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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/catalog/collection.h"
#include "mongo/db/db_raii.h"
namespace mongo {
/**
* Class which holds a set of pointers to multiple collections. This class distinguishes between
* a 'main collection' and 'secondary collections'. While the former represents the collection a
* given command is run against, the latter represents other collections that the query execution
* engine may need to access.
*/
class MultipleCollectionAccessor final {
public:
MultipleCollectionAccessor() = default;
MultipleCollectionAccessor(OperationContext* opCtx,
const CollectionPtr* mainColl,
const NamespaceString& mainCollNss,
bool isAnySecondaryNamespaceAViewOrSharded,
const std::vector<NamespaceStringOrUUID>& secondaryExecNssList)
: _mainColl(mainColl),
_isAnySecondaryNamespaceAViewOrSharded(isAnySecondaryNamespaceAViewOrSharded) {
auto catalog = CollectionCatalog::get(opCtx);
for (const auto& secondaryNssOrUuid : secondaryExecNssList) {
auto secondaryNss = catalog->resolveNamespaceStringOrUUID(opCtx, secondaryNssOrUuid);
// Don't store a CollectionPtr if the main nss is also a secondary one.
if (secondaryNss != mainCollNss) {
// Even if the collection corresponding to 'secondaryNss' doesn't exist, we
// still want to include it. It is the responsibility of consumers of this class
// to verify that a collection exists before accessing it.
auto collPtr = catalog->lookupCollectionByNamespace(opCtx, secondaryNss);
_secondaryColls.emplace(std::move(secondaryNss), std::move(collPtr));
}
}
}
explicit MultipleCollectionAccessor(const CollectionPtr* mainColl) : _mainColl(mainColl) {}
explicit MultipleCollectionAccessor(const CollectionPtr& mainColl)
: MultipleCollectionAccessor(&mainColl) {}
bool hasMainCollection() const {
return _mainColl && _mainColl->get();
}
const CollectionPtr& getMainCollection() const {
return *_mainColl;
}
const std::map<NamespaceString, CollectionPtr>& getSecondaryCollections() const {
return _secondaryColls;
}
bool isAnySecondaryNamespaceAViewOrSharded() const {
return _isAnySecondaryNamespaceAViewOrSharded;
}
const CollectionPtr& lookupCollection(const NamespaceString& nss) const {
if (_mainColl && _mainColl->get() && nss == _mainColl->get()->ns()) {
return *_mainColl;
} else if (auto itr = _secondaryColls.find(nss); itr != _secondaryColls.end()) {
return itr->second;
}
return CollectionPtr::null;
}
void clear() {
_mainColl = &CollectionPtr::null;
_secondaryColls.clear();
}
void forEach(std::function<void(const CollectionPtr&)> func) const {
if (hasMainCollection()) {
func(getMainCollection());
}
for (const auto& [name, coll] : getSecondaryCollections()) {
if (coll) {
func(coll);
}
}
}
private:
const CollectionPtr* _mainColl{&CollectionPtr::null};
// Tracks whether any secondary namespace is a view or sharded based on information captured
// at the time of lock acquisition. This is used to determine if a $lookup is eligible for
// pushdown into the query execution subsystem as $lookup against a foreign view or a foreign
// sharded collection is not currently supported by the execution subsystem.
bool _isAnySecondaryNamespaceAViewOrSharded = false;
// Map from namespace to a corresponding CollectionPtr.
std::map<NamespaceString, CollectionPtr> _secondaryColls{};
};
} // namespace mongo
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