Re: BUG #17812: LOCK TABLE IN ACCESS EXCLUSIVE MODE with a view returns an empty tuple set

"David G. Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> writes:
> Session 4:
> create table tbl2 as select * from view1;
> SELECT 0

> Why is it OK for session 4 to be different here?

Maybe it isn't. The code flow for CREATE TABLE AS is a bit weird
IIRC, and maybe it's missing a step where we should update the
active snapshot.

> It is unclear to me whether you were instead talking about other sessions
> dropping tables as another way of saying "ACCESS EXCLUSIVE" in which case
> at what lock level should this anomaly go away, and does it?

The originally-proposed tests seemed to all involve either TRUNCATE
or DROP TABLE, which are outside what I consider to be our MVCC
guarantees. Your example here does seem a bit strange though.
Views generally ought not have different semantics from writing
out the view query in-line.

regards, tom lane