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ASF GitHub Bot commented on TRAFODION-2017: ------------------------------------------- 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 ---- 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 ---- > 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. -- This message was sent by Atlassian JIRA (v6.3.4#6332)