[jira] [Commented] (PIG-5277) Spark mode is writing nulls among tuples to the output

["Rohini Palaniswamy (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PIG-5277?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16112199#comment-16112199 ] 

Rohini Palaniswamy commented on PIG-5277:
-----------------------------------------

Not a Spark expert. So do not have any suggestions. 

If 3 or 4 is not possible, I would rather prefer approach 2. It is better to avoid writing garbage into file than try and skip while reading.

> Spark mode is writing nulls among tuples to the output 
> -------------------------------------------------------
>
>                 Key: PIG-5277
>                 URL: https://issues.apache.org/jira/browse/PIG-5277
>             Project: Pig
>          Issue Type: Bug
>          Components: spark
>            Reporter: Adam Szita
>            Assignee: Adam Szita
>
> After committing PIG-3655 a couple of Spark mode tests (e.g. org.apache.pig.test.TestEvalPipeline.testCogroupAfterDistinct) started failing on:
> {code}
> java.lang.Error: java.io.IOException: Corrupt data file, expected tuple type byte, but seen 27
> 	at org.apache.pig.backend.hadoop.executionengine.HJob$1.hasNext(HJob.java:122)
> 	at org.apache.pig.test.TestEvalPipeline.testCogroupAfterDistinct(TestEvalPipeline.java:1052)
> Caused by: java.io.IOException: Corrupt data file, expected tuple type byte, but seen 27
> 	at org.apache.pig.impl.io.InterRecordReader.readDataOrEOF(InterRecordReader.java:158)
> 	at org.apache.pig.impl.io.InterRecordReader.nextKeyValue(InterRecordReader.java:194)
> 	at org.apache.pig.impl.io.InterStorage.getNext(InterStorage.java:79)
> 	at org.apache.pig.impl.io.ReadToEndLoader.getNextHelper(ReadToEndLoader.java:238)
> 	at org.apache.pig.impl.io.ReadToEndLoader.getNext(ReadToEndLoader.java:218)
> 	at org.apache.pig.backend.hadoop.executionengine.HJob$1.hasNext(HJob.java:115)
> {code}
> This is because InterRecordReader became much stricter after PIG-3655. Before it just simply skipped these bytes thinking that they are just garbage on the split beginning. Now when we expect a [proper tuple with a tuple type byte|https://github.com/apache/pig/blob/trunk/src/org/apache/pig/impl/io/InterRecordReader.java#L153] we see these nulls and throw an Exception.
> As I can see it this is happening because JoinGroupSparkConverter has to return something even when it shouldn't.
> When the POPackage operator returns a [POStatus.STATUS_NULL|https://github.com/apache/pig/blob/trunk/src/org/apache/pig/backend/hadoop/executionengine/spark/converter/JoinGroupSparkConverter.java#L211], the converter shouldn't return a thing, but it can't do better than returning a null. This then gets written out by Spark..



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