Shohei Okumiya created HIVE-28302:
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Summary: Let SUM UDF return NULL when all rows have non-numeric
texts
Key: HIVE-28302
URL: https://issues.apache.org/jira/browse/HIVE-28302
Project: Hive
Issue Type: Improvement
Components: UDF
Affects Versions: 4.0.0
Reporter: Shohei Okumiya
Assignee: Shohei Okumiya
The ANSI standard says UDAF should return NULL when all inputs are NULL.
Hive is very generous and accepts non-numeric texts as input for SUM. To give
some consistency to the generous specification, we believe `SUM(string_col)`
should behave in the same way as `SUM(CAST(string_col AS DOUBLE))`.
However, Hive's SUM returns 0.0 in that case.
{code:java}
> SELECT SUM(CAST(null AS STRING)), SUM('invalid num'), SUM(CAST('invalid num'
> AS DOUBLE));
+-------+------+-------+
| _c0 | _c1 | _c2 |
+-------+------+-------+
| NULL | 0.0 | NULL |
+-------+------+-------+ {code}
We see some more discussions in https://github.com/apache/hive/pull/5091.
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