On 07-02-2015 AM 12:10, Tom Lane wrote: > Amit Langote <langote_amit...@lab.ntt.co.jp> writes: >> I wonder why I cannot find a way to get a range type for a given (sub-) >> type. I would like to build a RangeType from Datum's of lower and upper >> bounds. Much like how construct_array() builds an ArrayType from a Datum >> array of elements given elements' type info. > >> Is there some way I do not seem to know? If not, would it be worthwhile >> to make something like construct_range() that returns a RangeType given >> Datum's of lower and upper bounds and subtype info? > > There is no good reason to assume that a range type exists at all, much > less that it is unique for a subtype. (Read the CREATE TYPE documentation > if you're unclear as to why not.) You have not said what you're trying to > accomplish, but this seems like a dead end. >
We do have a number of built-in range types which we can safely assume to exist with whatever default behavior they are hard-coded with (which I guess are not 'ALTER TYPE'-able). Those existing range types cover a useful set of sub-types which are probably also the potential candidates to be used for range partitioning. Now, one may define a new range type for a given sub-type with a different subopclass, subcollation, subcanonical or subdiff, which is perhaps the problem you are mentioning. Perhaps not very appropriate a solution, but how about a rngtypisdefault (for a sub-type) flag? Sorry I didn't mention before about an idea I am trying to implement with this - it is to serialize range partition bounds as a range type value per partition key column. The serialized representation of a range partition bound for a partition then effectively becomes an anyarray of anyrange: + rangebounds = construct_array(datum, + partnatts, + ANYRANGEOID, + -1, + false, + 'd'); each element of the passed datum array is a range type value of the corresponding subtype. Now, range types may not yet be ripe for internal use but the above idea kind of works modulo the absence of infrastructure I was asking for in OP. Am I still missing something? Thanks, Amit -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
