Try it! Also ... Oracle may be smart enough to not count all rows if you're comparing with 0, but Postgres is not. In a Postgres form of this query we really want to use "exists". I've not bothered when porting the APM because it's not used all that often and the number of packages and versions will grow over time perhaps to the hundreds, but not to the tens of thousands.
But for any check on a sizable table, "exists" is the way to go in Postgres. It's considerably faster in the "true" case, for all practical cases the same in the "false" case as counting.
