On Thu, Jun 08, 2006 at 12:19:49PM -0400, Greg Stark wrote: > > "Jim C. Nasby" <[EMAIL PROTECTED]> writes: > > > On Thu, Jun 08, 2006 at 11:42:49AM -0400, Greg Stark wrote: > > > But I seem to recall some headaches with that approach. > > > > What happens if you > > > > ALTER TABLE ... ADD new_column int DEFAULT 1; > > ALTER TABLE ... ALTER new_column SET DEFAULT 2; > > Ah yes. Keeping track of multiple old defaults and when they were in effect > would indeed be quite a headache.
Probably. One possibility would be to track the table definition on an XID basis and compare that info to the XMIN of a given row; that would allow you to know exactly what the state of the table columns was. But there's still a lot of pitfalls with that, such as VACUUM FREEZE. Since ALTER TABLE on a very large table can be such a nightmare maybe some day this will happen, but I'm not holding my breath. -- Jim C. Nasby, Sr. Engineering Consultant [EMAIL PROTECTED] Pervasive Software http://pervasive.com work: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461 ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
