SERVER-54676 Serialization and deserialization for shard-side change streams stages

1 files changed, 81 insertions, 0 deletions

diff --git a/src/mongo/db/pipeline/document_source_change_stream_oplog_match.h b/src/mongo/db/pipeline/document_source_change_stream_oplog_match.h
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+++ b/src/mongo/db/pipeline/document_source_change_stream_oplog_match.h
@@ -0,0 +1,81 @@
+/**
+ *    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 $match stage to be applied
+ * on the oplog. The stage requires itself to be the first stage in the pipeline.
+ */
+class DocumentSourceOplogMatch final : public DocumentSourceMatch,
+                                       public ChangeStreamStageSerializationInterface {
+public:
+    static constexpr StringData kStageName = "$_internalChangeStreamOplogMatch"_sd;
+
+    DocumentSourceOplogMatch(BSONObj filter, const boost::intrusive_ptr<ExpressionContext>& expCtx)
+        : DocumentSourceMatch(std::move(filter), expCtx) {
+        // A change stream pipeline should always create a tailable + awaitData cursor.
+        expCtx->tailableMode = TailableModeEnum::kTailableAndAwaitData;
+    }
+
+    DocumentSourceOplogMatch(const DocumentSourceOplogMatch& other) : DocumentSourceMatch(other) {}
+
+    virtual boost::intrusive_ptr<DocumentSourceMatch> clone() const {
+        return make_intrusive<std::decay_t<decltype(*this)>>(*this);
+    }
+
+    static boost::intrusive_ptr<DocumentSource> createFromBson(
+        BSONElement elem, const boost::intrusive_ptr<ExpressionContext>& pExpCtx);
+    static boost::intrusive_ptr<DocumentSourceOplogMatch> create(
+        const boost::intrusive_ptr<ExpressionContext>& expCtx, bool showMigrationEvents);
+
+    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(boost::optional<ExplainOptions::Verbosity> explain) const final {
+        return ChangeStreamStageSerializationInterface::serializeToValue(explain);
+    }
+
+private:
+    Value serializeLegacy(boost::optional<ExplainOptions::Verbosity> explain) const final;
+    Value serializeLatest(boost::optional<ExplainOptions::Verbosity> explain) const final;
+};
+}  // namespace mongo