[jira] [Resolved] (TRAFODION-2017) Tune HBase row cache sizes so UPDATE STATS completes

["David Wayne Birdsall (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/TRAFODION-2017?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

David Wayne Birdsall resolved TRAFODION-2017.
---------------------------------------------
    Resolution: Fixed

> 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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