Duplicate object names in GRANT

Hi all,

I ran across this yesterday on HEAD:

template1=# grant select on foo, foo to swm;
ERROR: tuple already updated by self

We could do away with the error by producing a unique list of object names
-- but that would impose an extra cost on the common case. It seems to me
that producing a useful error message would entail the same cost, however.

Thoughts?

Gavin