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Posted to derby-dev@db.apache.org by "Kim Haase (JIRA)" <ji...@apache.org> on 2013/09/13 00:24:52 UTC

[jira] [Resolved] (DERBY-6127) Tell users to make sure that the state of a user-defined aggregate needs to be serializable

     [ https://issues.apache.org/jira/browse/DERBY-6127?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Kim Haase resolved DERBY-6127.
------------------------------

          Resolution: Fixed
       Fix Version/s: 10.11.0.0
                      10.10.1.3
    Issue & fix info:   (was: Patch Available)

Thanks again, Rick.

Committed patch DERBY-6127.diff to documentation trunk at revision 1522740. 

Merged to 10.10 doc branch at revision 1522744.
                
> Tell users to make sure that the state of a user-defined aggregate needs to be serializable
> -------------------------------------------------------------------------------------------
>
>                 Key: DERBY-6127
>                 URL: https://issues.apache.org/jira/browse/DERBY-6127
>             Project: Derby
>          Issue Type: Improvement
>          Components: Documentation
>    Affects Versions: 10.10.1.1
>            Reporter: Rick Hillegas
>            Assignee: Kim Haase
>             Fix For: 10.10.1.3, 10.11.0.0
>
>         Attachments: DERBY-6127.diff, DERBY-6127.stat, DERBY-6127.zip
>
>
> The Reference Manual section on "CREATE DERBY AGGREGATE statement" should tell users to make sure that all of the state of their user-defined aggregate is really serializable. This is because the Aggregator interface extends java.io.Serializable. A user-defined aggregate may end up being serialized to disk when performing grouped aggregation over a large number of groups. That is, intermediate results may be serialized to disk for a query like the following. The serialization will fail if the user-defined aggregate contains non-serializable fields:
>   select a, myAggregate( b ) from myTable group by a

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