[ https://issues.apache.org/jira/browse/DERBY-3934?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Kristian Waagan closed DERBY-3934.
----------------------------------

    Resolution: Fixed

Closing this issue.
Some performance results (embedded only) can be seen here: http://www.nabble.com/CLOB-performance-td21831259.html#a21831259
The most relevant result is testFetchLargeClobPieceByPieceModified, followed by testFetchLargeClobOneByOneCharModified and testFetchLargeClobsModified.

There's a small performance hit for the testFetchLargeClobsModified, this may be because we create update sensitive streams unconditionally and that UTF8Reader has been equipped with more functionality. However, the changes to UTF8Reader are required to obtain acceptable performance with the client driver, which always fetches CLOBs piece by piece (through a callable statement using Clob.getSubString).

> Improve performance of reading modified Clobs
> ---------------------------------------------
>
>                 Key: DERBY-3934
>                 URL: https://issues.apache.org/jira/browse/DERBY-3934
>             Project: Derby
>          Issue Type: Improvement
>          Components: JDBC
>    Affects Versions: 10.5.0.0
>            Reporter: Kristian Waagan
>            Assignee: Kristian Waagan
>             Fix For: 10.5.0.0
>
>         Attachments: derby-3934-1a-clob_replace_test.diff, derby-3934-2a-intclob_new_methods.diff, derby-3934-3a-clobupdreader_utf8reader.diff, derby-3934-3a-clobupdreader_utf8reader.stat, derby-3934-4a-getinternalreader_cachedlength.diff, derby-3934-5a-UTF8Reader_cleanup.diff, derby-3934-6a-UTF8Reader_remove_method.diff
>
>
> The performance of reading modified Clobs is poor, which is demonstrated by running a test program selecting a 10 MB Clob and then getting the contents using getSubString:
>  - unmodified Clob (StoreStreamClob) : ~1 300 ms
>  - modified Clob (TemporaryClob): ~156 000 ms
> In this case, the Clob was modified by changing the first character.
> A number of subtasks will be created to handle the various issues, which will be related to both performance and code cleanup.
> For a brief overview, see http://www.nabble.com/Suggestion-for-improving-ClobUpdatableReader-and-related-code-to20308303.html

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