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/**
* Copyright (C) 2021-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_change_stream.h"
namespace mongo {
/**
* A custom subclass of DocumentSourceMatch which is used to generate a $match stage to be applied
* on the oplog. The stage requires itself to be the first stage in the pipeline.
*/
class DocumentSourceChangeStreamOplogMatch final : public DocumentSourceMatch {
public:
static constexpr StringData kStageName = "$_internalChangeStreamOplogMatch"_sd;
DocumentSourceChangeStreamOplogMatch(Timestamp clusterTime,
const boost::intrusive_ptr<ExpressionContext>& expCtx);
DocumentSourceChangeStreamOplogMatch(const DocumentSourceChangeStreamOplogMatch& other,
const boost::intrusive_ptr<ExpressionContext>& newExpCtx)
: DocumentSourceMatch(other, newExpCtx) {
_clusterTime = other._clusterTime;
_optimizedEndOfPipeline = other._optimizedEndOfPipeline;
}
boost::intrusive_ptr<DocumentSource> clone(
const boost::intrusive_ptr<ExpressionContext>& newExpCtx) const final {
return new DocumentSourceChangeStreamOplogMatch(*this, newExpCtx);
}
static boost::intrusive_ptr<DocumentSource> createFromBson(
BSONElement elem, const boost::intrusive_ptr<ExpressionContext>& pExpCtx);
static boost::intrusive_ptr<DocumentSourceChangeStreamOplogMatch> create(
const boost::intrusive_ptr<ExpressionContext>& expCtx,
const DocumentSourceChangeStreamSpec& spec);
const char* getSourceName() const final;
GetNextResult doGetNext() final {
// We should never execute this stage directly. We expect this stage to be absorbed into the
// cursor feeding the pipeline, and executing this stage may result in the use of the wrong
// collation. The comparisons against the oplog must use the simple collation, regardless of
// the collation on the ExpressionContext.
MONGO_UNREACHABLE;
}
StageConstraints constraints(Pipeline::SplitState pipeState) const final;
Value serialize(SerializationOptions opts = SerializationOptions()) const final override;
protected:
Pipeline::SourceContainer::iterator doOptimizeAt(Pipeline::SourceContainer::iterator itr,
Pipeline::SourceContainer* container) final;
private:
/**
* This constructor is only used for deserializing from BSON, in which case there is no value
* for the '_clusterTime' field. We leave this field as boost::none and assume that it will not
* be needed. We also assume that optimizations have have already been applied.
*/
DocumentSourceChangeStreamOplogMatch(BSONObj filter,
const boost::intrusive_ptr<ExpressionContext>& expCtx)
: DocumentSourceMatch(std::move(filter), expCtx), _optimizedEndOfPipeline(true) {
expCtx->tailableMode = TailableModeEnum::kTailableAndAwaitData;
}
// Needed for re-creating the filter during optimization. Note that we do not serialize these
// fields. The filter in a serialized DocumentSourceOplogMatch is considered final, so there is
// no need to re-create it.
boost::optional<Timestamp> _clusterTime;
// Used to avoid infinte optimization loops. Note that we do not serialize this field, because
// we assume that DocumentSourceOplogMatch is always serialized after optimization.
bool _optimizedEndOfPipeline = false;
};
} // namespace mongo
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