Re: Domains versus polymorphic functions, redux

On Tue, May 24, 2011 at 02:00:54PM -0400, Noah Misch wrote:
> On Tue, May 24, 2011 at 01:28:38PM -0400, Tom Lane wrote:
> > Noah Misch <noah(at)leadboat(dot)com> writes:
> > > On Tue, May 24, 2011 at 12:12:55PM -0400, Tom Lane wrote:
> > >> This is a consequence of the changes I made to fix bug #5717,
> > >> particularly the issues around ANYARRAY matching discussed here:
> > >> http://archives.postgresql.org/pgsql-hackers/2010-10/msg01545.php
> >
> > > We discussed this a few weeks ago:
> > > http://archives.postgresql.org/message-id/20110511093217.GB26552@tornado.gateway.2wire.net
> >
> > > What's to recommend #1 over what I proposed then? Seems like a discard of
> > > functionality for little benefit.
> >
> > I am unwilling to commit to making #2 work, especially not under time
> > constraints; and you apparently aren't either, since you haven't
> > produced the patch you alluded to at the end of that thread.
>
> I took your lack of any response as non-acceptance of the plan I outlined.
> Alas, the wrong conclusion. I'll send a patch this week.

See attached arrdom1v1-polymorphism.patch. This currently adds one syscache
lookup per array_append, array_prepend or array_cat call when the anyarray
type is not a domain. When the type is a domain, it adds a few more. We
could add caching without too much trouble. I suppose someone out there uses
these functions in bulk operations, though I've yet to see it. Is it worth
optimizing this straightway?

For a function like
CREATE FUNCTION f(anyarray, VARIADIC anyarray) RETURNS int LANGUAGE sql
AS 'SELECT array_length($1, 1) + array_length($2, 1)'
we must coerce the variadic argument array to a domain type when the other
anyarray argument(s) compel it. Having implemented that, it was nearly free
to re-support a VARIADIC parameter specifically declared with a domain over an
array. Consequently, I've done that as well.

See here for previously-disclosed rationale:
http://archives.postgresql.org/message-id/20110511191249.GA29592@tornado.gateway.2wire.net

I audited remaining get_element_type() callers. CheckAttributeType() needs to
recurse into domains over array types just like any other array type. Fixed
trivially in arrdom2v1-checkattr.patch; see its test case for an example hole.

nm