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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/exec/pipeline_proxy.h"
namespace mongo {
/**
* ChangeStreamProxyStage is a drop-in replacement for PipelineProxyStage, intended to manage the
* serialization of change stream pipeline output from Document to BSON. In particular, it is
* additionally responsible for tracking the latestOplogTimestamps and postBatchResumeTokens that
* are necessary for correct merging on mongoS and, in the latter case, must also be provided to
* mongoD clients.
*/
class ChangeStreamProxyStage final : public PipelineProxyStage {
public:
static const char* kStageType;
/**
* The 'pipeline' argument must be a $changeStream pipeline. Passing a non-$changeStream into
* the constructor will cause an invariant() to fail.
*/
ChangeStreamProxyStage(OperationContext* opCtx,
std::unique_ptr<Pipeline, PipelineDeleter> pipeline,
WorkingSet* ws);
/**
* Returns an empty PlanStageStats object.
*/
std::unique_ptr<PlanStageStats> getStats() final;
/**
* Passes through the latest oplog timestamp from the proxied pipeline. We only expose the oplog
* timestamp in the event that we need to merge on mongoS.
*/
Timestamp getLatestOplogTimestamp() const {
return _includeMetaData ? _latestOplogTimestamp : Timestamp();
}
/**
* Passes through the most recent resume token from the proxied pipeline.
*/
BSONObj getPostBatchResumeToken() const {
return _postBatchResumeToken;
}
StageType stageType() const final {
return STAGE_CHANGE_STREAM_PROXY;
}
protected:
boost::optional<Document> getNext() final;
private:
/**
* Verifies that the docs's resume token has not been modified.
*/
void _validateResumeToken(const Document& event) const;
/**
* Set the speculative majority read timestamp if we have scanned up to a certain oplog
* timestamp.
*/
void _setSpeculativeReadTimestamp();
Timestamp _latestOplogTimestamp;
BSONObj _postBatchResumeToken;
};
} // namespace mongo
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