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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"
#include "mongo/db/pipeline/variables.h"
namespace mongo {
class ParsedDeps;
/**
* This struct allows components in an agg pipeline to report what they need from their input.
*/
struct DepsTracker {
/**
* Represents what metadata is available on documents that are input to the pipeline.
*/
enum MetadataAvailable { kNoMetadata = 0, kTextScore = 1 };
DepsTracker(MetadataAvailable metadataAvailable = kNoMetadata)
: _metadataAvailable(metadataAvailable) {}
/**
* Returns a projection object covering the dependencies tracked by this class.
*/
BSONObj toProjection() const;
boost::optional<ParsedDeps> toParsedDeps() const;
bool hasNoRequirements() const {
return fields.empty() && !needWholeDocument && !_needTextScore;
}
/**
* Returns 'true' if any of the DepsTracker's variables appear in the passed 'ids' set.
*/
bool hasVariableReferenceTo(const std::set<Variables::Id>& ids) const {
std::vector<Variables::Id> match;
std::set_intersection(
vars.begin(), vars.end(), ids.begin(), ids.end(), std::back_inserter(match));
return !match.empty();
}
MetadataAvailable getMetadataAvailable() const {
return _metadataAvailable;
}
bool isTextScoreAvailable() const {
return _metadataAvailable & MetadataAvailable::kTextScore;
}
bool getNeedTextScore() const {
return _needTextScore;
}
void setNeedTextScore(bool needTextScore) {
if (needTextScore && !isTextScoreAvailable()) {
uasserted(
40218,
"pipeline requires text score metadata, but there is no text score available");
}
_needTextScore = needTextScore;
}
bool getNeedSortKey() const {
return _needSortKey;
}
void setNeedSortKey(bool needSortKey) {
// We don't expect to ever unset '_needSortKey'.
invariant(!_needSortKey || needSortKey);
_needSortKey = needSortKey;
}
std::set<std::string> fields; // Names of needed fields in dotted notation.
std::set<Variables::Id> vars; // IDs of referenced variables.
bool needWholeDocument = false; // If true, ignore 'fields'; the whole document is needed.
private:
/**
* Appends the meta projections for the sort key and/or text score to 'bb' if necessary. Returns
* true if either type of metadata was needed, and false otherwise.
*/
bool _appendMetaProjections(BSONObjBuilder* bb) const;
MetadataAvailable _metadataAvailable;
bool _needTextScore = false; // if true, add a {$meta: "textScore"} to the projection.
bool _needSortKey = false; // if true, add a {$meta: "sortKey"} to the projection.
};
/**
* 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(Document&& fields) : _fields(std::move(fields)), _nFields(_fields.size()) {}
Document _fields;
int _nFields; // Cache the number of top-level fields needed.
};
}
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