[GitHub] xbaran commented on a change in pull request #526: HIVE-21218: KafkaSerDe doesn't support topics created via Confluent

[GitBox <gi...@apache.org>]

xbaran commented on a change in pull request #526: HIVE-21218: KafkaSerDe doesn't support topics created via Confluent
URL: https://github.com/apache/hive/pull/526#discussion_r254981251
 
 

 ##########
 File path: kafka-handler/src/java/org/apache/hadoop/hive/kafka/KafkaSerDe.java
 ##########
 @@ -369,6 +379,20 @@ private SubStructObjectInspector(StructObjectInspector baseOI, int toIndex) {
     }
   }
 
+  static class ConfluentAvroBytesConverter extends AvroBytesConverter {
+    ConfluentAvroBytesConverter(Schema schema) {
+      super(schema);
+    }
+
+    @Override
+    Decoder getDecoder(byte[] value) {
+      /**
+       * Confluent 4 magic bytes that represents Schema ID as Integer. These bits are added before value bytes.
+       */
+      return DecoderFactory.get().binaryDecoder(value, 5, value.length - 5, null);
 
 Review comment:
   The problem is you have to provide schema during `initialize` and there is no record to read schema ID from at that time. I was thinking about switch `bytesConverter` to a function/supplier or factory and give it to the KafkaWritable and resolve byteconverter lazy way. However I'm quite new to Hive and need to deep more to mechanics how the low level api works. I'd like to see hive download schemas from schema registry, but I need to think about concept first.
   
   About the compatibility, there are several compatibility modes in schema registry. It can be set for each topic and you can set BACKWARD compat for example.
   
   And yea you can have objects with literally different schemas not just different versions in one topic and I think this problem Hive cannot address.

----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on GitHub and use the
URL above to go to the specific comment.
 
For queries about this service, please contact Infrastructure at:
users@infra.apache.org


With regards,
Apache Git Services