Re: serializable read only deferrable

"Kevin Grittner" <Kevin.Grittner@wicourts.gov> writes:
> Attached.
> Accomplished more through mimicry (based on setting transaction
> isolation level) than profound understanding of the code involved;
> but it passes all regression tests on both `make check` and `make
> installcheck-world`.  This includes a new regression test that an
> attempt to change it after a query fails.  I've poked at it with
> various ad hoc tests, and it is behaving as expected in those.

Hmm.  This patch disallows the case of creating a read-only
subtransaction of a read-write parent.  That's a step backwards.
I'm not sure how we could enforce that the property not change
after the first query of a subxact, but maybe we don't care that much?
Do your optimizations pay attention to local read-only in a subxact?
        regards, tom lane