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From "Kristian Waagan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-4115) Provide a way to drop statistics information
Date Mon, 07 May 2012 11:37:48 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4115?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13269538#comment-13269538

Kristian Waagan commented on DERBY-4115:

Hi Mamta,

I had a look at patch 5. The tests ran sucessfully, and my simple manual invokations behaved
like they should.
Here are some comments, suggestions, and questions about the patch:
 a) Inconsistent use of tabs and spaces for indentation.
 b) Would it be okay to use (indexNameForStatistics == null) instead of
    dropStatisticsAll to reduce the state of the class? The relationship
    could be documented with dropStatistics.
 c) Typo in sqlgrammar.jj
    "By the type" -> "By the time"
 d) SystemProcedures.SYSCS_DROP_STATISTICS:
    o typo in @param indexname. Also, I don't understand the comment about
      indexname being the empty string. Is that allowed? The parser falls over
      if I try to specify it as an argument to the SQL call.
    o incorrect @exception (or @throws) in Javadoc
    o debug println
 e) What's the reason for the change in Changes10_2?

> Provide a way to drop statistics information
> --------------------------------------------
>                 Key: DERBY-4115
>                 URL: https://issues.apache.org/jira/browse/DERBY-4115
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions:
>            Reporter: Kathey Marsden
>            Assignee: Mamta A. Satoor
>         Attachments: DERBY4115_patch1_diff.txt, DERBY4115_patch2_diff.txt, DERBY4115_patch3_diff.txt,
DERBY4115_patch4_diff.txt, DERBY4115_patch5_diff.txt
> Now that DERBY-269 has been resolved,  users can update statistics, but once they do,
they are committed to using and maintaining the statistics, even if it doesn't improve performance
or they have difficulty maintaining the statistics on a regular basis.  It would be good to
have a way to drop statistics information so that users could revert to the prior behavior
if needed.

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