On 2018-08-02 16:51:10 -0400, Tom Lane wrote: > Robert Haas <robertmh...@gmail.com> writes: > > [ reasons why DDL under less than AEL sucks ] > > Unfortunately, none of these problems are made to go away with an > AcceptInvalidationMessages at statement start. That just makes the > window smaller. But DDL effects could still be seen - or not - > partway through a statement, with just as much ensuing hilarity > as in your example. Maybe more.
I think it's a lot easier to explain that every newly issued statement sees the effect of DDL, and already running statements may see it, than something else. I don't agree that parse analysis is a good hook to force that, as I've written. > The real issue here, and the reason why I'm very unhappy with the mad rush > in certain quarters to try to reduce locking levels for DDL, is exactly > that it generally results in uncertainty about when the effects will be > seen. I do not think your proposal does much more than put a fig leaf > over that problem. I think it's a significant issue operationally, which is why that pressure exists. I don't know what makes it a "mad rush", given these discussions have been going on for *years*? Greetings, Andres Freund
