Re: Serial Data Type

On Wed, Apr 2, 2008 at 10:12 PM, Naz Gassiep <naz(at)mira(dot)net> wrote:
> I have just created a table using SELECT INTO however the PK was
> supposed to be a serial. It is now an integer. To make it a serial I
> just create the seq and set the default to be the nextval() of that
> sequence right? is there anything else I need to do? It'll maintain the
> transactional safety of a serial created default, right? I.e., it'll not
> rollback seq values on a transaction abortion will it?
> Thanks,

not quite. you also have to set the sequence to a higher number than
the highest currently inserted key of the table. you do this with
setval...watch out for the is_called property. also you should lock
the table first...otherwise you would get a race if someone inserts a
value into the table between the time when you calculate the value for
setval and you assign it to the sequence.

so (pseudo code here):

begin;
lock table foo;
setval('the_sequence, (select max(foo_id) from foo), true);
alter table foo alter foo_id default nextval('the_sequence');
alter sequence the_sequence owned by foo.foo_id; -- h/t to adam rich
commit;