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https://issues.apache.org/jira/browse/FLINK-10049?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16812935#comment-16812935
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Hequn Cheng commented on FLINK-10049:
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[~xccui] Thanks for opening the issue. Good catch and +1 to unify the
processing logic.
This is an interesting topic and I would like to share some thoughts too. I
think it's a big topic for the improvement of UDF which deserves a discussion
by itself.
As for the null input problem raised by this issue, I have come up with two
problems to be addressed.
- How to handle Exceptions for UDF.
We may need a global configuration to control the behavior of handling
exceptions for UDF. For example, providing a return null option.
- How to handle NULL input and NULL output.
We can let the UDF process null input by default. However, we can also provide
options like SqlServer, i.e., {{RETURNS NULL ON NULL INPUT}}, return NULL when
any of the arguments it receives is NULL, without actually invoking the body of
the function.
What do you guys think?
> Unify the processing logic for NULL arguments in SQL built-in functions
> -----------------------------------------------------------------------
>
> Key: FLINK-10049
> URL: https://issues.apache.org/jira/browse/FLINK-10049
> Project: Flink
> Issue Type: Improvement
> Components: Table SQL / API
> Reporter: Xingcan Cui
> Assignee: vinoyang
> Priority: Major
>
> Currently, the built-in functions treat NULL arguments in different ways.
> E.g., ABS(NULL) returns NULL, while LOG10(NULL) throws an NPE. The general
> SQL-way of handling NULL values should be that if one argument is NULL the
> result is NULL. We should unify the processing logic for that.
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