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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-4939) Enable istat daemon and tests
Date Thu, 24 Mar 2011 15:22:05 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4939?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13010703#comment-13010703

Dag H. Wanvik commented on DERBY-4939:

Small comment on the release notes:

> "During query compilation, Derby now checks if the index cardinality statistics for the
tables involved in the query are out of date. If > the statistics are outdated, the query
compiler will schedule a job that updates them in a separate thread. "

Strictly speaking, "out-of-date" is an elusive goal, we can't really claim more than a best
shot using heuristics. So maybe we should
qualify this statement to say something like "deemed out of date", and add a sentence to say
that one can always force an update using SYSCS_UTIL.SYSCS_UPDATE_STATISTICS if the automation
doesn't work well enough for an application?

> Enable istat daemon and tests
> -----------------------------
>                 Key: DERBY-4939
>                 URL: https://issues.apache.org/jira/browse/DERBY-4939
>             Project: Derby
>          Issue Type: Sub-task
>          Components: SQL
>    Affects Versions:
>            Reporter: Kristian Waagan
>            Assignee: Kristian Waagan
>             Fix For:
>         Attachments: derby-4939-1a-enable_istat.diff, releaseNote.html, releaseNote.html,
releaseNote.html, releaseNote.html
> Enable automatic updates and creations of index cardinality statistics, and wire the
tests into the regression suite.

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