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https://issues.apache.org/jira/browse/CASSANDRA-8374?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14253315#comment-14253315
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Robert Stupp commented on CASSANDRA-8374:
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Convinces me - so now +1 on {{RETURNS NULL ON NULL INPUT}} as the default.
But I'm not sold on the *term* {{RETURNS NULL ON NULL INPUT}} because such UDA
state functions must not be used on {{null}} input at all (and the state must
not change). Otherwise it would assume {{null}} as the return value, using
{{null}} as the new state, meaning that the state function would never be
called again. That would mean that such a UDA would always return {{null}} if
just one row (out of many) has a {{null}} value.
So I propose just to rename {{ALLOW NULLS}} to {{CALLED ON NULL INPUT}} and not
add {{RETURNS NULL ON NULL INPUT}} to CQL syntax.
> Better support of null for UDF
> ------------------------------
>
> Key: CASSANDRA-8374
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8374
> Project: Cassandra
> Issue Type: Bug
> Reporter: Sylvain Lebresne
> Assignee: Robert Stupp
> Fix For: 3.0
>
> Attachments: 8473-1.txt, 8473-2.txt
>
>
> Currently, every function needs to deal with it's argument potentially being
> {{null}}. There is very many case where that's just annoying, users should be
> able to define a function like:
> {noformat}
> CREATE FUNCTION addTwo(val int) RETURNS int LANGUAGE JAVA AS 'return val + 2;'
> {noformat}
> without having this crashing as soon as a column it's applied to doesn't a
> value for some rows (I'll note that this definition apparently cannot be
> compiled currently, which should be looked into).
> In fact, I think that by default methods shouldn't have to care about
> {{null}} values: if the value is {{null}}, we should not call the method at
> all and return {{null}}. There is still methods that may explicitely want to
> handle {{null}} (to return a default value for instance), so maybe we can add
> an {{ALLOW NULLS}} to the creation syntax.
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