On Thu, 2010-04-08 at 22:29 -0400, Robert Haas wrote: > 1. knngist wants to use index scans to speed up queries of the form > SELECT ... ORDER BY <column> <op> <constant> (as opposed to the > existing machinery which only knows how to use an index for SELECT ... > ORDER BY <column>). > 2. Window functions want to define windows over a range of values > defined by the underlying data type. To do this, we need to define > what addition and subtraction mean for a particular data type. > 3. Jeff Davis is interested in implementing range types. When the > underlying base type is discrete, e.g. integers, you can say that > [1,3] = [1,4), but only if you know that 3 and 4 are consecutive (in > that order).
To give some context, I started a thread a while ago: http://archives.postgresql.org/pgsql-hackers/2009-10/msg01403.php Tom provided some interesting suggestions in that thread, but I'm not sure they would work for #1 or #2. > It may or may not be worth building the concept of a unit > increment into the type interface machinery, though: one could imagine > two different range types built over the same base type with different > unit increments - e.g. one timestamp range with unit increment = 1s, > and one with unit increment = 1m. Under the first type [4pm,5pm) = > [4pm,4:59:59pm], while under the second [4pm,5pm) = [4pm,4:59pm]. Right. Part of the interface could be a unit() function, and that can return whatever you want. I was originally thinking about it in terms of next() and prev(), but you could build those from +, -, and unit(). Regards, Jeff Davis -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
