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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-2912) Reduce checkpoint cost in truncateEnd phase of SYSCS_INPLACE_COMPRESS_TABLE
Date Mon, 29 Jun 2009 14:07:47 GMT

     [ https://issues.apache.org/jira/browse/DERBY-2912?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Dag H. Wanvik updated DERBY-2912:

    Derby Categories: [Performance]

> Reduce checkpoint cost in truncateEnd phase of SYSCS_INPLACE_COMPRESS_TABLE
> ---------------------------------------------------------------------------
>                 Key: DERBY-2912
>                 URL: https://issues.apache.org/jira/browse/DERBY-2912
>             Project: Derby
>          Issue Type: Improvement
>          Components: Store
>            Reporter: Daniel John Debrunner
>            Priority: Minor
> The truncate phase of SYSCS_INPLACE_COMPRESS_TABLE always performs a checkpoint per container.
For any table this is likely to mean a number of checkpoints (one per index and one for the
base table).
> Potential improvements are:
>    1) Only perform the checkpoint (and the clean of the allocation cache) if the truncate
will actually free some space up.
>    2) Perform the checkpoint once for a table, not once per container.
>    3) Don;t perform a complete checkpoint, just flush the pages for the table/container
being truncated.
> 1) Seems fairly possible, I have no idea if the others are.
> This affects the JUnit tests which perform a inplace compress on SYSDEPENDS, even with
no space to free up the inplace compress takes about 0.5 seconds and upto two seconds with
changes (even on a fairly small table).

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