On Jun28, 2011, at 05:42 , Jeff Davis wrote: > On Mon, 2011-06-27 at 14:50 -0400, Robert Haas wrote: >> Couldn't we also do neither of these things? I mean, presumably >> '[1,10]'::int8range had better work. > > I think that if we combine this idea with Florian's "PAIR" suggestion > here: > http://archives.postgresql.org/message-id/ad4fc75d-db99-48ed-9082-52ee3a4d7...@phlo.org > > then I think we have a solution. > > If we add a type RANGEINPUT that is not a pseudotype, we can use that as > an intermediate type that is returned by range constructors. Then, we > add casts from RANGEINPUT to each range type. That would allow > range(1,2)::int8range > to work without changing the type system around, because range() would > have the signature: > range(ANYELEMENT, ANYELEMENT) -> RANGEINPUT > and then the cast would change it into an int8range. But we only need > the one cast per range type, and we can also support all of the other > kinds of constructors like: > range_cc(ANYELEMENT, ANYELEMENT) -> RANGEINPUT > range_linf_c(ANYELEMENT) -> RANGEINPUT > without additional hassle.
Hm, so RANGEINPUT would actually be what was previously discussed as the "range as a pair of bounds" definition, as opposed to the "range as a set of values" definition. So essentially we'd add a second concept of what a "range" is to work around the range input troubles. I believe if we go that route we should make RANGEINPUT a full-blown type, having "pair of bound" semantics. Adding a lobotomized version just for the sake of range input feels a bit like a kludge to me. Alternatively, we could replace RANGEINPUT simply with ANYARRAY, and add functions ANYRANGE->ANYRANGE which allow specifying the bound operator (<, <= respectively >,>=) after construction. So you'd write (using the functions-as-fields syntax I believe we support) (ARRAY[1,2]::int8range).left_open.right_closed for '(1,2]' and ARRAY[NULL,2]::int8range for '[-inf,2]' All assuming that modifying the type system to support polymorphic type resolution based on the return type is out of the question... ;-) best regards, Florian Pflug -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
