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