Pradeep Kamath commented on PIG-930:

Not sure why jira shows part of above comment striked out - I meant the entire 
text to be part of the comment.

> 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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