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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/db/pipeline/document_source_out.h"
#include "mongo/util/destructor_guard.h"
namespace mongo {
/**
* Version of $out which directs writes to a temporary collection, then renames the temp collection
* to the target collection with the 'dropTarget' option set to true.
*/
class DocumentSourceOutReplaceColl final : public DocumentSourceOut {
public:
using DocumentSourceOut::DocumentSourceOut;
~DocumentSourceOutReplaceColl() {
DESTRUCTOR_GUARD(
// Make sure we drop the temp collection if anything goes wrong. Errors are ignored
// here because nothing can be done about them. Additionally, if this fails and the
// collection is left behind, it will be cleaned up next time the server is started.
if (_tempNs.size()) {
LocalReadConcernBlock readLocal(pExpCtx->opCtx);
pExpCtx->mongoProcessInterface->directClient()->dropCollection(_tempNs.ns());
});
}
/**
* Sets up a temp collection which contains the same indexes and options as the output
* collection. All writes will be directed to the temp collection.
*/
void initializeWriteNs() final;
/**
* Renames the temp collection to the output collection with the 'dropTarget' option set to
* true.
*/
void finalize() final;
const NamespaceString& getWriteNs() const final {
return _tempNs;
};
private:
// Holds on to the original collection options and index specs so we can check they didn't
// change during computation.
BSONObj _originalOutOptions;
std::list<BSONObj> _originalIndexes;
// The temporary namespace for the $out writes.
NamespaceString _tempNs;
};
} // namespace mongo
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