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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/exec/document_value/document.h"
#include "mongo/db/pipeline/variables.h"
namespace mongo {
/**
* 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 a state where all geo metadata is available.
*/
static constexpr auto kAllGeoNearData = QueryMetadataBitSet(
(1 << DocumentMetadataFields::kGeoNearDist) | (1 << DocumentMetadataFields::kGeoNearPoint));
/**
* Represents a state where all metadata is available.
*/
static constexpr auto kAllMetadata =
QueryMetadataBitSet(~(1 << DocumentMetadataFields::kNumFields));
/**
* Represents a state where only text score metadata is available.
*/
static constexpr auto kOnlyTextScore =
QueryMetadataBitSet(1 << DocumentMetadataFields::kTextScore);
/**
* By default, certain metadata is unavailable to the pipeline, unless explicitly specified
* that it is available. This state represents all metadata which is not available by default.
*/
static constexpr auto kDefaultUnavailableMetadata = QueryMetadataBitSet(
(1 << DocumentMetadataFields::kTextScore) | (1 << DocumentMetadataFields::kGeoNearDist) |
(1 << DocumentMetadataFields::kGeoNearPoint));
/**
* Represents a state where no metadata is available.
*/
static constexpr auto kNoMetadata = QueryMetadataBitSet();
DepsTracker(const QueryMetadataBitSet& unavailableMetadata = kNoMetadata)
: _unavailableMetadata{unavailableMetadata} {}
/**
* Returns a projection object covering the non-metadata dependencies tracked by this class, or
* empty BSONObj if the entire document is required.
*/
BSONObj toProjectionWithoutMetadata() const;
bool hasNoRequirements() const {
return fields.empty() && !needWholeDocument && !_metadataDeps.any();
}
/**
* 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 not available to the
* pipeline.
*/
QueryMetadataBitSet getUnavailableMetadata() const {
return _unavailableMetadata;
}
/**
* 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(DocumentMetadataFields::MetaType type, bool required);
/**
* Returns true if the DepsTracker requires that metadata of type 'type' is present.
*/
bool getNeedsMetadata(DocumentMetadataFields::MetaType type) const {
return _metadataDeps[type];
}
/**
* Returns true if there exists a type of metadata required by the DepsTracker.
*/
bool getNeedsAnyMetadata() const {
return _metadataDeps.any();
}
/**
* Return all of the metadata dependencies.
*/
QueryMetadataBitSet& metadataDeps() {
return _metadataDeps;
}
const QueryMetadataBitSet& metadataDeps() const {
return _metadataDeps;
}
/**
* Request that all metadata in the given QueryMetadataBitSet be added as dependencies. Throws a
* UserException if any of the requested metadata fields have been marked as unavailable.
*/
void requestMetadata(const QueryMetadataBitSet& metadata) {
for (size_t i = 1; i < DocumentMetadataFields::kNumFields; ++i) {
if (metadata[i]) {
setNeedsMetadata(static_cast<DocumentMetadataFields::MetaType>(i), true);
}
}
}
/**
* Return fieldpaths ordered such that a parent is immediately before its children.
*/
std::list<std::string> sortedFields() 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:
// Represents all metadata not available to the pipeline.
QueryMetadataBitSet _unavailableMetadata;
// Represents which metadata is used by the pipeline. This is populated while performing
// dependency analysis.
QueryMetadataBitSet _metadataDeps;
};
/** Custom comparator that orders fieldpath strings by path prefix first, then by field.
* This ensures that a parent field is ordered directly before its children.
*/
struct PathPrefixComparator {
/* Returns true if the lhs value should sort before the rhs, false otherwise. */
bool operator()(const std::string& lhs, const std::string& rhs) const;
};
} // namespace mongo
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