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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4940) Tune istat operational characteristics
Date Wed, 16 Feb 2011 18:27:24 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4940?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12995441#comment-12995441

Rick Hillegas commented on DERBY-4940:

There is a discussion about reasonable defaults for the undocumented istat knobs and about
whether additional knobs are needed: http://old.nabble.com/forum/Search.jtp?forum=105&local=y&query=question+about+istats+thresholds

This issue is a place to continue those discussions and, if necessary, to hang patches. At
the moment, we are still planning to not document these knobs. Instead, we would like to gain
experience about how istat behaves in the wild. From that experience, we hope to figure out
whether these are the right knobs, how to set reasonable defaults for them, and whether we
should document how to override Derby's defaults. 

> Tune istat operational characteristics
> --------------------------------------
>                 Key: DERBY-4940
>                 URL: https://issues.apache.org/jira/browse/DERBY-4940
>             Project: Derby
>          Issue Type: Sub-task
>          Components: SQL
>    Affects Versions:
>            Reporter: Kristian Waagan
> The istat feature relies in a few tuning parameters to work properly.
> The main goals of the feature is to avoid stale statistics degrading query performance,
and at the same time not interfere too much with user activity. Some study of applications
"in the field" is necessary to properly size the set of parameters.
> It is also clear that it is impossible to make the feature behave exactly as wanted for
all types of applications. Users that want full control of their statistics, can disable the
istat daemon and manually monitor and update the statistics.

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