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From "Mamta A. Satoor (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3788) Provide a zero-admin way of updating the statisitcs of an index
Date Tue, 10 Mar 2009 14:38:51 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3788?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12680478#action_12680478
] 

Mamta A. Satoor commented on DERBY-3788:
----------------------------------------

Bryan, thanks for taking the time for this jira entry. Yes, I was planning on using nowait
so that we do not wait and eventually possibly locking issues with parent. This is exactly
what we do in InsertResultSet.getSetAutoincrementValue as shown below
try 
{
	/* If tcToUse == tc, then we are using parent xaction-- this
	   can happen if for some reason we couldn't start a nested
	   transaction
	   */
	newValue = dd.getSetAutoincrementValue(
		   constants.autoincRowLocation[index],
		   tcToUse, true, aiCache[index], (tcToUse == tc));
}
catch (StandardException se)
{
	if (tcToUse == tc)
	{
		/* we've using the parent xaction and we've timed out; just
		   throw an error and exit.
		*/
		throw se;
	}
	if (se.getMessageId().equals(SQLState.LOCK_TIMEOUT))
	{
		// if we couldn't do this with a nested xaction, retry with
		// parent-- we need to wait this time!
		newValue = dd.getSetAutoincrementValue(
			constants.autoincRowLocation[index],
			tc, true, aiCache[index], true);
	}


> Provide a zero-admin way of updating the statisitcs of an index
> ---------------------------------------------------------------
>
>                 Key: DERBY-3788
>                 URL: https://issues.apache.org/jira/browse/DERBY-3788
>             Project: Derby
>          Issue Type: New Feature
>          Components: Performance
>    Affects Versions: 10.5.0.0
>            Reporter: Mamta A. Satoor
>            Assignee: Mamta A. Satoor
>         Attachments: DERBY3788_patch1_diff.txt, DERBY3788_patch1_stat.txt, DERBY3788_patch2_diff.txt,
DERBY3788_patch2_stat.txt, DERBY3788_patch3_diff.txt, DERBY3788_patch3_stat.txt, DERBY3788_update_all_missing_stats_after_bind_patch4_diff.txt,
DERBY3788_update_all_missing_stats_after_bind_patch4_stat.txt, DERBY_3788_Mgr.java, DERBY_3788_Repro.java
>
>
> DERBY-269 provided a manual way of updating the statistics using the new system stored
procedure SYSCS_UTIL.SYSCS_UPDATE_STATISTICS. It will be good for Derby to provide an automatic
way of updating the statistics without requiring to run the stored procedure manually. There
was some discussion on DERBY-269 about providing the 0-admin way. I have copied it here for
reference.
> *********************
> Kathey Marsden - 22/May/05 03:53 PM 
> Some sort of zero admin solution for updating statistics would be prefferable to the
manual 'update statistics' 
> *********************
> *********************
> Mike Matrigali - 11/Jun/08 12:37 PM 
> I have not seen any other suggestions, how about the following zero admin solution? It
is not perfect - suggestions welcome. 
> Along with the statistics storing, save how many rows were in the table when exact statistics
were calculated. This number is 0 if none have been calculated because index creation happened
on an empty table. At query compile time when we look up statistics we automatically recalculate
the statistics at certain threshholds - say something like row count growing past next threshhold
: 10, 100, 1000, 100000 - with upper limit being somewhere around how many rows we can process
in some small amount of time - like 1 second on a modern laptop. If we are worried about response
time, maybe we background queue the stat gathering rather than waiting with maybe some quick
load if no stat has ever been gathered. The background gathering could be optimized to not
interfere with locks by using read uncommitted. 
> I think it would be useful to also have the manual call just to make it easy to support
customers and debug issues in the field. There is proably always some dynamic data distribution
change that in some case won't be picked up by the automatic algorithm. Also just very useful
for those who have complete control of the create ddl, load data, run stats, deliver application
process. 
> *********************

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