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From "Mamta A. Satoor (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-4115) Provide a way to drop statistics information
Date Tue, 08 May 2012 21:47:49 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4115?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13270864#comment-13270864

Mamta A. Satoor commented on DERBY-4115:

Kristian, thanks for taking the time to review the patch. Here are my answers.
 a) Inconsistent use of tabs and spaces for indentation. 
   I will fix this. Not sure why Eclipse is not consistent in using one vs the others.

 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. 
  I wondered about this myself when I copied the model for update statistics for drop statistics.
My gut feeling is that this was done in order to avoid the conflict with pre-existing 4 parameter
init() method for compress table and hence we may have decided to add a new init method with
5 parameters but I am not 100% sure about this theory. I am planning on uploading a patch
soon which will update upgrade tests and more regular tests for drop statistics. If there
are no comments on that patch, I would like to go ahead and commit that patch. We can address
the redundancy of extra parameter dropStatisticsAll/updateStatisticsAll in a future patch.

 c) Typo in sqlgrammar.jj 
    "By the type" -> "By the time" 
  I will fix this.

 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 
  I will fix this.

 e) What's the reason for the change in Changes10_2? 
  The test after hard upgrades seem to check how many system procedures have public access.
Since the drop statistics procedure has public access(similar to update statistics), we need
to include that in the expected resultset list.

> 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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