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From "Aman Sinha (JIRA)" <j...@apache.org>
Subject [jira] [Created] (DRILL-4122) Create unit test suite for checking quality of hashing for hash based operators
Date Mon, 23 Nov 2015 18:43:11 GMT
Aman Sinha created DRILL-4122:
---------------------------------

             Summary: Create unit test suite for checking quality of hashing for hash based
operators
                 Key: DRILL-4122
                 URL: https://issues.apache.org/jira/browse/DRILL-4122
             Project: Apache Drill
          Issue Type: Bug
          Components: Functions - Drill
    Affects Versions: 1.3.0
            Reporter: Aman Sinha


We have encountered substantial skew in the hash based operators (hash distribution, hash
aggregation, hash join) for certain data sets.  Two such issues are DRILL-2803, DRILL-4119.
  

It would be very useful to have a unit test suite to test the quality of hashing.  
The number of combinations is large: num_data_types x nullability x num_hash_function_types
(32bit, 64bit, AsDouble variations). Plus, the nature of the data itself.   We would have
to be judicious about picking a reasonable subset of this space.   We should also look at
open source test suites in this area. 



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