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https://issues.apache.org/jira/browse/DRILL-4122?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15183278#comment-15183278
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Sudheesh Katkam commented on DRILL-4122:
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This is actually a bad measure because there are distributions (other than
uniform) with skewness of 0.
> 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
> Assignee: Sudheesh Katkam
>
> 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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