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https://issues.apache.org/jira/browse/TRAFODION-2673?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16067312#comment-16067312
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ASF GitHub Bot commented on TRAFODION-2673:
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GitHub user DaveBirdsall opened a pull request:
https://github.com/apache/incubator-trafodion/pull/1154
[TRAFODION-2673] Improve incremental update stats performance
This change improves the performance of incremental UPDATE STATISTICS by
using "WITH NO ROLLBACK" when deleting rows from the persistent sample table.
A CQD, USTAT_DELETE_NO_ROLLBACK, has been added. When set to 'ON' (the
default), we use DELETE WITH NO ROLLBACK on the persistent sample table. When
set to 'OFF', we do the old behavior, that is, a vanilla transactional DELETE.
This CQD is here mostly in order to test and verify the performance
improvement. It can be removed later.
While I was at it, I noticed another CQD that is no longer used anywhere
and removed it.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/DaveBirdsall/incubator-trafodion Trafodion2673
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/incubator-trafodion/pull/1154.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #1154
----
commit e86f4e8e4f72a0d43015713b1dd2dbe8e7a1e7a0
Author: Dave Birdsall <[email protected]>
Date: 2017-06-28T21:53:09Z
[TRAFODION-2673] Improve incremental update stats performance
----
> Improve performance of incremental UPDATE STATISTICS
> ----------------------------------------------------
>
> Key: TRAFODION-2673
> URL: https://issues.apache.org/jira/browse/TRAFODION-2673
> Project: Apache Trafodion
> Issue Type: Improvement
> Components: sql-cmp
> Affects Versions: 2.2-incubating
> Environment: All, but most noticeable on large sample tables
> Reporter: David Wayne Birdsall
> Assignee: David Wayne Birdsall
>
> When running an incremental UPDATE STATISTICS utility, rows satisfying the
> WHERE clause are first deleted from the sample table, then replaced with a
> new sample taken from the base table.
> The statement used to delete rows from the sample table is a vanilla DELETE,
> which performs poorly when the set of rows to be deleted is large. It would
> be better (and much faster) to use DELETE NO ROLLBACK.
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