Rick Hillegas created DERBY-6127:
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Summary: 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
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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