Re: Serial Data Type

On Wed, Apr 2, 2008 at 10:12 PM, Naz Gassiep <naz@mira.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;