I’m having trouble with count distinct reflections
My SQL is simple:
“SELECT count(distinct id) FROM Common.xx where event_time = ‘2022-5-20’”
But this query only accelerated by raw reflection, not the aggregation reflection.
As far as I know, there are two ways to solve this:
- use select ndv(id) instead. But ndv is an approximation of count.
- create a VDS using select count(distinct xx) and create raw reflection on it. But this may result in plenty of redundant VDSs
So, is there any other better solutions for count distinct?