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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-269) Provide some way to update index cardinality statistics (e.g. reimplement update statistics)
Date Tue, 15 Jul 2008 11:53:31 GMT

    [ https://issues.apache.org/jira/browse/DERBY-269?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12613587#action_12613587

Knut Anders Hatlen commented on DERBY-269:

I've only had a brief look at the patch, so I haven't studied the details, but the general
approach looks fine to me. Some questions/comments:

  - since the code is copied from UpdateStatisticsConstantAction, I assume USCA will be removed
from the repository in a later patch?

  - UpdateStatisticsConstantAction uses a strange mix of tabs and spaces for indentation.
It would be great if the indentation is cleaned up when the code is moved.

  - SystemProcedures.SYSCS_UPDATE_STATISTICS() uses tabs/spaces inconsistently

  - comment in upgradeTests/_Suite.java has the wrong version number:
+        {10, 4, 1, 3}, // (April 24, 2008 / SVN 648739)

  - SYSCS_UPDATE_STATISTICS is added to Changes10_2. Shouldn't that file only test procedures
that were added in Derby 10.2?

> Provide some way to update index cardinality statistics (e.g. reimplement update statistics)
> --------------------------------------------------------------------------------------------
>                 Key: DERBY-269
>                 URL: https://issues.apache.org/jira/browse/DERBY-269
>             Project: Derby
>          Issue Type: New Feature
>          Components: SQL
>    Affects Versions:,,,,
>            Reporter: Stan Bradbury
>            Assignee: Mamta A. Satoor
>         Attachments: DERBY269_update_statistics_svndiff_ver1.txt, DERBY269_update_statistics_svnstat_ver1.txt
> Performance problems are being reported that can be resolved by updating the cardinality
statistics used by the optimizer.  Currently the only time the statistics are guaranteed to
be an up-to-date is when the index is first created on a fully populated table.  This is most
easily accomplished on an existing table by using the command: 
>    alter table <table-name> compress [sequential]  
> Compress table is an I/O intensive task.  A better way to achieve this would be to re-enable
parser support for the 'update statistics' command or re-implement the update in some other

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