Ok, that adds some clarity. Have base types (int32, etc) had the same oid values for a significant number of versions of PgSQL? What I am getting at is this: can I hard code oid values into an access layer for PgSQL? I see that the Java driver uses select statements back into the db to determine the datatype for a given oid. I know for user-defined types that is required, but for base types is it required?
And thanks for the reply! Reggie > -----Original Message----- > From: Tom Lane [mailto:[EMAIL PROTECTED]] > Sent: Sunday, January 05, 2003 12:42 AM > To: Reggie Burnett > Cc: [EMAIL PROTECTED] > Subject: Re: [HACKERS] pgsql oid question > > "Reggie Burnett" <[EMAIL PROTECTED]> writes: > > I have started experimenting with an access layer for pgsql and have a > > question. I had someone on this list tell me that the oid values that > > come back from the server are tag identifiers for that row/column > > combination and are not type indicators. > > I think your someone is confused. There are no identifiers associated > with row/column combinations. > > > Yet, when I create multiple > > tables/columns each having the same type (int32), the same oid keeps > > being returned. > > The OIDs returned in RowDescription messages uniquely identify datatypes > (more specifically, pg_type rows). They will be stable short of DROP > TYPE/CREATE TYPE shenanigans. (However, user-defined types might not > get the same OIDs assigned after a dump/reload cycle. It's probably > reasonable to treat type OIDs as stable for the life of a connection, > but not as constants of nature.) > > OIDs are also used for other purposes, so your confusion may stem from > confusing pg_type OIDs with other OIDs. In the current system > implementation, OIDs are unique row identifiers only within individual > tables --- perhaps not even then, if the table doesn't have a unique > index on its OID field. Thus, a pg_type OID uniquely identifies a > datatype, but that doesn't mean that the same OID number could not > appear in pg_class, pg_rewrite, or other system or user tables. > > regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org
