Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> I present a patch to allow READ UNCOMMITTED that is simple, useful and
> efficient.
Won't this break entirely the moment you try to read a tuple containing
toasted-out-of-line values? There's no guarantee that the toast-table
entries haven't been vacuumed away.
I suspect it can also be broken by cases involving, eg, dropped columns.
There are a lot of assumptions in the system that no one will ever try
to read dead tuples.
The fact that you can construct a use-case in which it's good for
something doesn't make it safe in general :-(
regards, tom lane