On Tue, Jul 01, 2008 at 08:27:32AM -0700, Shahaf Abileah wrote:
> Also, in certain situations you might be able to run the alter command
> on each of the slaves and then on the master.  E.g. if you're adding a
> new column that allows null values, then it might be possible to alter
> the slaves even while rows are being inserted into the master.  You will
> still be taking a lock on the table while altering it, but at least
> you're not locking multiple tables at a time across multiple machines.
> Not sure if this is recommended practice.

it's not recommended, but it works.
you add column on slave, then run this on master:
UPDATE pg_trigger SET tgargs=substring(tgargs for octet_length(tgargs)-1)||E'v\\000' where tgname = 'TRIGGER_NAME';
and then add the column on master.

best regards,

depesz