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Pig >> mail # dev >> POStatus.STATUS_NULL Semantics

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POStatus.STATUS_NULL Semantics
Hi Devs,

While discussing the Pig on Tez project today, we were unable to reach
a conclusion on what the semantics of what POStatus.STATUS_NULL are
and would like to ask those who remember the history of Pig to chime
in. The two interpretations are:

1. POStatus.STATUS_NULL indicates that the pulled output IS null. This
is used in some places like EqualToExpr.

2. POStatus.STATUS_NULL indicates that the pull did not produce any
output. This is backed up by it's usage in POPackage for flattening an
empty bag, and PigGenericMapBase where pulls on the operator pipeline
that result in STATUS_NULL are discarded.

If nobody has any concrete documentation or explanation for the
discrepancy, I'll post a patch that makes the second option official
and changes all the examples of the first to return null with
STATUS_OK (this is what happens with the constant null currently).