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From Wenchen Fan <cloud0...@gmail.com>
Subject Re: About introduce function sum0 to Spark
Date Tue, 23 Oct 2018 07:23:15 GMT
This is logically `sum( if(isnull(col), 0, col) )` right?

On Tue, Oct 23, 2018 at 2:58 PM 陶 加涛 <taojiatao@gmail.com> wrote:

> The name is from Apache Calcite, And it doesn’t matter, we can introduce
> our own.
>
>
>
>
>
> ---
>
> Regards!
>
> Aron Tao
>
>
>
> *发件人**: *Mark Hamstra <mark@clearstorydata.com>
> *日期**: *2018年10月23日 星期二 12:28
> *收件人**: *"taojiatao@gmail.com" <taojiatao@gmail.com>
> *抄送**: *dev <dev@spark.apache.org>
> *主题**: *Re: About introduce function sum0 to Spark
>
>
>
> That's a horrible name. This is just a fold.
>
>
>
> On Mon, Oct 22, 2018 at 7:39 PM 陶 加涛 <taojiatao@gmail.com> wrote:
>
> Hi, in calcite, has the concept of sum0, here I quote the definition of
> sum0:
>
>
>
> Sum0 is an aggregator which returns the sum of the values which
>
> go into it like Sum. It differs in that when no non null values
>
> are applied zero is returned instead of null..
>
>
>
> One scenario is that we can use sum0 to implement pre-calculation
> count(pre-calculation system like Apache Kylin).
>
>
>
> It is very easy in Spark to implement sum0, if community consider this is
> necessary, I would like to open a JIRA and implement this.
>
>
>
> ---
>
> Regards!
>
> Aron Tao
>
>
>
>

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