On Wed, Dec 24, 2008 at 6:41 PM, Erik Jones <ejo...@engineyard.com> wrote: > > On Dec 24, 2008, at 12:04 PM, Grzegorz Jaśkiewicz wrote: > >> On Wed, Dec 24, 2008 at 6:12 PM, Erik Jones <ejo...@engineyard.com> wrote: >>> >>> Yes, and columns have default values, too, which are not tied to their >>> datatype's default value (if it even has one). ALTER TABLE initializes >>> rows >>> to have the new *column's* default. A column of some domain type could >>> easily have some default other than the domain's default and, in fact, if >>> you don't specify a default for the column then it's default is NULL. >> >> the whole thing about domains, is that you specify type and default, >> and even check constraint. And I did specify default - hence I would >> expect it to be set to that value!! > > You really need to understand the difference between a domain's default and > a column's default. The ALTER TABLE docs specifically say that if you don't > specify a default for the new *column* then that column is set to NULL for > all rows. That is not the same as not providing a value for a column of > some domain type with a default in an INSERT statement. A domain with a > default does not specify that it can not be set to null:
I disagree. It's quite natural and reasonable to have defaults passed through the composite type as the OP expects. This is a possible improvement (TODO?) in the way composite types are handled. There are a couple of other loopholes in domans/composite types: * domains can't be stacked in an array (but you can if they are wrapped in a composite type) * check constraints not enforced for composite type on cast (but are for domains) * alter type should be expanded to allow things that are currently possible via alter table (currently a TODO, IIRC), or create table/alter table should be adjusted for better handling of types, and 'create type as' should be deprecated. The latter is what I think should happen, but it's controversial :-). In the meantime the OP has to decide what he wants to use more, composite types or default values on domains. merlin -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
