[jira] [Created] (DRILL-4122) Create unit test suite for checking quality of hashing for hash based operators

["Aman Sinha (JIRA)" <ji...@apache.org>]

Aman Sinha created DRILL-4122:
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             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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