| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Peter Eisentraut <peter_e(at)gmx(dot)net> |
| Cc: | pgsql-hackers(at)postgresql(dot)org, "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> |
| Subject: | Re: Distinct types |
| Date: | 2008-11-01 20:38:06 |
| Message-ID: | 17750.1225571886@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
> On Friday 31 October 2008 17:01:05 Kevin Grittner wrote:
>> (1) Can you compare a literal of the base type?
> No, unless you create additional casts or operators.
>> (2) Can you explicitly cast to the base type?
> There is an implicit AS ASSIGNMENT cast between the base type and the distinct
> type in each direction.
Hmm ... so out-of-the-box, a distinct type would have no applicable
functions/operators whatsoever. You couldn't even create an index on
it. This seems a bit too impoverished to be useful. And given the
known gotchas with creating functions/operators on domains, I'm not
convinced someone could fix the problem by creating specialized
functions for their distinct type. Even if they could fix it,
having to set up a custom btree opclass in order to have an index
seems to take this out of the "easy to use" category.
regards, tom lane
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