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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 "mongo/bson/bsonobj.h"
#include "mongo/db/exec/working_set.h"
#include "mongo/db/index/btree_key_generator.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/query/collation/collator_interface.h"
namespace mongo {
class SortKeyGenerator {
public:
/**
* Metadata about a document which is needed to produce keys for $meta sort. The client of the
* SortKeyGenerator must provide this metadata in order to correctly obtain sort keys for sort
* patterns with $meta.
*/
struct Metadata {
double textScore = 0.0;
double randVal = 0.0;
};
/**
* Constructs a sort key generator which will generate keys for sort pattern 'sortSpec'. The
* keys will incorporate the collation given by 'collator', and thus when actually compared to
* one another should use the simple collation.
*/
SortKeyGenerator(const BSONObj& sortSpec, const CollatorInterface* collator);
/**
* Returns the key which should be used to sort the WorkingSetMember, or a non-OK status if no
* key could be generated. The WorkingSetMember may represent either an index key, or a document
* (owned or unowned) that has been fetched from the collection.
*
* If the sort pattern contains a $meta sort (e.g. sort by "textScore" or "randVal"), then the
* necessary metadata is obtained from the WorkingSetMember.
*/
StatusWith<BSONObj> getSortKey(const WorkingSetMember&) const;
/**
* Returns the key which should be used to sort 'obj', or a non-OK status if no key could be
* generated.
*
* The caller must supply the appropriate 'metadata' in the case that the sort pattern includes
* a $meta sort (i.e. if sortHasMeta() is true). These values are filled in at the corresponding
* positions in the sort key.
*/
StatusWith<BSONObj> getSortKeyFromDocument(const BSONObj& obj, const Metadata*) const;
private:
// Describes whether a component of the sort pattern is a field path (e.g. sort by "a.b"), or
// else describes the type of $meta sort.
enum class SortPatternPartType {
kFieldPath,
kMetaTextScore,
kMetaRandVal,
};
// Extracts the sort key from a WorkingSetMember which represents an index key. It is illegal to
// call this if the working set member is not in RID_AND_IDX state. It is also illegal to call
// this if the sort pattern has any $meta components.
StatusWith<BSONObj> getSortKeyFromIndexKey(const WorkingSetMember& member) const;
// Extracts the sort key from 'obj', using '_sortSpecWithoutMeta' and thus ignoring any $meta
// sort components of the sort pattern. The caller is responsible for augmenting this key with
// the appropriate metadata if '_sortHasMeta' is true.
StatusWith<BSONObj> getSortKeyFromDocumentWithoutMetadata(const BSONObj& obj) const;
const CollatorInterface* _collator = nullptr;
// The sort pattern with any $meta sort components stripped out, since the underlying index key
// generator does not understand $meta sort.
BSONObj _sortSpecWithoutMeta;
// For each element of the raw sort spec, describes whether the element is sorting by a field
// path or by a particular meta-sort.
std::vector<SortPatternPartType> _patternPartTypes;
// If we're not sorting with a $meta value we can short-cut some work.
bool _sortHasMeta = false;
std::unique_ptr<BtreeKeyGenerator> _indexKeyGen;
};
} // namespace mongo
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