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/**
* Copyright (C) 2017 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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.
*
* Uses the ExpressionContext to determine what collection to look up into.
* TODO SERVER-29134 When we allow change streams on multiple collections, this will need to change.
*/
class DocumentSourceLookupChangePostImage final : public DocumentSourceNeedsMongod {
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() const final {
StageConstraints constraints(StreamType::kStreaming,
PositionRequirement::kNone,
HostTypeRequirement::kAnyShard,
DiskUseRequirement::kNoDiskUse,
FacetRequirement::kNotAllowed);
constraints.canSwapWithMatch = true;
return constraints;
}
GetDepsReturn 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 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)
: DocumentSourceNeedsMongod(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.
*/
NamespaceString assertNamespaceMatches(const Document& inputDoc) const;
};
} // namespace mongo
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