SERVER-30506 Rename $changeNotification to $changeStream

1 files changed, 140 insertions, 0 deletions

diff --git a/src/mongo/db/pipeline/document_source_change_stream.h b/src/mongo/db/pipeline/document_source_change_stream.h
new file mode 100644
index 00000000000..a0e7a79c71d
--- /dev/null
+++ b/src/mongo/db/pipeline/document_source_change_stream.h
@@ -0,0 +1,140 @@
+/**
+ * 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_single_document_transformation.h"
+#include "mongo/db/pipeline/document_sources_gen.h"
+
+namespace mongo {
+
+/**
+ * The $changeStream stage is an alias for a cursor on oplog followed by a $match stage and a
+ * transform stage on mongod.
+ */
+class DocumentSourceChangeStream final {
+public:
+    class LiteParsed final : public LiteParsedDocumentSource {
+    public:
+        static std::unique_ptr<LiteParsed> parse(const AggregationRequest& request,
+                                                 const BSONElement& spec) {
+            return stdx::make_unique<LiteParsed>();
+        }
+
+        bool isChangeStream() const final {
+            return true;
+        }
+
+        stdx::unordered_set<NamespaceString> getInvolvedNamespaces() const final {
+            // TODO SERVER-29138: we need to communicate that this stage will need to look up
+            // documents from different collections.
+            return stdx::unordered_set<NamespaceString>();
+        }
+
+        // TODO SERVER-29138: Add required privileges.
+        PrivilegeVector requiredPrivileges(bool isMongos) const final {
+            return {};
+        }
+    };
+
+    class Transformation : public DocumentSourceSingleDocumentTransformation::TransformerInterface {
+    public:
+        Transformation(BSONObj changeStreamSpec) : _changeStreamSpec(changeStreamSpec.getOwned()) {}
+        ~Transformation() = default;
+        Document applyTransformation(const Document& input) final;
+        TransformerType getType() const final {
+            return TransformerType::kChangeStreamTransformation;
+        };
+        void optimize() final{};
+        Document serializeStageOptions(
+            boost::optional<ExplainOptions::Verbosity> explain) const final;
+        DocumentSource::GetDepsReturn addDependencies(DepsTracker* deps) const final;
+        DocumentSource::GetModPathsReturn getModifiedPaths() const final;
+
+    private:
+        BSONObj _changeStreamSpec;
+    };
+
+    // The name of the field where the document key (_id and shard key, if present) will be found
+    // after the transformation.
+    static constexpr StringData kDocumentKeyField = "documentKey"_sd;
+
+    // The name of the field where the full document will be found after the transformation. The
+    // full document is only present for certain types of operations, such as an insert.
+    static constexpr StringData kFullDocumentField = "fullDocument"_sd;
+
+    // The name of the field where the change identifier will be located after the transformation.
+    static constexpr StringData kIdField = "_id"_sd;
+
+    // The name of the field where the namespace of the change will be located after the
+    // transformation.
+    static constexpr StringData kNamespaceField = "ns"_sd;
+
+    // The name of the field where the type of the operation will be located after the
+    // transformation.
+    static constexpr StringData kOperationTypeField = "operationType"_sd;
+
+    // The name of this stage.
+    static constexpr StringData kStageName = "$changeStream"_sd;
+
+    // The name of the field where the timestamp of the change will be located after the
+    // transformation. The timestamp will be located inside the change identifier, so the full path
+    // to the timestamp will be kIdField + "." + kTimestampField.
+    static constexpr StringData kTimestmapField = "ts"_sd;
+
+    // The different types of operations we can use for the operation type.
+    static constexpr StringData kUpdateOpType = "update"_sd;
+    static constexpr StringData kDeleteOpType = "delete"_sd;
+    static constexpr StringData kReplaceOpType = "replace"_sd;
+    static constexpr StringData kInsertOpType = "insert"_sd;
+    static constexpr StringData kInvalidateOpType = "invalidate"_sd;
+
+    /**
+     * Produce the BSON object representing the filter for the $match stage to filter oplog entries
+     * to only those relevant for this $changeStream stage.
+     */
+    static BSONObj buildMatchFilter(const NamespaceString& nss, Timestamp startFrom, bool isResume);
+
+    /**
+     * Parses a $changeStream stage from 'elem' and produces the $match and transformation
+     * stages required.
+     */
+    static std::list<boost::intrusive_ptr<DocumentSource>> createFromBson(
+        BSONElement elem, const boost::intrusive_ptr<ExpressionContext>& expCtx);
+
+    static boost::intrusive_ptr<DocumentSource> createTransformationStage(
+        BSONObj changeStreamSpec, const boost::intrusive_ptr<ExpressionContext>& pExpCtx);
+
+private:
+    // It is illegal to construct a DocumentSourceChangeStream directly, use createFromBson()
+    // instead.
+    DocumentSourceChangeStream() = default;
+};
+
+}  // namespace mongo