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https://issues.apache.org/jira/browse/PIG-3568?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13820823#comment-13820823
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Daniel Dai commented on PIG-3568:
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Agree with #1. For #2, seems that's not the intention for the current code.
Though we can see it in POPackage, but the code path is not in use. But since
we plan to clean up STATUS_NULL -> (null, STATUS_OK), we are free to redefine
the meaning for STATUS_NULL (a different name might be better).
> Define the semantics of POStatus.STATUS_NULL
> --------------------------------------------
>
> Key: PIG-3568
> URL: https://issues.apache.org/jira/browse/PIG-3568
> Project: Pig
> Issue Type: Bug
> Reporter: Mark Wagner
> Assignee: Mark Wagner
>
> The meaning of POStatus.STATUS_NULL is not well documented and there are
> conflicting view points on its interpretation. The two interpretations are:
> 1. POStatus.STATUS_NULL indicates that the pulled output IS null. This is
> mostly found in expression operators, particularly comparison operators.
> 2. POStatus.STATUS_NULL indicates that the pull did not produce any output.
> This is backed up by its usage in POPackage (not JoinPackage) for flattening
> an empty bag, and PigGenericMapBase where pulls on the operator pipeline that
> result in STATUS_NULL are discarded.
> I propose that 2 should be the official definition going forward. The first
> meaning is easily indicated by (null, STATUS_OK) and all the relational
> operators already seem to follow 2. I'd like to hear others' opinions as well
> though.
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