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From "Kristian Waagan (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-3934) Improve performance of reading modified Clobs
Date Tue, 25 Nov 2008 18:15:44 GMT

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

Kristian Waagan updated DERBY-3934:
-----------------------------------

    Attachment: derby-3934-2a-intclob_new_methods.diff

'derby-3934-2a-intclob_new_methods.diff' adds two new methods to the InternalClob interface;
getUpdateCount and isReleased.
They can be used to determine if the content of a Clob has been changed, and if the internal
Clob representation has been changed or the Clob has been closed.
The isReleased() method will be used to detect when a read-only Clob representation is changed
to a writable representation due to a user's request to modify the content (i.e. setString).

The code is currently not being used, but it will be by the new implementation of ClobUpdatableReader
(not yet posted - I do have a prototype if anyone is interested).

Patch ready for review.

> 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
>         Attachments: derby-3934-1a-clob_replace_test.diff, derby-3934-2a-intclob_new_methods.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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