On Thu, Jan 06, 2011 at 02:25:01AM +0900, Hitoshi Harada wrote: > 2011/1/5 Jeff Davis <pg...@j-davis.com>: > > On Tue, 2011-01-04 at 23:04 +0900, Hitoshi Harada wrote: > >> > CREATE TYPE numrange > >> > AS RANGE (SUBTYPE=numeric, SUBTYPE_CMP=numeric_cmp); > >> > >> I am interested in how you define increment/decrement operation > >> of range value in discrete types. The window functions and > >> PARTITION also want to represent RANGE but there's no clear > >> solution. > > > > The user would specify a "canonical" function like: > > > > CREATE TYPE int4range AS RANGE (SUBTYPE=int4, SUBTYPE_CMP=btint4cmp, > > CANONICAL=my_int4range_canonical); > > > > That function would be called when constructing ranges on input or after > > a computation, and could change something like (1,4] into [2,4] if you > > prefer the latter form. > > > > So the range types would not have increments, decrements, granules, or > > knowledge about the "difference" type (e.g. "interval" is the difference > > type for timestamp). > > To canonicalize, it might be ok. I wonder if you won't operate on > the range types like extending their bounds or iterate/enum values > from start to end. In such situation, I bet you'll need to know how > to walk values step by step. > > > What support do you need/want from range types to help with new window > > function features? > > > My argument is here: > http://archives.postgresql.org/message-id/aanlktimfmqmbzj5ctxve_pwt_zmcuhpoet3gaqq6p...@mail.gmail.com > > For any type to calculate boundary based on RANGE clause in window > functions, we need some type interface mechanism in the core to know > how to add / subtract values to reach the boundary from the current > value. For example, > > SELECT count(*) OVER (ORDER BY n_int RANGE BETWEEN 10 PRECEDING AND 5 > FOLLOWING) FROM tbl;
I'm not sure I get the connection between this type of range and the "range types" Jeff is working on. Jeff's work involves a way to create types which represent ranges over types which have some kind of ordering, although not necessarily a successor operation. Had you planned to cast to an integer range in the process of doing this window? Cheers, David. -- David Fetter <da...@fetter.org> http://fetter.org/ Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter Skype: davidfetter XMPP: david.fet...@gmail.com iCal: webcal://www.tripit.com/feed/ical/people/david74/tripit.ics Remember to vote! Consider donating to Postgres: http://www.postgresql.org/about/donate -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
