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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/cascades/rewriter_rules.h"
#include "mongo/db/query/optimizer/defs.h"
#include "mongo/db/query/optimizer/node.h"
#include "mongo/db/query/optimizer/node_defs.h"
namespace mongo::optimizer::cascades {
/**
* This file contains auxiliary memo structures. Those can be explained without needing access to
* the memo itself.
*/
/**
* Deep hashing, compatible with deep equality comparison.
*/
struct MemoNodeRefHash {
size_t operator()(const ABT::reference_type& nodeRef) const;
};
/**
* Deep equality comparison.
*/
struct MemoNodeRefCompare {
bool operator()(const ABT::reference_type& left, const ABT::reference_type& right) const;
};
/**
* A set of ABT which keeps track of the order in which we inserted them.
*
* Compares ABTs using deep equality.
*/
class OrderPreservingABTSet {
public:
OrderPreservingABTSet() = default;
OrderPreservingABTSet(const OrderPreservingABTSet&) = delete;
OrderPreservingABTSet(OrderPreservingABTSet&&) = default;
OrderPreservingABTSet& operator=(const OrderPreservingABTSet&) = delete;
OrderPreservingABTSet& operator=(OrderPreservingABTSet&&) = default;
ABT::reference_type at(size_t index) const;
std::pair<size_t, bool> emplace_back(ABT node);
boost::optional<size_t> find(ABT::reference_type node) const;
void clear();
size_t size() const;
const ABTVector& getVector() const;
private:
opt::unordered_map<ABT::reference_type, size_t, MemoNodeRefHash, MemoNodeRefCompare> _map;
ABTVector _vector;
};
/**
* Maintains currently best physical node and its associated cost.
*/
struct PhysNodeInfo {
ABT _node;
// Total cost for the entire subtree.
CostType _cost;
// Operator cost (without including the subtree).
CostType _localCost;
// For display purposes, adjusted cardinality based on physical properties (e.g. Repetition and
// Limit-Skip).
CEType _adjustedCE;
// Rule that triggered the creation of this node.
PhysicalRewriteType _rule;
// Node-specific cardinality estimates, for explain.
NodeCEMap _nodeCEMap;
};
/**
* Maintains result of optimization under particular physical properties and a cost limit.
*/
struct PhysOptimizationResult {
PhysOptimizationResult();
PhysOptimizationResult(size_t index, properties::PhysProps physProps, CostType costLimit);
const size_t _index;
const properties::PhysProps _physProps;
CostType _costLimit;
// If set, we have successfully optimized.
boost::optional<PhysNodeInfo> _nodeInfo;
// Rejected physical plans.
std::vector<PhysNodeInfo> _rejectedNodeInfo;
};
using PhysNodeVector = std::vector<std::unique_ptr<PhysOptimizationResult>>;
} // namespace mongo::optimizer::cascades
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