Adrian Klaver <adrian.klaver@aklaver.com> writes:
> On 09/17/2015 06:54 AM, Tom Lane wrote:
>> Well, that's true: the parser actually looks up the operator named "<>"
>> for the given data types, and IS DISTINCT FROM is just a prefilter on
>> that to do the right thing with nulls. So because type point has an
>> operator that's physically named "<>", that case works.
> If you use '<>' explicitly, otherwise:
> test=> select '(1,2)'::point is distinct from '(1,3)'::point;
> ERROR: operator does not exist: point = point
Ah, sorry, actually what IS [NOT] DISTINCT FROM looks up is the "="
operator. The core point remains, though, that this is a name-based
lookup rather than an opclass-based one. I'd like to get us moved
over to using opclass-based lookups for all cases where the system
currently assumes that operators named "=" or "<>" necessarily behave
in a particular way. However, that would leave point and some of the
other weirder datatypes even further out in the cold than they are now.
regards, tom lane
