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/**
* Copyright (C) 2023-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 <queue>
#include "mongo/db/exec/document_value/document.h"
namespace mongo {
namespace change_stream_split_event {
constexpr auto kIdField = "_id"_sd;
constexpr auto kSplitEventField = "splitEvent"_sd;
constexpr auto kFragmentNumberField = "fragment"_sd;
constexpr auto kTotalFragmentsField = "of"_sd;
/**
* Calculates BSON size by serializing the event to BSON. Ensures that the serialization is
* re-usable. The parameter 'withMetadata' desides whether the metadata is counted.
* Also returns a new document optimized for later serialization by PlanExecutorPipeline.
*/
std::pair<Document, size_t> processChangeEventBeforeSplit(const Document& event, bool withMetadata);
/**
* Splits the given change stream 'event' to several sub-events, called fragments. The size of BSON
* serialization of each fragment does not exceed the given maximum fragment size. Each fragment
* carries additionally fragment's ordinal number and the total number of fragments. Each fragment
* has its own resume token as its '_id' and the sort key. In the resume scenario, the
* 'skipFirstFragments' parameter indicates how many fragments were already received by the client
* and can be skipped. For example, the following change event
* {_id: "RESUMETOKEN1", fullDocument: ..., fullDocumentBeforeChange: ..., ...}
* can be split into the following fragments
* {_id: "RESUMETOKEN2", splitEvent{fragment: 1, of: 2}, fullDocumentBeforeChange: ...}
* {_id: "RESUMETOKEN3", splitEvent{fragment: 2, of: 2}, fullDocument: ...}
*/
std::queue<Document> splitChangeEvent(const Document& event,
size_t maxFragmentBsonSize,
size_t skipFirstFragments = 0);
} // namespace change_stream_split_event
} // namespace mongo
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