PG Bug reporting form <noreply@postgresql.org> writes:
> The psql command line for MacOS looks to external DNS resolution first.
> Once it fails, it then looks to the local machines DNS to resolve hostname.
Neither psql nor libpq (or indeed anything in PG) contain their own
DNS resolution code. It's just using whatever behavior the local libc
provides for that.
Apple's libraries do indeed have some nonstandard DNS resolution behavior,
though. Some quick poking around here suggests that "scutil --dns" might
help you investigate how that's configured on your machine.
Also worth noting is that the PG community at large has no idea what AWS
may have done to versions that they provide; if this isn't a purely
stock psql, you should probably be asking AWS about it.
regards, tom lane