[ https://forge.continuent.org/jira/browse/SEQUOIA-1001?page=all ]
Robert Hodges resolved SEQUOIA-1001:
------------------------------------
Assign To: Robert Hodges
Resolution: Fixed
Implemented and checked in.
> Extend Sequoia controller to handle differences in backend driver handling of
> setFetchSize() hints
> --------------------------------------------------------------------------------------------------
>
> Key: SEQUOIA-1001
> URL: https://forge.continuent.org/jira/browse/SEQUOIA-1001
> Project: Sequoia
> Type: New Feature
> Versions: Sequoia 2.10.9
> Environment: All
> Reporter: Robert Hodges
> Assignee: Robert Hodges
> Fix For: sequoia 2.10.10
>
>
> JDBC setFetchSize() calls allow users to request that results be streamed
> back from backends into clients. Sequoia handles setFetchSize calls (for
> example Statement.setFetchSize() consistently, but underlying drivers may
> reject hints, which means that the result set, however large, is just
> streamed into memory. This is a problem because it is necessary to fetch
> subsets of rows for large result sets. Testing with Bristlecone shows that
> even result sets of 100K rows quickly cause the controller to run out of Java
> heap space.
> For example MySQL Connector/J only accepts Integer.MIN_VALUE as a fetch size
> hint and ignores all other settings (i.e., they are the same as 0). Other
> JDBC drivers may have similar behavior. This is a problem because Sequoia
> generally follows the JDBC specification, so we need the ability to map fetch
> size values to what ever wierdness the driver accepts.
> This feature extends the Sequoia ControllerFactory to add a
> DriverComplianceFactory. The factory in turn returns DriverCompliance
> instances, thereby making it possible to extend them. Finally, the
> DriverCompliance class has a new method DriverCompliance.convertFetchSize()
> which converts requested fetch values to a reasonable value for the
> underlying driver. The default implementation simply hands back the
> requested value but other implementations can perform different conversions
> if desired.
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