This is logically `sum( if(isnull(col), 0, col) )` right? On Tue, Oct 23, 2018 at 2:58 PM 陶 加涛 <taojia...@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 <m...@clearstorydata.com> > *日期**: *2018年10月23日 星期二 12:28 > *收件人**: *"taojia...@gmail.com" <taojia...@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 <taojia...@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 > > > >
