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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.h"
#include "mongo/db/pipeline/document_source_change_stream.h"
namespace mongo {
/**
* Part of the change stream API machinery used to look up the post-image of a document. Uses the
* "documentKey" field of the input to look up the new version of the document.
*/
class DocumentSourceLookupChangePostImage final : public DocumentSource {
public:
static constexpr StringData kStageName = "$_internalLookupChangePostImage"_sd;
static constexpr StringData kFullDocumentFieldName =
DocumentSourceChangeStream::kFullDocumentField;
/**
* Creates a DocumentSourceLookupChangePostImage stage.
*/
static boost::intrusive_ptr<DocumentSourceLookupChangePostImage> create(
const boost::intrusive_ptr<ExpressionContext>& expCtx) {
return new DocumentSourceLookupChangePostImage(expCtx);
}
/**
* Only modifies a single path: "fullDocument".
*/
GetModPathsReturn getModifiedPaths() const final {
return {GetModPathsReturn::Type::kFiniteSet, {kFullDocumentFieldName.toString()}, {}};
}
StageConstraints constraints(Pipeline::SplitState pipeState) const final {
invariant(pipeState != Pipeline::SplitState::kSplitForShards);
StageConstraints constraints(StreamType::kStreaming,
PositionRequirement::kNone,
// If this is parsed on mongos it should stay on mongos. If
// we're not in a sharded cluster then it's okay to run on
// mongod.
HostTypeRequirement::kLocalOnly,
DiskUseRequirement::kNoDiskUse,
FacetRequirement::kNotAllowed,
TransactionRequirement::kNotAllowed,
ChangeStreamRequirement::kChangeStreamStage);
constraints.canSwapWithMatch = true;
return constraints;
}
boost::optional<MergingLogic> mergingLogic() final {
return boost::none;
}
DepsTracker::State getDependencies(DepsTracker* deps) const {
// The namespace is not technically needed yet, but we will if there is more than one
// collection involved.
deps->fields.insert(DocumentSourceChangeStream::kNamespaceField.toString());
deps->fields.insert(DocumentSourceChangeStream::kDocumentKeyField.toString());
deps->fields.insert(DocumentSourceChangeStream::kOperationTypeField.toString());
deps->fields.insert(DocumentSourceChangeStream::kIdField.toString());
// This stage does not restrict the output fields to a finite set, and has no impact on
// whether metadata is available or needed.
return DepsTracker::State::SEE_NEXT;
}
/**
* Performs the lookup to retrieve the full document.
*/
GetNextResult getNext() final;
Value serialize(boost::optional<ExplainOptions::Verbosity> explain = boost::none) const final {
if (explain) {
return Value{Document{{kStageName, Document()}}};
}
return Value(); // Do not serialize this stage unless we're explaining.
}
const char* getSourceName() const final {
return kStageName.rawData();
}
private:
DocumentSourceLookupChangePostImage(const boost::intrusive_ptr<ExpressionContext>& expCtx)
: DocumentSource(expCtx) {}
/**
* Uses the "documentKey" field from 'updateOp' to look up the current version of the document.
* Returns Value(BSONNULL) if the document couldn't be found.
*/
Value lookupPostImage(const Document& updateOp) const;
/**
* Throws a AssertionException if the namespace found in 'inputDoc' doesn't match the one on the
* ExpressionContext. If the namespace on the ExpressionContext is 'collectionless', then this
* function verifies that the only the database names match.
*/
NamespaceString assertValidNamespace(const Document& inputDoc) const;
};
} // namespace mongo
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