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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-672) Re-enable user defined aggregates
Date Wed, 18 Jul 2012 15:32:36 GMT

    [ https://issues.apache.org/jira/browse/DERBY-672?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13417176#comment-13417176
] 

Rick Hillegas commented on DERBY-672:
-------------------------------------

Thanks for continuing the discussion, Knut. I like your suggestion for how to eliminate the
need to cast inside the merge() method. I agree that it makes the Aggregator interface iself
a little more wordy, but I don't have a better idea.

I hope that users will be able to re-use an Aggregator for multiple datatypes as shown in
your first example:

  create derby aggregate int_sum for int returns int external name 'MySum<Integer>';
  create derby aggregate bigint_sum for bigint returns bigint external name 'MySum<Long>';

I suppose it depends on whether Derby can currently swallow a genericized class name and,
if not, how hard it would be to teach Derby this trick. We may need to get further into implementation
before we can answer your question. Thanks.
                
> Re-enable user defined aggregates
> ---------------------------------
>
>                 Key: DERBY-672
>                 URL: https://issues.apache.org/jira/browse/DERBY-672
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>            Reporter: Rick Hillegas
>
> Nicolas Dufour in an email thread titled "functions and list" started on November 2,
2005 requests the ability to create user defined aggregates.
> This functionality used to be in Cloudscape. It was disabled presumably because it was
considered non-standard. However, most of the machinery needed for this feature is still in
the code. We should re-enable user defined aggregates after we agree on acceptable syntax.

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