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https://issues.apache.org/jira/browse/TRAFODION-2017?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15303043#comment-15303043
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ASF GitHub Bot commented on TRAFODION-2017:
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GitHub user DaveBirdsall opened a pull request:
https://github.com/apache/incubator-trafodion/pull/505
[TRAFODION-2017] Use a maximum HBase row cache of 50 for USTAT sample…
… scans
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/DaveBirdsall/incubator-trafodion Trafodion2017
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/incubator-trafodion/pull/505.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 #505
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commit d03526a2a508097dc8f23ac6fd63abb756a2a98e
Author: Dave Birdsall <dbirds...@apache.org>
Date: 2016-05-26T22:03:10Z
[TRAFODION-2017] Use a maximum HBase row cache of 50 for USTAT sample scans
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> Tune HBase row cache sizes so UPDATE STATS completes
> ----------------------------------------------------
>
> Key: TRAFODION-2017
> URL: https://issues.apache.org/jira/browse/TRAFODION-2017
> Project: Apache Trafodion
> Issue Type: Bug
> Components: sql-cmp
> Affects Versions: 2.0-incubating
> Environment: All, though prevalent on clusters with larger tables
> and/or heavier loads
> Reporter: David Wayne Birdsall
> Assignee: David Wayne Birdsall
> Fix For: 2.1-incubating
>
>
> UPDATE STATISTICS often fails with HBase socket timeout exception and/or
> scanner timeout exception when run with sampling on larger tables or clusters
> with heavy concurrent workloads.
> We have experimented in the past with setting various CQDs on large tables to
> reduce these failures, however we were loathe to set them all the time due to
> fears that this would lengthen elapsed time in non-failure scenarios.
> Some recent work by Carol Pearson however shows that the increase in elapsed
> time is negligible for smaller tables and in failure scenarios the failure
> does not occur quickly, so paying a small penalty in elapsed time to increase
> the probability of success seems a better trade-off.
> Carol's work involves tables of less than 1 billion rows. The existing CQD
> logic is still required for larger tables. But for tables of less than 1
> billion rows, she recommends setting HBASE_ROWS_CACHED_MIN and
> HBASE_ROWS_CACHED_MAX to '50'. This JIRA is written to cover this change.
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