|| at Nov 10, 2011 at 7:02 pm
The ! prefixing !count has nothing to do with it being "nullable", It's
actually just a regular aggregator that I didn't have a better name for.
Usage of !count looks like this:
(<- [?count] (source !val) (c/!count !val :> ?count))
!count takes in one input variable. Null values are interpreted as "0" and
non-null values are interpreted as "1". !count returns the sum of those
interpreted values. So !count counts the number of non-null values for that
On Thu, Nov 10, 2011 at 10:35 AM, R Daneel wrote:
I'm sure this must be a stupid question: why are !count-parallel and
!count both defined as nullable, whereas other similar (parallel) aggs
(sum, max, min) are not? Is it to prevent count from counting nulls? And
yet one can call (count ...) without the prefix, and one can count ?foo or
!foo, so I'm at a loss to explain the syntax/meaning of the ! prefix on the
count function itself.