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From DaveBirdsall <...@git.apache.org>
Subject [GitHub] incubator-trafodion pull request: [TRAFODION-2017] Use a maximum H...
Date Thu, 26 May 2016 23:19:29 GMT
Github user DaveBirdsall commented on a diff in the pull request:

    https://github.com/apache/incubator-trafodion/pull/505#discussion_r64837288
  
    --- Diff: core/sql/ustat/hs_globals.cpp ---
    @@ -546,10 +557,11 @@ NABoolean HSGlobalsClass::setHBaseCacheSize(double sampleRatio)
       Int64 workableCacheSize = (Int64)(sampleRatio * calibrationFactor);
       if (workableCacheSize < 1)
         workableCacheSize = 1;  // can't go below 1 unfortunately
    +  else if (workableCacheSize > 50)
    +    workableCacheSize = 50; 
     
    -  Int32 max = getDefaultAsLong(HBASE_NUM_CACHE_ROWS_MAX);
    -  if ((workableCacheSize < 10000) && // don't bother if 10000 works
    -      (max == 10000))  // don't do it if user has already set this CQD
    +  Int32 maxDefault = getDefaultAsLong(HBASE_NUM_CACHE_ROWS_MAX);
    +  if (maxDefault == 10000) // don't do it if user has already set this CQD
    --- End diff --
    
    Thanks for the suggestion for NADefaults::getProvenance(). I'll make this change.
    
    In the case that the user sets the CQD him/herself, I wanted to give them complete freedom
to experiment as they please. Higher values may make UPDATE STATS run faster (though experiements
suggest not by much). The trade-off in using higher values is an increased risk of failure.


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