distinctapprox
distinctapprox(T.‘a) 🡒 number, aggregator
The aggregator computes an approximation of how many distinct elements there are. Two elements a and b are considered identical if a == b. It is provided as an alternative to distinct, but with better performance. As a rule of thumb, this aggregator is intended for vectors beyond 1 million elements.
table T = with
[| as A, as B |]
[| 0, "a" |]
[| 0, "a" |]
[| 0, "b" |]
[| 1, "b" |]
[| 1, "c" |]
table G[gdim] = by T.B
where T.B != "c"
show table "" a1b4 with
gdim
distinctapprox(T.A)
group by gdim
The aggregator distinctapprox supports text and number data types. It returns 0 on empty groups.
Advanced remark: The approximation is based on HyperLogLog.