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Posted to dev@hive.apache.org by "Zoltan Haindrich (Jira)" <ji...@apache.org> on 2020/02/14 16:38:00 UTC

[jira] [Created] (HIVE-22893) Enhance data size estimation for fields computed by UDFs

Zoltan Haindrich created HIVE-22893:
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             Summary: Enhance data size estimation for fields computed by UDFs
                 Key: HIVE-22893
                 URL: https://issues.apache.org/jira/browse/HIVE-22893
             Project: Hive
          Issue Type: Improvement
          Components: Statistics
            Reporter: Zoltan Haindrich
            Assignee: Zoltan Haindrich


Right now if we have columnstat on a coumn ; we use that to estimate things about the column; - however if an UDF is executed on a column ; the resulting column is treated as unknown thing and defaults are assumed.

An impovement could be to give wide estimation(s) in case of frequently used udf.

For example; consider {{substr(c,1,1)}} ; no matter what the input; the output is at most a 1 long string



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