From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | "David E(dot) Wheeler" <david(at)kineticode(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, pgsql-hackers(at)postgresql(dot)org, lr(at)pcorp(dot)us |
Subject: | Re: Domains versus polymorphic functions, redux |
Date: | 2011-06-03 18:27:19 |
Message-ID: | 2885.1307125639@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> The real crux of the issue here is: under what circumstances should we
> look through the domain wrapper around an underlying type, and under
> what circumstances should we refrain from doing so?
That's half of it. The other half is: when we *do* look through the
wrapper, is that equivalent to having implicitly inserted a downcast
to the base type, so that the results are now indistinguishable from
having given a base-type value to begin with? Or is the expression's
behavior still affected by the fact of having given a domain value,
and if so, how exactly?
I assert that matching a domain-over-array to an ANYARRAY parameter
certainly involves having "looked through the wrapper". It's
considerably fuzzier though what should happen when matching a domain
to ANYELEMENT.
regards, tom lane
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