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https://issues.apache.org/jira/browse/DERBY-6283?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13707946#comment-13707946
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Mamta A. Satoor commented on DERBY-6283:
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Mike, I reviewed the patch and here is my understanding of the patch
1)We will pick up single-column unique indexes stats(this is the existing
behavior and not touched by this jira) for disposing
a)if we are dealing with a 10.9 or higher version db and
b)if Property.STORAGE_AUTO_INDEX_STATS_DEBUG_KEEP_DISPOSABLE_STATS is set to
FALSE or not set at all
2)we will dispose off all the stats which are not attached to any indexes for
the given conglomerate(this is the new behavior with this jira) irrespective of
what happens with single-column unique index stats
Just two little nit-picks on the patch and an existing comment
1)Did you mean to write more in the comment below? It looks unfinished
// This loop looks for statistic entries to delete. It deletes
// those entries that don't have a matching conglomerate in the
2)Also, does this existing comment still make sense? The above loop will
include single column unique index if we are dealing with 10.9 and higher db
and if we are not being asked to keep the stats for single column unique index
through Property.STORAGE_AUTO_INDEX_STATS_DEBUG_KEEP_DISPOSABLE_STATS flag.
// Note that the algorithm would drop valid statistics entries if
// working on a subset of the table conglomerates/indexes.
// The above loop has populated "cds" with only existing indexes that
// are not single column unique.
> indexStat daemon processing tables over and over even when there are no
> changes in the tables in soft upgraded database.
> ------------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-6283
> URL: https://issues.apache.org/jira/browse/DERBY-6283
> Project: Derby
> Issue Type: Bug
> Components: Store
> Affects Versions: 10.8.3.1, 10.9.2.2, 10.10.1.3, 10.11.0.0
> Reporter: Mike Matrigali
> Assignee: Mike Matrigali
> Priority: Blocker
> Labels: derby_triage10_11
> Attachments: derby-6283.diff
>
>
> The fix for DERBY-5680 currently requires hard upgrade. A soft upgrade
> database with an orphaned stat row, that can be caused by something like
> DERBY-5681, will cause DERBY to spin eating up 100% of a cpu and possibly all
> the disk bandwith of the disk where the database is located.
> We should implement a fix that can be applied to soft upgraded databases if
> at all possible.
> In soft upgraded databases we can no use the work around of dropping the
> statistics as it is not available
> to soft upgraded db's with version < 10.9. The only current workaround is to
> disable background stats
> completely. Dropping and recreating the suspect table may also work.
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