[
https://issues.apache.org/jira/browse/DERBY-672?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13031306#comment-13031306
]
Rick Hillegas commented on DERBY-672:
-------------------------------------
The SQL Server syntax for user-defined aggregates can be found here:
http://msdn.microsoft.com/en-us/library/ms182741.aspx and
http://msdn.microsoft.com/en-us/library/ms131051.aspx In summary, you bind an
external class to an aggregate name. The class must satisfy a contract, which
requires it to have methods to initialize, aggregate, merge, and terminate:
CREATE AGGREGATE [<schemaName>.]<aggregateName> ( <functionParameter> [,
<functionParameter> ] * )
RETURNS <returnDataType>
EXTERNAL NAME <className>
where <functionParameter> is as defined for CREATE FUNCTION (a parameter name
followed by a dataType)
and <className> implements the following methods:
public void init();
public void accumulate( <methodParameter> [, <methodParameter> ] *); // method
parameters correspond to function parameters above
public void merge( <className> otherAggregator );
public <returnType> terminate(); // returnType corresponds to returnDataType
above
> 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.
--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira
