Jeff Davis <pgsql(at)j-davis(dot)com> writes:
> There you see a snapshot of the table that never existed. Either the
> snapshot was taken before the UPDATE, in which case i=3 should be
> included, or it was taken after the UPDATE, in which case i=4 should be
> included. So atomicity is broken for WHERE.
This assertion is based on a misunderstanding of what FOR UPDATE in
read-committed mode is defined to do. It is supposed to give you the
latest available rows.
regards, tom lane