Tom Lane wrote:
> It looks like you have a stale plan for that ON DELETE SET NULL
> constraint. Was there perhaps an index on operator_id that you removed?
> Postgres is not very good about flushing cached plans when you change
> table schemas (something I hope will be fixed in 8.3).
>
> If that is the problem, starting a fresh session would be enough to take
> care of it.
>
> regards, tom lane
>
>
Thanks Tom. You were, as usual, correct!