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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 <queue>
#include "mongo/db/query/optimizer/cascades/memo.h"
#include "mongo/db/query/optimizer/cascades/rewriter_rules.h"
#include "mongo/db/query/optimizer/utils/utils.h"
namespace mongo::optimizer::cascades {
class LogicalRewriter {
friend class RewriteContext;
public:
/*
* How many times are we allowed to split a sargable node to facilitate index intersection.
* Results in at most 2^N index intersections.
*/
static constexpr size_t kMaxSargableNodeSplitCount = 2;
/**
* Map of rewrite type to rewrite priority
*/
using RewriteSet = opt::unordered_map<LogicalRewriteType, double>;
LogicalRewriter(const Metadata& metadata,
Memo& memo,
PrefixId& prefixId,
RewriteSet rewriteSet,
const DebugInfo& debugInfo,
const QueryHints& hints,
const PathToIntervalFn& pathToInterval,
const ConstFoldFn& constFold,
const LogicalPropsInterface& logicalPropsDerivation,
const CardinalityEstimator& cardinalityEstimator);
// This is a transient structure. We do not allow copying or moving.
LogicalRewriter() = delete;
LogicalRewriter(const LogicalRewriter& other) = delete;
LogicalRewriter(LogicalRewriter&& other) = delete;
LogicalRewriter& operator=(const LogicalRewriter& /*other*/) = delete;
LogicalRewriter& operator=(LogicalRewriter&& /*other*/) = delete;
GroupIdType addRootNode(const ABT& node);
std::pair<GroupIdType, NodeIdSet> addNode(const ABT& node,
GroupIdType targetGroupId,
LogicalRewriteType rule,
bool addExistingNodeWithNewChild);
void clearGroup(GroupIdType groupId);
/**
* Performs logical rewrites across all groups until a fix point is reached.
* Use this method to perform "standalone" rewrites.
*/
bool rewriteToFixPoint();
/**
* Performs rewrites only for a particular group. Use this method to perform rewrites driven by
* top-down optimization.
*/
void rewriteGroup(GroupIdType groupId);
static const RewriteSet& getExplorationSet();
static const RewriteSet& getSubstitutionSet();
private:
using RewriteFn = std::function<void(
LogicalRewriter* rewriter, const MemoLogicalNodeId nodeId, const LogicalRewriteType rule)>;
using RewriteFnMap = opt::unordered_map<LogicalRewriteType, RewriteFn>;
/**
* Attempts to perform a reordering rewrite specified by the R template argument.
*/
template <class AboveType, class BelowType, template <class, class> class R>
void bindAboveBelow(MemoLogicalNodeId nodeMemoId, LogicalRewriteType rule);
/**
* Attempts to perform a simple rewrite specified by the R template argument.
*/
template <class Type, template <class> class R>
void bindSingleNode(MemoLogicalNodeId nodeMemoId, LogicalRewriteType rule);
void registerRewrite(LogicalRewriteType rewriteType, RewriteFn fn);
void initializeRewrites();
static RewriteSet _explorationSet;
static RewriteSet _substitutionSet;
const RewriteSet _activeRewriteSet;
// For standalone logical rewrite phase, keeps track of which groups still have rewrites
// pending.
std::set<int> _groupsPending;
// We don't own those:
const Metadata& _metadata;
Memo& _memo;
PrefixId& _prefixId;
const DebugInfo& _debugInfo;
const QueryHints& _hints;
const PathToIntervalFn& _pathToInterval;
const ConstFoldFn& _constFold;
const LogicalPropsInterface& _logicalPropsDerivation;
const CardinalityEstimator& _cardinalityEstimator;
RewriteFnMap _rewriteMap;
// Contains the set of top-level index fields for a given scanDef. For example "a.b" is encoded
// as "a". This is used to constrain the possible splits of a sargable node.
opt::unordered_map<std::string, FieldNameSet> _indexFieldPrefixMap;
// Track number of times a SargableNode at a given position in the memo has been split.
opt::unordered_map<MemoLogicalNodeId, size_t, NodeIdHash> _sargableSplitCountMap;
};
} // namespace mongo::optimizer::cascades
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