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https://issues.apache.org/jira/browse/DERBY-6940?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16056079#comment-16056079
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Harshvardhan Gupta commented on DERBY-6940:
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Another thing, I am able to write and read the minVal and maxVal as strings
successfully using their toString methods, but when trying to store the
original DataValueDescriptor object, I get the following error while trying to
read the statistics -
ERROR XSDA8: Exception during restore of a serializable or SQLData object of cla
ss
ERROR XJ001: Java exception: 'java.lang.ClassCastException: java.lang.String can
not be cast to org.apache.derby.iapi.types.DataValueDescriptor: java.io.StreamCo
rruptedException'.
ERROR XJ001: Java exception: 'java.lang.String cannot be cast to org.apache.derb
y.iapi.types.DataValueDescriptor: java.lang.ClassCastException'.
Storing minVal and maxVal using String is not preferred for comparisons later
on, I am trying to store the original object.
> Enhance derby statistics for more accurate selectivity estimates.
> -----------------------------------------------------------------
>
> Key: DERBY-6940
> URL: https://issues.apache.org/jira/browse/DERBY-6940
> Project: Derby
> Issue Type: Sub-task
> Components: SQL
> Reporter: Harshvardhan Gupta
> Assignee: Harshvardhan Gupta
> Priority: Minor
> Attachments: DERBY-6940_2.diff, derby-6940.diff
>
>
> Derby should collect extra statistics during index build time, statistics
> refresh time which will help optimizer make more precise selectivity
> estimates and chose better execution paths.
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