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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/base/disallow_copying.h"
#include "mongo/db/catalog/collection_options.h"
#include "mongo/db/operation_context.h"
#include "mongo/util/string_map.h"
#include "mongo/util/uuid.h"
namespace mongo {
extern bool debugCollectionUUIDs;
/**
* This class comprises the NamespaceString to UUID cache that prevents given namespaces
* from resolving to multiple UUIDs.
*/
using CollectionUUID = UUID;
class Database;
class NamespaceUUIDCache {
MONGO_DISALLOW_COPYING(NamespaceUUIDCache);
public:
static const OperationContext::Decoration<NamespaceUUIDCache> get;
NamespaceUUIDCache() = default;
/**
* This function adds the pair nss.ns(), uuid to the namespace UUID cache
* if it does not yet exist. If nss.ns() already exists in the cache with
* a different UUID, a AssertionException is thrown, so we can guarantee that
* an operation will always resolve the same name to the same collection,
* even in presence of drops and renames.
*/
void ensureNamespaceInCache(const NamespaceString& nss, CollectionUUID uuid);
/**
* This function removes the entry for nss.ns() from the namespace UUID
* cache. Does nothing if the entry doesn't exist. It is called via the
* op observer when a collection is dropped or renamed.
*/
void evictNamespace(const NamespaceString& nss);
/**
* Same as above, but for all registered namespaces in the given dbname.
*/
void evictNamespacesInDatabase(StringData dbname);
/**
* For testing only: verify that 'nss' is not cached.
*/
void verifyNotCached(const NamespaceString& nss, CollectionUUID uuid) {
auto it = _cache.find(nss.ns());
invariant(it == _cache.end() || it->second != uuid);
}
private:
using CollectionUUIDMap = StringMap<CollectionUUID>;
CollectionUUIDMap _cache;
};
} // namespace mongo
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