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Date: Fri, 31 Oct 2008 07:19:44 -0700 (PDT)
From: "Kristian Waagan (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Updated: (DERBY-3825) StoreStreamClob.getReader(charPos)
 performs poorly
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     [ https://issues.apache.org/jira/browse/DERBY-3825?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Kristian Waagan updated DERBY-3825:
-----------------------------------

    Attachment: derby-3825-3a-simplification.diff

'derby-3825-3a-simplification.diff' makes the repositioning logic easier to read.
Thanks for the suggestion Knut Anders.

Running tests, will commit and backport to 10.4 when the tests have finished.

> StoreStreamClob.getReader(charPos) performs poorly
> --------------------------------------------------
>
>                 Key: DERBY-3825
>                 URL: https://issues.apache.org/jira/browse/DERBY-3825
>             Project: Derby
>          Issue Type: Bug
>          Components: JDBC, Store
>    Affects Versions: 10.5.0.0
>            Reporter: Kristian Waagan
>            Assignee: Kristian Waagan
>             Fix For: 10.5.0.0
>
>         Attachments: derby-3825-0a-preview.diff, derby-3825-1a-reset_readpositioninbuffer.diff, derby-3825-2a-internalReader_repositioning.diff, derby-3825-2a-internalReader_repositioning.stat, derby-3825-2b-internalReader_repositioning.diff, derby-3825-3a-simplification.diff
>
>
> StoreStreamClob.getReader(charPos) performs poorly because it resets the underlying stream and skips data until it reached the requested character position. Not only does the data has to be skipped, it also has to be decoded (UTF-8).
> The problem is exposed through EmbedClob.getSubString, which causes extremely bad performance for the client driver because the locator based Clob implementation uses this method.
> For the record, there is another read buffer size issue that exaggerates the problem (it will probably be handled under DERBY-3769, and also DERBY-3818).

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