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https://issues.apache.org/jira/browse/DERBY-4121?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mike Matrigali updated DERBY-4121:
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cardinality statistics only track's the average number of duplicate values per
value in an index. So it is unnecessary to update this if that value is not
changing. Derby uses the indexes directly to
track the distribution of values in given ranges and update statistics has no
affect on this.
So it is not necessary to update as the number of rows grows.
The system has a zero admin way to track the number of rows in the system.
This method is an
estimate and a proposed change to update statistics will improve this
estimate, but don't want users to think that they have to update statistics to
get valid row counts.
> Documentation: more UPDATE_STATISTICS fixes needed for Reference Manual and
> Tuning Derby
> ----------------------------------------------------------------------------------------
>
> Key: DERBY-4121
> URL: https://issues.apache.org/jira/browse/DERBY-4121
> Project: Derby
> Issue Type: Bug
> Components: Documentation
> Affects Versions: 10.5.0.0
> Reporter: Kim Haase
> Priority: Minor
>
> Kathey Marsden comments on DERBY-3787:
> Not a show stopper for the release, but in beginning my buddy testing,
> I noticed the examples should use CALL e.g.
> CALL SYSCS_UTIL.SYSCS_UPDATE_STATISTICS('SAMP','EMPLOYEE','PAY_DESC');
> CALL SYSCS_UTIL.SYSCS_UPDATE_STATISTICS('SAMP', 'EMPLOYEE', null);
> Also in the Tuning Guide under Working with Cardinality Statistics -> When
> Cardinality Statistics Go Stale we should refer users to the
> SYSCS_UTIL.SYSCS_UPDATE_STATISTICS stored procedure to update their
> statistics and cross reference the reference guide.
> Myrna van Lunteren suggests a new issue for this, so I'm filing it.
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