Tom Lane schrieb am 13.01.2020 um 15:19: > what it is is attaching DISTINCT to a window function itself. > I'd still ask whether it's well-defined though, or even minimally > sensible. Window functions are generally supposed to produce one > row per input row --- how does that square with the implicit row > merging of DISTINCT? They're also typically row-order-sensitive > --- how does that work with DISTINCT? Also, to the extent that > this is sensible, can't you get the same results already today > with appropriate use of window framing options?
I find the example using array_agg() and cumulative window functions a bit confusing as well, but I think there are situations where having this is really helpful, e.g.: count(distinct some_column) over (partition by something) I know it's not an argument, but Oracle supports this and porting queries like that from Oracle to Postgres isn't really fun. Thomas