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/**
* Copyright (C) 2022-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/db/namespace_string.h"
#include "mongo/s/catalog/type_index_catalog_gen.h"
#include "mongo/s/index_version.h"
#include "mongo/util/read_through_cache.h"
namespace mongo {
using IndexCatalogTypeMap = StringMap<IndexCatalogType>;
class GlobalIndexesCache {
public:
GlobalIndexesCache(boost::optional<Timestamp> indexVersion, IndexCatalogTypeMap&& indexes)
: _indexVersion(indexVersion), _indexes(indexes) {}
bool empty() const;
boost::optional<Timestamp> getVersion() const;
size_t numIndexes() const;
bool contains(const StringData& name) const;
void add(const IndexCatalogType& index, const Timestamp& indexVersion);
void remove(const StringData& name, const Timestamp& indexVersion);
void clear();
private:
boost::optional<Timestamp> _indexVersion;
IndexCatalogTypeMap _indexes;
};
/**
* Constructed to be used exclusively by the CatalogCache as a vector clock (Time) to drive
* IndexCache's lookups.
*
* This class wraps an IndexVersion timestamp with a disambiguating sequence number and a forced
* refresh sequence number. When a collection is dropped and recreated, the index version resets to
* boost::none. This cannot be compared with a valid timestamp, so the disambiguatingSequenceNumber
* is used to compare those cases.
*
* Two ComparableIndexVersions with no indexes (boost::none timestamp) will always be the same
* regardless of the collection they refer to.
*/
class ComparableIndexVersion {
public:
/**
* Creates a ComparableIndexVersion that wraps the CollectionIndexes' timestamp.
*/
static ComparableIndexVersion makeComparableIndexVersion(
const boost::optional<Timestamp>& version);
/**
* Creates a new instance which will artificially be greater than any previously created
* ComparableIndexVersion and smaller than any instance created afterwards. Used as means to
* cause the collections cache to attempt a refresh in situations where causal consistency
* cannot be inferred.
*/
static ComparableIndexVersion makeComparableIndexVersionForForcedRefresh();
/**
* Empty constructor needed by the ReadThroughCache.
*/
ComparableIndexVersion() = default;
std::string toString() const;
bool operator==(const ComparableIndexVersion& other) const;
bool operator!=(const ComparableIndexVersion& other) const {
return !(*this == other);
}
/**
* Two boost::none timestamps will always evaluate as equal. If one version is boost::none and
* the other has a timestamp, the comparison will depend on the disambiguating sequence number.
*/
bool operator<(const ComparableIndexVersion& other) const;
bool operator>(const ComparableIndexVersion& other) const {
return other < *this;
}
bool operator<=(const ComparableIndexVersion& other) const {
return !(*this > other);
}
bool operator>=(const ComparableIndexVersion& other) const {
return !(*this < other);
}
private:
friend class CatalogCache;
static AtomicWord<uint64_t> _disambiguatingSequenceNumSource;
static AtomicWord<uint64_t> _forcedRefreshSequenceNumSource;
ComparableIndexVersion(uint64_t forcedRefreshSequenceNum,
boost::optional<Timestamp> version,
uint64_t disambiguatingSequenceNum)
: _forcedRefreshSequenceNum(forcedRefreshSequenceNum),
_indexVersion(std::move(version)),
_disambiguatingSequenceNum(disambiguatingSequenceNum) {}
void setCollectionIndexes(const boost::optional<Timestamp>& version);
uint64_t _forcedRefreshSequenceNum{0};
boost::optional<Timestamp> _indexVersion;
// Locally incremented sequence number that allows to compare two versions where one is
// boost::none and the other has a timestamp. Two boost::none versions with different
// disambiguating sequence numbers are still considered equal.
uint64_t _disambiguatingSequenceNum{0};
};
/**
* This intermediate structure is necessary to be able to store collections without any global
* indexes in the cache. The cache does not allow for an empty value, so this intermediate structure
* is needed.
*/
struct OptionalGlobalIndexesInfo {
// No indexes constructor.
OptionalGlobalIndexesInfo() = default;
// Constructor with global indexes
OptionalGlobalIndexesInfo(GlobalIndexesCache gii) : optGii(std::move(gii)) {}
// If nullptr, the collection has an index version of boost::none and no global indexes.
// Otherwise, the index version is some valid timestamp (there still may be no global indexes).
boost::optional<GlobalIndexesCache> optGii;
};
using GlobalIndexesCacheBase =
ReadThroughCache<NamespaceString, OptionalGlobalIndexesInfo, ComparableIndexVersion>;
} // namespace mongo
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