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Posted to derby-dev@db.apache.org by "Kim Haase (JIRA)" <ji...@apache.org> on 2013/09/12 17:22:53 UTC
[jira] [Updated] (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 updated DERBY-6127:
-----------------------------
Attachment: DERBY-6127.zip
DERBY-6127.stat
DERBY-6127.diff
Thanks, Rick. Attaching DERBY-6127.diff, DERBY-6127.stat, and DERBY-6127.zip, with changes to the following:
M src/ref/rrefsqljcreateaggregate.dita
M src/devguide/cdevspecialuda.dita
Thanks in advance for your feedback.
> 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
> 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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