Re: Operator class group proposal

Martijn van Oosterhout  writes:
> On Wed, Dec 13, 2006 at 04:27:09PM -0500, Tom Lane wrote:
>> we should invent the notion of "operator class groups", which identify
>> sets of compatible operator classes.

> I think it's a good idea, though I would point out that in the examples
> given it's the underlying types that are compatable, not the classes.

Well, I didn't try very hard to provide a complete set of examples,
but here is one addressing that point: the string types have one set of
opclasses involving < = > and one set involving ~<~ ~=~ ~>~ (the
"pattern_ops" opclasses).  These would need to be distinct class groups
since in fact they have incompatible semantics.  Reverse-sort opclasses
would be another example.

> Other names I can think of:
> - type class
> - type group
> - compatability class
> - operator class set
> None of which sound any good :(

Yeah, I'm drawing a blank on good names too.  In the absence of any
better idea I'm inclined to re-use some word that's already a keyword,
rather than invent a new one.  (GROUP is already a fully reserved word,
I think because it's used in GROUP BY, so it wouldn't pose any parsing
problems.)
		regards, tom lane