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From "Robert Stupp (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8374) Better support of null for UDF
Date Fri, 19 Dec 2014 11:46:13 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8374?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14253315#comment-14253315
] 

Robert Stupp commented on CASSANDRA-8374:
-----------------------------------------

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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