Re: ALTER TABLE ... NOREWRITE option

>> I'm not thrilled about inventing YA keyword for this.  If you have a
>> problem with that sort of scenario, why aren't you testing your DDL
>> on a test server before you do it on production?

*I* do test my DDL.  However, there are literally hundreds of thousands
of Rails, Django and Hibernate developers who "test" their DDL by
running it using a 5-row dataset on their laptops before pushing it to
production.  As far as these folks are concerned, "rewrite if there's a
default" is a completely unintuitive booby-trap.

I agree that adding "NOREWRITE" is a bad solution, though.  Personally,
I'd rather have a system function which tests whether a series of DDL
statements involves a rewrite anywhere.  e.g.:

SELECT pg_test_for_rewrite('ALTER TABLE josh ADD COLUMN haircolor')

Hmmmm.  Actually, that wouldn't work with migrations tools, especially
Rails.  Better, what about a GUC?

SET message_on_rewrite=WARNING;

-- 
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com