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// expression_algo.h
/**
* Copyright (C) 2015 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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 <memory>
#include <set>
#include "mongo/base/string_data.h"
#include "mongo/stdx/functional.h"
#include "mongo/util/string_map.h"
namespace mongo {
class MatchExpression;
struct DepsTracker;
namespace expression {
using NodeTraversalFunc = stdx::function<void(MatchExpression*, std::string)>;
/**
* Returns true if the documents matched by 'lhs' are a subset of the documents matched by
* 'rhs', i.e. a document matched by 'lhs' must also be matched by 'rhs', and false otherwise.
*
* With respect to partial indexes, 'lhs' corresponds to the query specification and 'rhs'
* corresponds to the filter specification.
*
* e.g.
*
* Suppose that
*
* lhs = { x : 4 }
* rhs = { x : { $lte : 5 } }
*
* ==> true
*
* Suppose that
*
* lhs = { x : { $gte: 6 } }
* rhs = { x : 7 }
*
* ==> false
*/
bool isSubsetOf(const MatchExpression* lhs, const MatchExpression* rhs);
/**
* Determine if it is possible to split 'expr' into two MatchExpressions, where one is not
* dependent on any path from 'pathSet', such that applying the two in sequence is equivalent
* to applying 'expr'.
*
* For example, {a: "foo", b: "bar"} is splittable by "b", while
* {$or: [{a: {$eq: "foo"}}, {b: {$eq: "bar"}}]} is not splittable by "b", due to the $or.
*/
bool isSplittableBy(const MatchExpression& expr, const std::set<std::string>& pathSet);
/**
* Determine if 'expr' is reliant upon any path from 'pathSet'.
*/
bool isIndependentOf(const MatchExpression& expr, const std::set<std::string>& pathSet);
/**
* Returns whether the path represented by 'first' is an prefix of the path represented by 'second'.
* Equality is not considered a prefix. For example:
*
* a.b is a prefix of a.b.c
* a.b is not a prefix of a.balloon
* a is a prefix of a.b
* a is not a prefix of a
* a.b is not a prefix of a
*/
bool isPathPrefixOf(StringData first, StringData second);
/**
* Applies 'func' to each node of 'expr', where the first argument is a pointer to that actual node
* (not a copy), and the second argument is the path to that node. Callers should not depend on the
* order of the traversal of the nodes.
*/
void mapOver(MatchExpression* expr, NodeTraversalFunc func, std::string path = "");
/**
* Attempt to split 'expr' into two MatchExpressions, where the first is not reliant upon any
* path from 'fields', such that applying the matches in sequence is equivalent to applying
* 'expr'. Takes ownership of 'expr'.
*
* If 'expr' cannot be split, returns {nullptr, expr}. If 'expr' is entirely independent of
* 'fields', returns {expr, nullptr}. If 'expr' is partially dependent on 'fields', and partially
* independent, returns {exprLeft, exprRight}, where each new MatchExpression contains a portion of
* 'expr'.
*
* Any paths which should be renamed are encoded in 'renames', which maps from path names in 'expr'
* to the new values of those paths. If the return value is {exprLeft, exprRight} or {exprLeft,
* nullptr}, exprLeft will reflect the path renames. For example, suppose the original match
* expression is {old: {$gt: 3}} and 'renames' contains the mapping "old" => "new". The returned
* exprLeft value will be {new: {$gt: 3}}, provided that "old" is not in 'fields'.
*
* Never returns {nullptr, nullptr}.
*/
std::pair<std::unique_ptr<MatchExpression>, std::unique_ptr<MatchExpression>>
splitMatchExpressionBy(std::unique_ptr<MatchExpression> expr,
const std::set<std::string>& fields,
const StringMap<std::string>& renames);
} // namespace expression
} // namespace mongo
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