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/**
* Copyright (c) 2014 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 <boost/optional.hpp>
#include <set>
#include <string>
#include "mongo/db/pipeline/document.h"
namespace mongo {
class ParsedDeps;
/**
* This struct allows components in an agg pipeline to report what they need from their input.
*/
struct DepsTracker {
DepsTracker() : needWholeDocument(false), needTextScore(false) {}
/**
* Returns a projection object covering the dependencies tracked by this class.
*/
BSONObj toProjection() const;
boost::optional<ParsedDeps> toParsedDeps() const;
std::set<std::string> fields; // names of needed fields in dotted notation
bool needWholeDocument; // if true, ignore fields and assume the whole document is needed
bool needTextScore;
};
/**
* This class is designed to quickly extract the needed fields from a BSONObj into a Document.
* It should only be created by a call to DepsTracker::ParsedDeps
*/
class ParsedDeps {
public:
Document extractFields(const BSONObj& input) const;
private:
friend struct DepsTracker; // so it can call constructor
explicit ParsedDeps(const Document& fields) : _fields(fields) {}
Document _fields;
};
}
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