[jira] [Commented] (HIVE-4329) HCatalog should use getHiveRecordWriter rather than getRecordWriter

["David Chen (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-4329?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13999308#comment-13999308 ] 

David Chen commented on HIVE-4329:
----------------------------------

If I understand correctly, it seems that this change will end up being quite extensive. HCatalog is currently using {{org.apache.hadoop.mapred.OutputFormat}} everywhere. It seems that in order to have HCatalog properly use Hive's write facilities, we would have to change HCatalog to use HiveOutputFormat rathjer than the Hadoop OutputFormat.

> HCatalog should use getHiveRecordWriter rather than getRecordWriter
> -------------------------------------------------------------------
>
>                 Key: HIVE-4329
>                 URL: https://issues.apache.org/jira/browse/HIVE-4329
>             Project: Hive
>          Issue Type: Bug
>          Components: HCatalog, Serializers/Deserializers
>    Affects Versions: 0.10.0
>         Environment: discovered in Pig, but it looks like the root cause impacts all non-Hive users
>            Reporter: Sean Busbey
>            Assignee: David Chen
>
> Attempting to write to a HCatalog defined table backed by the AvroSerde fails with the following stacktrace:
> {code}
> java.lang.ClassCastException: org.apache.hadoop.io.NullWritable cannot be cast to org.apache.hadoop.io.LongWritable
> 	at org.apache.hadoop.hive.ql.io.avro.AvroContainerOutputFormat$1.write(AvroContainerOutputFormat.java:84)
> 	at org.apache.hcatalog.mapreduce.FileRecordWriterContainer.write(FileRecordWriterContainer.java:253)
> 	at org.apache.hcatalog.mapreduce.FileRecordWriterContainer.write(FileRecordWriterContainer.java:53)
> 	at org.apache.hcatalog.pig.HCatBaseStorer.putNext(HCatBaseStorer.java:242)
> 	at org.apache.hcatalog.pig.HCatStorer.putNext(HCatStorer.java:52)
> 	at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigOutputFormat$PigRecordWriter.write(PigOutputFormat.java:139)
> 	at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigOutputFormat$PigRecordWriter.write(PigOutputFormat.java:98)
> 	at org.apache.hadoop.mapred.MapTask$NewDirectOutputCollector.write(MapTask.java:559)
> 	at org.apache.hadoop.mapreduce.task.TaskInputOutputContextImpl.write(TaskInputOutputContextImpl.java:85)
> {code}
> The proximal cause of this failure is that the AvroContainerOutputFormat's signature mandates a LongWritable key and HCat's FileRecordWriterContainer forces a NullWritable. I'm not sure of a general fix, other than redefining HiveOutputFormat to mandate a WritableComparable.
> It looks like accepting WritableComparable is what's done in the other Hive OutputFormats, and there's no reason AvroContainerOutputFormat couldn't also be changed, since it's ignoring the key. That way fixing things so FileRecordWriterContainer can always use NullWritable could get spun into a different issue?
> The underlying cause for failure to write to AvroSerde tables is that AvroContainerOutputFormat doesn't meaningfully implement getRecordWriter, so fixing the above will just push the failure into the placeholder RecordWriter.



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