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https://issues.apache.org/jira/browse/PIG-3368?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Koji Noguchi resolved PIG-3368.
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Resolution: Duplicate
Assignee: (was: Aniket Mokashi)
Fix Version/s: (was: 0.18.0)
Let's track this in PIG-5201.
> doc pig flatten operator applied to empty vs null bag
> -----------------------------------------------------
>
> Key: PIG-3368
> URL: https://issues.apache.org/jira/browse/PIG-3368
> Project: Pig
> Issue Type: Improvement
> Components: documentation
> Reporter: Andy Schlaikjer
>
> [Pig docs|http://pig.apache.org/docs/r0.11.0/basic.html#flatten] state that
> FLATTEN(field_of_type_bag) may generate a cross-product in the case when an
> additional field is projected, e.g.:
> y = FOREACH x GENERATE f1, FLATTEN(fbag) as f2;
> Additionally, for records in x for which fbag is empty (not null), no output
> record is generated.
> What is expected behavior when fbag is null?
> Some users might expect similar behavior, but FLATTEN actually passes through
> the null, resulting in an output record (f1, f2) where f2 is null.
> It would be useful to update FLATTEN docs to mention this.
> http://svn.apache.org/viewvc/pig/trunk/src/docs/src/documentation/content/xdocs/basic.xml?view=markup#l5051
> I'm guessing these are the relevant bits which affect this behavior:
> http://svn.apache.org/viewvc/pig/trunk/src/org/apache/pig/backend/hadoop/executionengine/physicalLayer/relationalOperators/POForEach.java?view=markup#l440
> http://svn.apache.org/viewvc/pig/trunk/src/org/apache/pig/backend/hadoop/executionengine/physicalLayer/relationalOperators/POForEach.java?view=markup#l468
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