On Wed, Mar 7, 2012 at 3:49 PM, Merlin Moncure <mmoncure@xxxxxxxxx> wrote: > On Wed, Mar 7, 2012 at 2:31 PM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: >> Merlin Moncure <mmoncure@xxxxxxxxx> writes: >>> On Wed, Mar 7, 2012 at 11:45 AM, Mike Blackwell <mike.blackwell@xxxxxxx> wrote: >>>> alter table a add column even_more_stuff boolean not null default false; >> >>> aha! that's not what you posted last time. you appended 'not null >>> default false'; which inexplicably breaks the ALTER. >> >>> try this: >>> ALTER TABLE a ADD COLUMN even_more_stuff text not null; >>> ALTER TABLE a ALTER even_more_stuff set default false; >>> ALTER TABLE a DROP COLUMN even_more_stuff; >>> ALTER TABLE a ADD COLUMN even_more_stuff boolean not null default false; >> >>> (this really looks like a bug in postgres, cc-ing to bugs) >> >> It is not a bug. The ALTER ADD ... DEFAULT ... form implies rewriting >> every existing tuple of the rowtype to insert a non-null value in the >> added column, and we don't have support for doing that to rowtype >> columns, only to the target table and descendants. > > I'm not buying that..it implies no such thing. In particular, for > table-as-rowtype columns, there's no way that I can see to have > default values be generated. So why does it follow that the dependent > table has to be rewritten? Column constraints are not enforced on the > rowtype, so it follows that default shouldn't be either considering > there's no way to get the default to fire. Composite type (or table > based composite) defaults are applied to the composite as a whole, not > to specific fields. I think Tom's correct about what the right behavior would be if composite types supported defaults, but they don't, never have, and maybe never will. I had a previous argument about this with Tom, and lost, though I am not sure that anyone other than Tom thinks that the current behavior is for the best. But see commits a06e41deebdf74b8b5109329dc75b2e9d9057962 and a40b1e0bf32b1da46c1baa9bc7da87f207cd37d8. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
