"Norman J. Clarke" <norman@combimatrix.com> writes:
> However, on update to the larger (100k+)columns, the postgres backend
> crashes and dumps core. I've included a backtrace from the core file.
This looks entirely irrelevant to either TOAST or update; I think it is
the known 7.1.1 bug with SELECTs that return no rows in plpgsql.
Try 7.1.2.
regards, tom lane