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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-672) Re-enable user defined aggregates
Date Wed, 18 Jul 2012 09:51:34 GMT

    [ https://issues.apache.org/jira/browse/DERBY-672?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13416965#comment-13416965
] 

Knut Anders Hatlen commented on DERBY-672:
------------------------------------------

The proposal doesn't say whether the class name argument itself could be a parameterized type.

That is, could we have

  public class MySum<T extends Number> implements Aggragator<T,T> { ... }

and then define aggregates for two different types using that single class

  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>';

?

Or would we have to define two separate sub-classes with fully specified types, like

  public class MyIntSum extends MySum<Integer> {}
  public class MyBigintSum extends MySum<Long> {}

  create derby aggregate int_sum for int returns int external name 'MyIntSum';
  create derby aggregate bigint_sum for bigint returns bigint external name 'MyBigintSum';

?
                
> 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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