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https://issues.apache.org/jira/browse/SPARK-5680?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14587473#comment-14587473
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Venkata Ramana G commented on SPARK-5680:
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Holman, You are right that column with all NULL values should return NULL.
As my motivation was to fix udaf_number_format.q, "select sum('a') from src"
returns 0 in hive, mysql.
and "select cast('a' as double) from src" returned NULL in hive.
I assumed or rather wrongly analysed it as "Sum of ALL NULLs return 0" and this
has introduced the problem.
I apologize for this and will submit the patch to revert that fix.
"select sum('a') from src" returning 0 in hive and mysql created this
confusion, is still not clear.
> Sum function on all null values, should return zero
> ---------------------------------------------------
>
> Key: SPARK-5680
> URL: https://issues.apache.org/jira/browse/SPARK-5680
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Reporter: Venkata Ramana G
> Assignee: Venkata Ramana G
> Priority: Minor
> Fix For: 1.3.1, 1.4.0
>
>
> SELECT sum('a'), avg('a'), variance('a'), std('a') FROM src;
> Current output:
> NULL NULL NULL NULL
> Expected output:
> 0.0 NULL NULL NULL
> This fixes hive udaf_number_format.q
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