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/**
* Copyright (C) 2018-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 <string>
#include <vector>
#include "mongo/db/matcher/expression.h"
#include "mongo/db/matcher/expression_leaf.h"
#include "mongo/db/matcher/expression_tree.h"
#include "mongo/db/pipeline/expression.h"
namespace mongo {
class RewriteExpr final {
public:
/**
* Holds the result of an Expression rewrite operation.
*/
class RewriteResult final {
public:
RewriteResult(std::unique_ptr<MatchExpression> matchExpression,
std::vector<BSONObj> matchExprElemStorage)
: _matchExpression(std::move(matchExpression)),
_matchExprElemStorage(std::move(matchExprElemStorage)) {}
MatchExpression* matchExpression() const {
return _matchExpression.get();
}
std::unique_ptr<MatchExpression> releaseMatchExpression() {
return std::move(_matchExpression);
}
RewriteResult clone() const {
auto clonedMatch = _matchExpression ? _matchExpression->shallowClone() : nullptr;
return {std::move(clonedMatch), _matchExprElemStorage};
}
private:
std::unique_ptr<MatchExpression> _matchExpression;
// MatchExpression nodes are constructed with BSONElement arguments that are externally
// owned and expected to outlive the MatchExpression. '_matchExprElemStorage' holds the
// underlying BSONObj storage for these arguments.
std::vector<BSONObj> _matchExprElemStorage;
};
/**
* Attempts to construct a MatchExpression that will match against either an identical set or a
* superset of the documents matched by 'expr'. Returns the MatchExpression as a RewriteResult.
* If a rewrite is not possible, RewriteResult::matchExpression() will return a nullptr.
*/
static RewriteResult rewrite(const boost::intrusive_ptr<Expression>& expr,
const CollatorInterface* collator);
private:
RewriteExpr(const CollatorInterface* collator) : _collator(collator) {}
// Returns rewritten MatchExpression or null unique_ptr if not rewritable.
std::unique_ptr<MatchExpression> _rewriteExpression(
const boost::intrusive_ptr<Expression>& currExprNode);
// Returns rewritten MatchExpression or null unique_ptr if not rewritable.
std::unique_ptr<MatchExpression> _rewriteAndExpression(
const boost::intrusive_ptr<ExpressionAnd>& currExprNode);
// Returns rewritten MatchExpression or null unique_ptr if not rewritable.
std::unique_ptr<MatchExpression> _rewriteOrExpression(
const boost::intrusive_ptr<ExpressionOr>& currExprNode);
// Returns rewritten MatchExpression or null unique_ptr if not rewritable.
std::unique_ptr<MatchExpression> _rewriteComparisonExpression(
const boost::intrusive_ptr<ExpressionCompare>& expr);
bool _canRewriteComparison(const boost::intrusive_ptr<ExpressionCompare>& expr) const;
std::unique_ptr<MatchExpression> _buildComparisonMatchExpression(
ExpressionCompare::CmpOp comparisonOp, BSONElement fieldAndValue);
std::vector<BSONObj> _matchExprElemStorage;
const CollatorInterface* _collator;
};
} // namespace mongo
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