&, ABT& c);
void transport(ABT& n, const PathCompare&, ABT& c);
void transport(ABT& n, const PathGet&, ABT& path);
void transport(ABT& n, const PathField&, ABT& path);
void transport(ABT& n, const PathTraverse&, ABT& inner);
void transport(ABT& n, const PathComposeM&, ABT& p1, ABT& p2);
void prepare(ABT& n, const EvalPath& eval) {
_kindCtx.push_back(Kind::project);
}
void transport(ABT& n, const EvalPath& eval, ABT& path, ABT& input);
void prepare(ABT& n, const EvalFilter& eval) {
_kindCtx.push_back(Kind::filter);
}
void transport(ABT& n, const EvalFilter& eval, ABT& path, ABT& input);
bool optimize(ABT& root);
private:
ABT::reference_type follow(ABT::reference_type n);
ABT::reference_type follow(const ABT& n) {
return follow(n.ref());
}
bool fuse(ABT& lhs, const ABT& rhs);
VariableEnvironment& _env;
opt::unordered_map<const PathSyntaxSort*, CollectedInfo> _info;
opt::unordered_set<const PathSyntaxSort*> _redundant;
// A stack of context (either project or filter path)
std::vector<Kind> _kindCtx;
bool _changed{false};
};
} // namespace mongo::optimizer
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