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From "Pradeep Kamath (JIRA)" <j...@apache.org>
Subject [jira] Created: (PIG-930) merge join should handle compressed bz2 sorted files
Date Tue, 25 Aug 2009 01:31:59 GMT
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:

While(tuple survives pipeline) {

  Pos =  getPosition()


  run the tuple  through pipeline in the right side which could have filter


Emit(key, pos, filename).
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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