I wrote:
> On balance I think we ought to switch to set-all-the-columns, though
> only in 9.3+ --- a back-patched behavioral change doesn't seem like a
> good idea.
And here is a draft patch for that. I was interested to find that the
documentation already claims that all columns are set in the relevant
cases (so the docs changes here are just wordsmithing and
clarification).
regards, tom lane