Re: [GENERAL] sequences and currval()

On Mon, Jun 02, 2008 at 11:55:14AM -0400, Michael P. Soulier wrote:
> Hello,
>
> I'm migrating a db schema in an automated fashion, using this
>
> UPDATE clients_client
> SET icp_id = null
> WHERE icp_id = 1;
> UPDATE icps_icp
> SET id = nextval('public.icps_icp_id_seq')
> WHERE id = 1;
> UPDATE clients_client
> SET icp_id = currval('public.icps_icp_id_seq')
> WHERE icp_id = null;

Your problem is that this should be: WHERE icp_id IS NULL.

> I've noticed this on a fresh pgsql session.
>
> tugdb=# select currval('icps_icp_id_seq');
> ERROR: currval of sequence "icps_icp_id_seq" is not yet defined in this
> session
>
> I don't understand this, as I only want the current value of the
> sequence. I suppose I can get it this way

currval() returns the value last returned by nextval() *in this
session*. If you havn't called it in this session ofcourse it won't
work. This is for transaction safety.

Have a nice day,
--
Martijn van Oosterhout <kleptog@svana.org>

http://svana.org/kleptog/
> Please line up in a tree and maintain the heap invariant while
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