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https://issues.apache.org/jira/browse/PIG-930?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12748372#action_12748372
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Alan Gates commented on PIG-930:
--------------------------------

One question that seems worth asking is, is it right that the offset returned 
on bzip2 data cannot be properly bound to?  If possible it would seem better to 
correct this issue in the loader that is dealing with bzip2 data then forcing 
operators up in the pipeline to handle the fact that not all data formats will 
properly honor the bind position.

> merge join should handle compressed bz2 sorted files
> ----------------------------------------------------
>
>                 Key: PIG-930
>                 URL: https://issues.apache.org/jira/browse/PIG-930
>             Project: Pig
>          Issue Type: Bug
>            Reporter: Pradeep Kamath
>
> There are two issues - POLoad which is used to read the right side input does 
> not handle bz2 files right now. This needs to be fixed.
> Further inn the index map job we bindTo(startOfBlockOffSet) (this will 
> internally discard first tuple if offset > 0). Then we do the following:
> {noformat}
> While(tuple survives pipeline) {
>   Pos =  getPosition()
>   getNext() 
>   run the tuple  through pipeline in the right side which could have filter
> }
> Emit(key, pos, filename).
> {noformat}
>  
> Then in the map job which does the join, we bindTo(pos > 0 ? pos  1 : pos) 
> (we do pos -1 because bindTo will discard first tuple for pos> 0). Then we do 
> getNext()
> Now in bz2 compressed files, getPosition() returns a position which is not 
> really accurate. The problem is it could be a position in the middle of a 
> compressed bz2 block. Then when we use that position to bindTo() in the final 
> map job, the code would first hunt for a bz2 block header thus skipping the 
> whole current bz2 block. 

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