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https://issues.apache.org/jira/browse/PIG-3082?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13785427#comment-13785427
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Julien Le Dem commented on PIG-3082:
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This is intended.
The second behavior described above is really problematic.
If a UDF breaks because it returns a schema of more than one field it should be
changed to return one field of type tuple.
Once fixed it works in all versions of Pig.
This is only removing an unsafe use of outputSchema in favor of the existing
correct use.
> outputSchema of a UDF allows two usages when describing a Tuple schema
> ----------------------------------------------------------------------
>
> Key: PIG-3082
> URL: https://issues.apache.org/jira/browse/PIG-3082
> Project: Pig
> Issue Type: Bug
> Reporter: Julien Le Dem
> Assignee: Jonathan Coveney
> Fix For: 0.12.0
>
> Attachments: PIG-3082-0.patch, PIG-3082-1.patch
>
>
> When defining an evalfunc that returns a Tuple there are two ways you can
> implement outputSchema().
> - The right way: return a schema that contains one Field that contains the
> type and schema of the return type of the UDF
> - The unreliable way: return a schema that contains more than one field and
> it will be understood as a tuple schema even though there is no type (which
> is in Field class) to specify that. This is particularly deceitful when the
> output schema is derived from the input schema and the outputted Tuple
> sometimes contain only one field. In such cases Pig understands the output
> schema as a tuple only if there is more than one field. And sometimes it
> works, sometimes it does not.
> We should at least issue a warning (backward compatibility) if not plain
> throw an exception when the output schema contains more than one Field.
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