SERVER-58060 Add new internal FindAndModifyImageLookup aggregation stage

1 files changed, 83 insertions, 0 deletions

diff --git a/src/mongo/db/pipeline/document_source_find_and_modify_image_lookup.h b/src/mongo/db/pipeline/document_source_find_and_modify_image_lookup.h
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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.h"
+
+namespace mongo {
+
+/**
+ * This stage will take a list of oplog entries as input and forge a no-op pre- or post-image to be
+ * returned before each 'findAndModify' oplog entry that has the 'needsRetryImage' field. This stage
+ * also downconverts 'findAndModify' entries by stripping the 'needsRetryImage' field and appending
+ * the appropriate 'preImageOpTime' or 'postImageOpTime' field.
+ */
+class DocumentSourceFindAndModifyImageLookup : public DocumentSource {
+public:
+    static constexpr StringData kStageName = "$_internalFindAndModifyImageLookup"_sd;
+
+    static boost::intrusive_ptr<DocumentSourceFindAndModifyImageLookup> create(
+        const boost::intrusive_ptr<ExpressionContext>&);
+
+    static boost::intrusive_ptr<DocumentSourceFindAndModifyImageLookup> createFromBson(
+        const BSONElement elem, const boost::intrusive_ptr<ExpressionContext>& expCtx);
+
+    DepsTracker::State getDependencies(DepsTracker* deps) const final;
+
+    DocumentSource::GetModPathsReturn getModifiedPaths() const final;
+
+    Value serialize(boost::optional<ExplainOptions::Verbosity> explain) const;
+
+    StageConstraints constraints(Pipeline::SplitState pipeState) const final;
+
+    boost::optional<DistributedPlanLogic> distributedPlanLogic() final {
+        return boost::none;
+    }
+
+    const char* getSourceName() const {
+        return DocumentSourceFindAndModifyImageLookup::kStageName.rawData();
+    }
+
+protected:
+    DocumentSource::GetNextResult doGetNext() override;
+
+private:
+    DocumentSourceFindAndModifyImageLookup(const boost::intrusive_ptr<ExpressionContext>& expCtx);
+
+    // Forges the no-op pre- or post-image document to be returned. Also downconverts the original
+    // 'findAndModify' oplog entry and stashes it.
+    boost::optional<Document> _forgeNoopImageDoc(Document inputDoc, OperationContext* opCtx);
+
+    // Represents the stashed 'findAndModify' document. This indicates that the previous document
+    // emitted was a forged pre- or post-image.
+    boost::optional<Document> _stashedFindAndModifyDoc;
+};
+
+}  // namespace mongo