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Posted to issues@trafodion.apache.org by "ASF GitHub Bot (JIRA)" <ji...@apache.org> on 2017/04/03 20:20:41 UTC
[jira] [Commented] (TRAFODION-25) Insert, delete and update
operators should use specialized cost method
[ https://issues.apache.org/jira/browse/TRAFODION-25?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15954101#comment-15954101 ]
ASF GitHub Bot commented on TRAFODION-25:
-----------------------------------------
GitHub user DaveBirdsall opened a pull request:
https://github.com/apache/incubator-trafodion/pull/1043
[TRAFODION-25] Temporary code for UPDATE costing
This adds some temporary code for UPDATE costing.
The existing code returns a constant value for cost on all UPDATE operations; it is a stub that was put in when the predecessor product was ported to Hadoop and HBase. The temporary code is a copy of the costing code for DELETE. It is being put in because we have an immediate need for parallel UPDATE plans in a particular application, which you don't get with the current stub.
This temporary code, of course, uses the DELETE theory of operation, which understates the costs for UPDATE in general. So it is a stop-gap until better code can be written.
To turn on this code, one must issue CQD HBASE_UPDATE_COSTING 'ON'. Without this CQD, the old stub, a constant cost of 1, will be used.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/DaveBirdsall/incubator-trafodion Trafodion25u
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/incubator-trafodion/pull/1043.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 #1043
----
commit 55e65d2b2a65153c6d5ef58d994980795560f72f
Author: Dave Birdsall <db...@apache.org>
Date: 2017-04-03T20:15:46Z
[TRAFODION-25] Temporary code for UPDATE costing
----
> Insert, delete and update operators should use specialized cost method
> -----------------------------------------------------------------------
>
> Key: TRAFODION-25
> URL: https://issues.apache.org/jira/browse/TRAFODION-25
> Project: Apache Trafodion
> Issue Type: Bug
> Components: sql-cmp
> Reporter: Qifan Chen
> Assignee: David Wayne Birdsall
> Labels: performance
>
> In Trafodion, insert, delete and update operators do not use a specialized cost method that model the true operation involved.
> As a result, these operators can be assigned a zero cost and the query plan may not be optimal. In one example, a delete query against a partitioned table may get a serial plan.
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