Re: Postgres unique index checking and atomic transactions

On 24 Jul 2003, Greg Stark wrote:

>
> So I have to adjust a primary key by adding one to every existing record.
> Obviously this isn't a routine operation, my data model isn't that messed up.
> It's a one-time manual operation.
>
> However when I tried to do the equivalent of:
>
> update tab set pk = pk + 1
>
> I got
>
> ERROR: Cannot insert a duplicate key into unique index tab_pkey
>
> Is that right? Obviously after completing the query there would be no
> duplicate keys. Is this a case where I would need deferred constraints to
> allow this? Even for immediate constraints shouldn't a single sql update be
> able to go ahead as long as it leaves things in a consistent state?

I've run into this before. If your pks are in the range of say 1 to 1000,
then just add 50000 to them, then subtract 49999...