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Date: Thu, 23 Sep 2010 16:09:32 -0400 (EDT)
From: "Kristian Waagan (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Updated: (DERBY-4771) Continue investigation of automatic
 creation/update of index statistics
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     [ https://issues.apache.org/jira/browse/DERBY-4771?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Kristian Waagan updated DERBY-4771:
-----------------------------------

    Attachment: derby-4771-2a-prototype_lcc_code_dump.diff

Patch 2a is another code dump, still prototyping.
I am now using an lcc to update the data dictionary directly from the daemon.
The damoen is enabled by default and will write some information to the log. More detailed tracing can be enabled (see the comments in IndexStatisticsDaemon).

If anyone has an application or a db load they can test this with, I'd be happy to know if the daemon works.
To do so, build Derby with the patch, run your app and then grep your derby.log file afterwards for "istat".
It might also crash...
You should see statistics being generated for indexes which don't have them, and potentially also updates of existing stats (depends on many factors, I'll explain more later, but some keywords: row count estimate, table growth, statement compilation).

I'll be away for a week, and will answer any comments when I'm back.
My next step will be to validate/rewrite the logic I added to the table descriptor and the other "catalog classes", potentially followed by some initial tuning of various thresholds, and writing more tests.

> Continue investigation of automatic creation/update of index statistics
> -----------------------------------------------------------------------
>
>                 Key: DERBY-4771
>                 URL: https://issues.apache.org/jira/browse/DERBY-4771
>             Project: Derby
>          Issue Type: Task
>            Reporter: Kristian Waagan
>            Assignee: Kristian Waagan
>         Attachments: derby-4771-1a-prototype_code_dump.diff, derby-4771-1a-prototype_code_dump.stat, derby-4771-1b-prototype_code_dump.diff, derby-4771-2a-prototype_lcc_code_dump.diff, derby.log, error-stacktrace.out, rjall.out, rjall.out
>
>
> Work was started to improve Derby's handling of index statistics. This issue tracks further discussion and work for this task.

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