> I know a count of the whole table takes about a minute tho. But the filter > group by was ~1s as the grouping was done on about < 50 rows of the filtered result.

Yeah, that makes sense.

I'm running some queries in production that take a 150 million row table, filter it down to ~100-300k rows which are then aggregated/grouped. This usually takes < 1s. However, if I'd try to do a count(*) on the table, that'd be around a minute as well.

> Without knowing the original query above was using it's speculation on why it was slow and mine was fast. My argument is just that SQL Server isn't magically slow. MySQL/PostgreSQL/SQL Server are super fast. And if you don't massage the database it can be super slow too.

Yeah. The query / query plan will be needed to go more in-depth on these kind of discussions. The amount of disk vs memory hits during execution obviously as well.

Anyway, I just wanted to understand if SQL Server was e.g. an order of magnitude faster than Postgres when scanning a large number of tuples. But I guess the answer to that is: probably not.