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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-2487) Enhance Derby with EXPLAIN Functionality
Date Sun, 22 Feb 2009 18:49:02 GMT

    [ https://issues.apache.org/jira/browse/DERBY-2487?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12675691#action_12675691
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Knut Anders Hatlen commented on DERBY-2487:
-------------------------------------------

Hi Bryan,

I haven't looked at the patch yet, but I've had a brief look at the documentation that you
posted on DERBY-4065 (great work, by the way!), and I noticed that the STMT_TEXT column in
SYSXPLAIN_STATEMENTS was of type LONG VARCHAR (length 32700). Given that the maximum length
of VARCHAR is just 28 characters shorter than LONG VARCHAR, do you think it would be a good
idea to change the data type of that column to VARCHAR? That would allow comparisons on that
column without a cast. Otherwise, I think a statement like "select * from sys.sysxplain_statements
where stmt_text='select * from t'" would result in ERROR 42818: Comparisons between 'LONG
VARCHAR (UCS_BASIC)' and 'CHAR (UCS_BASIC)' are not supported.

> Enhance Derby with EXPLAIN Functionality
> ----------------------------------------
>
>                 Key: DERBY-2487
>                 URL: https://issues.apache.org/jira/browse/DERBY-2487
>             Project: Derby
>          Issue Type: New Feature
>          Components: SQL
>    Affects Versions: 10.2.2.0
>            Reporter: Felix Beyer
>            Assignee: Bryan Pendleton
>            Priority: Minor
>         Attachments: Derby physical XPLAIN schema.png, incorporateTrunkChanges.diff,
RSProtocolNew.pdf, rts.xls, small logical xplain schema.pdf, startRegressionTest.diff, updateRegressionTests.diff,
updateRegressionTests.diff, usage.txt, xplain_patch_v1.txt, xplainClasses.pdf
>
>
> This enhancement extends Derby with EXPLAIN functions. Users want to have more feedback
than they`re getting with the current RuntimeStatistics facility. This extension is based
on the RuntimeStatistics/ResultSetStatistics functions / classes. 

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