On Sun, Feb 19, 2006 at 01:26:31AM -0500, Tom Lane wrote:
> elein <elein@varlena.com> writes:
> > I've got a domain based on a text type.
> > I've overridden the equal operator with
> > lower(text) = lower(text).
>
> This won't work, you need to make a type instead.
>
Actually I can do and have done this. It is being tested now.
I did create an opclass. It creates a UNIQUE index just fine
for the type using the lower() functionality. *If* it passes
all of my testing I'll publish it tomorrow on general bits.
Perhaps folks can help try to break it when I publish (or
if you are around today Sunday, you can test in advance--email me
directly.)
If it doesn't pass the tests, well, I'm hoping
it will be functionally close enough for common use. This
implementation is all in SQL and plperl--no C code.
Now my only complaint is that ORDER BY requires the USING op
when it should recognize the information in the opclass for
btree > and < for the type of the sort column. I can explain
why it doesn't recognize the opclass information, but I think
it should.
> > If this is the way domains really are, I would strongly suggest
> > expanding create domain to merge with create type (under) and
> > allow us to list the basic functions.
>
> IMHO, the exact difference between a domain and a type is you get to
> choose your own definitions of the basic operations on a type. There's
> no free lunch: as soon as you start substituting operations the
> complexity involved goes up by an order of magnitude.
Type inheritance for base types should work by inheriting all of the
parent's definitions and overriding them only as necessary. What I'm
trying to do is to demonstrate that we can weasle this functionality
using domains.
--elein
elein@varlena.com
>
> regards, tom lane
>
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