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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 <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 {
/**
* Used by aggregation stages to report whether or not dependency resolution is complete, or
* must continue to the next stage.
*/
enum State {
// The full object and all metadata may be required.
NOT_SUPPORTED = 0x0,
// Later stages could need either fields or metadata. For example, a $limit stage will pass
// through all fields, and they may or may not be needed by future stages.
SEE_NEXT = 0x1,
// Later stages won't need more fields from input. For example, an inclusion projection like
// {_id: 1, a: 1} will only output two fields, so future stages cannot possibly depend on
// any other fields.
EXHAUSTIVE_FIELDS = 0x2,
// Later stages won't need more metadata from input. For example, a $group stage will group
// documents together, discarding their text score and sort keys.
EXHAUSTIVE_META = 0x4,
// Later stages won't need either fields or metadata.
EXHAUSTIVE_ALL = EXHAUSTIVE_FIELDS | EXHAUSTIVE_META,
};
/**
* Represents the type of metadata a pipeline might request.
*/
enum class MetadataType {
// The score associated with a text match.
TEXT_SCORE,
// The key to use for sorting.
SORT_KEY,
// The computed distance for a near query.
GEO_NEAR_DISTANCE,
// The point used in the computation of the GEO_NEAR_DISTANCE.
GEO_NEAR_POINT,
};
/**
* Represents what metadata is available on documents that are input to the pipeline.
*/
enum MetadataAvailable {
kNoMetadata = 0,
kTextScore = 1 << 1,
kGeoNearDistance = 1 << 2,
kGeoNearPoint = 1 << 3,
};
/**
* Represents a state where all geo metadata is available.
*/
static constexpr auto kAllGeoNearDataAvailable =
MetadataAvailable(MetadataAvailable::kGeoNearDistance | MetadataAvailable::kGeoNearPoint);
/**
* Represents a state where all metadata is available.
*/
static constexpr auto kAllMetadataAvailable =
MetadataAvailable(kTextScore | kGeoNearDistance | kGeoNearPoint);
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();
}
/**
* Returns a value with bits set indicating the types of metadata available.
*/
MetadataAvailable getMetadataAvailable() const {
return _metadataAvailable;
}
/**
* Returns true if the DepsTracker the metadata 'type' is available to the pipeline. It is
* illegal to call this with MetadataType::SORT_KEY, since the sort key will always be available
* if needed.
*/
bool isMetadataAvailable(MetadataType type) const;
/**
* Sets whether or not metadata 'type' is required. Throws if 'required' is true but that
* metadata is not available to the pipeline.
*
* Except for MetadataType::SORT_KEY, once 'type' is required, it cannot be unset.
*/
void setNeedsMetadata(MetadataType type, bool required);
/**
* Returns true if the DepsTracker requires that metadata of type 'type' is present.
*/
bool getNeedsMetadata(MetadataType type) const;
/**
* Returns true if there exists a type of metadata required by the DepsTracker.
*/
bool getNeedsAnyMetadata() const {
return _needTextScore || _needSortKey || _needGeoNearDistance || _needGeoNearPoint;
}
/**
* Returns a vector containing all the types of metadata required by this DepsTracker.
*/
std::vector<MetadataType> getAllRequiredMetadataTypes() const;
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;
// Each member variable influences a different $meta projection.
bool _needTextScore = false; // {$meta: "textScore"}
bool _needSortKey = false; // {$meta: "sortKey"}
bool _needGeoNearDistance = false; // {$meta: "geoNearDistance"}
bool _needGeoNearPoint = false; // {$meta: "geoNearPoint"}
};
/**
* 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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