Andrew Gierth <andrew@tao11.riddles.org.uk> writes:
> Type-dependent selection of operators has already been done as part of
> parse analysis, no? And the domain -> base conversion is purely a
> relabelling, no? So what semantic change is possible as a result?
Domain conversions are *not* simply relabellings. It's possible now to
have domain-specific functions/operators, and the likely future
evolution of the system is to make that work better rather than remove it.
It's possible that there are specific cases where the UNION optimization
checks could allow domains to be treated as their base types, but
blindly smashing both sides of the check to base is going to break more
cases than it fixes.
regards, tom lane