Re: ORDER/GROUP BY expression not found in targetlist

Tom Lane writes:

> Andreas Seltenreich <seltenreich@gmx.de> writes:
>> Peter Geoghegan writes:
>>> It's surprising that SQL Smith didn't catch something with such simple
>>> steps to reproduce.
>
>> I removed distinct relatively early because it causes a large part of
>> queries to fail due to it not finding an equality operator it likes.  It
>> seems to be more picky about the equality operator than, say, joins.
>> I'm sure it has a good reason to do so?
>
> It's looking for an operator that is known to be semantically equality,
> by virtue of being the equality member of a btree or hash opclass.
> Type path has no such opclass unfortunately.

As do lots of data types in the regression db while still having an
operator providing semantic equivalence.  I was hoping for someone to
question that status quo.  Naively I'd say an equivalence flag is
missing in the catalog that is independent of opclasses.

regards
Andreas