Seonggon Namgung created HIVE-28196:
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Summary: Preserve column stats when applying UDF upper/lower.
Key: HIVE-28196
URL: https://issues.apache.org/jira/browse/HIVE-28196
Project: Hive
Issue Type: Improvement
Reporter: Seonggon Namgung
Assignee: Seonggon Namgung
Current Hive re-estimates column stats (including avgColLen) when it encounters
UDF.
In the case of upper and lower, Hive sets avgColLen to
hive.stats.max.variable.length.
But these UDFs do not change column stats and the default value(100) is too
high for string type key columns, on which upper/lower are usually applied.
This patch keeps input data's avgColLen after applying UDF upper/lower to make
a better query plan.
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