[GitHub] [beam] piotr-szuberski commented on a change in pull request #12838: [BEAM-10892] Add Proto support to Kafka Table Provider

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piotr-szuberski commented on a change in pull request #12838:
URL: https://github.com/apache/beam/pull/12838#discussion_r494409925



##########
File path: sdks/java/extensions/sql/src/main/java/org/apache/beam/sdk/extensions/sql/meta/provider/kafka/BeamKafkaProtoTable.java
##########
@@ -0,0 +1,114 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.beam.sdk.extensions.sql.meta.provider.kafka;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.List;
+import org.apache.beam.sdk.coders.RowCoder;
+import org.apache.beam.sdk.schemas.Schema;
+import org.apache.beam.sdk.transforms.DoFn;
+import org.apache.beam.sdk.transforms.PTransform;
+import org.apache.beam.sdk.transforms.ParDo;
+import org.apache.beam.sdk.values.KV;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.beam.sdk.values.Row;
+
+public class BeamKafkaProtoTable extends BeamKafkaTable {
+
+  public BeamKafkaProtoTable(Schema beamSchema, String bootstrapServers, List<String> topics) {
+    super(beamSchema, bootstrapServers, topics);
+  }
+
+  @Override
+  public PTransform<PCollection<KV<byte[], byte[]>>, PCollection<Row>> getPTransformForInput() {
+    return new ProtoRecorderDecoder(schema);
+  }
+
+  @Override
+  public PTransform<PCollection<Row>, PCollection<KV<byte[], byte[]>>> getPTransformForOutput() {
+    return new ProtoRecorderEncoder();
+  }
+
+  /** A PTransform to convert {@code KV<byte[], byte[]>} to {@link Row}. */
+  public static class ProtoRecorderDecoder
+      extends PTransform<PCollection<KV<byte[], byte[]>>, PCollection<Row>> {
+    private final Schema schema;
+
+    public ProtoRecorderDecoder(Schema schema) {
+      this.schema = schema;
+    }
+
+    @Override
+    public PCollection<Row> expand(PCollection<KV<byte[], byte[]>> input) {
+      return input
+          .apply(
+              "decodeProtoRecord",
+              ParDo.of(
+                  new DoFn<KV<byte[], byte[]>, Row>() {
+                    @ProcessElement
+                    public void processElement(ProcessContext c) {
+                      c.output(parseProtoPayloadToRow(c.element().getValue(), schema));
+                    }
+                  }))
+          .setRowSchema(schema);
+    }
+
+    static Row parseProtoPayloadToRow(byte[] payload, Schema payloadSchema) {
+      try {
+        InputStream inputStream = new ByteArrayInputStream(payload);
+        RowCoder rowCoder = RowCoder.of(payloadSchema);
+        return rowCoder.decode(inputStream);
+      } catch (IOException e) {
+        throw new IllegalArgumentException("Could not decode row from proto payload.", e);
+      }
+    }
+  }
+
+  /** A PTransform to convert {@link Row} to {@code KV<byte[], byte[]>}. */
+  public static class ProtoRecorderEncoder
+      extends PTransform<PCollection<Row>, PCollection<KV<byte[], byte[]>>> {
+
+    @Override
+    public PCollection<KV<byte[], byte[]>> expand(PCollection<Row> input) {
+      return input.apply(
+          "encodeProtoRecord",
+          ParDo.of(
+              new DoFn<Row, KV<byte[], byte[]>>() {
+                @ProcessElement
+                public void processElement(ProcessContext c) {
+                  Row in = c.element();
+                  c.output(KV.of(new byte[] {}, encodeRowToProtoBytes(in)));
+                }
+              }));
+    }
+
+    static byte[] encodeRowToProtoBytes(Row row) {
+      RowCoder rowCoder = RowCoder.of(row.getSchema());
+      ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
+      try {
+        rowCoder.encode(row, outputStream);

Review comment:
       Right, I've mistaken Row with RowProto. Thanks for the hints! I didn't know there is a universal coder for protos, I'll take a look.




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