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From amansinha100 <...@git.apache.org>
Subject [GitHub] drill pull request #517: DRILL-4704 fix
Date Tue, 12 Jul 2016 17:56:41 GMT
Github user amansinha100 commented on a diff in the pull request:

    https://github.com/apache/drill/pull/517#discussion_r70487824
  
    --- Diff: exec/java-exec/src/main/codegen/templates/Decimal/CastIntDecimal.java ---
    @@ -64,7 +64,15 @@ public void setup() {
     
         public void eval() {
             out.scale = (int) scale.value;
    -        out.precision = (int) precision.value;
    --- End diff --
    
    The eval() method is called for every row, so there will be a performance overhead.  I
 agree about the storage cost if we assume worst case precision; however the per-row evaluation
should be as lightweight as possible and likely outweighs the storage consideration.  One
option is to treat the IntDecimal and BigIntDecimal separately.  For IntDecimal the max int
value is 2^31 - 1 which has a max precision of 10.  Similarly, there is an upper bound on
the BigIntDecimal.  You could initialize the precision in the setup() method which is called
*once*  per new schema (in the normal case the schema of that column does not change, this
would avoid unnecessarily computing the precision).  


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