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https://issues.apache.org/jira/browse/SPARK-25146?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16584015#comment-16584015
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Daniel Darabos commented on SPARK-25146:
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Wonderful, thanks! Sorry I missed the fix.
> avg() returns null on some decimals
> -----------------------------------
>
> Key: SPARK-25146
> URL: https://issues.apache.org/jira/browse/SPARK-25146
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.3.0, 2.3.1
> Reporter: Daniel Darabos
> Priority: Major
>
> We compute some 0-10 numbers in a pipeline using Spark SQL. Then we average
> them. The average in some cases comes out to {{null}} to our surprise (and
> disappointment).
> After a bit of digging it looks like these numbers have ended up with the
> {{decimal(37,30)}} type. I've got a Spark Shell (2.3.0 and 2.3.1) repro with
> this type:
> {code}
> scala> (1 to 10000).map(_*0.001).toDF.createOrReplaceTempView("x")
> scala> spark.sql("select cast(value as decimal(37, 30)) as v from
> x").createOrReplaceTempView("x")
> scala> spark.sql("select avg(v) from x").show
> +------+
> |avg(v)|
> +------+
> | null|
> +------+
> {code}
> For up to 4471 numbers it is able to calculate the average. For 4472 or more
> numbers it's {{null}}.
> Now I'll just change these numbers to {{double}}. But we got the types
> entirely automatically. We never asked for {{decimal}}. If this is the
> default type, it's important to support averaging a handful of them. (Sorry
> for the bitterness. I like {{double}} more. :))
> Curiously, {{sum()}} works. And {{count()}} too. So it's quite the surprise
> that {{avg()}} fails.
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