Re: Reduce "Var IS [NOT] NULL" quals during constant folding

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> However, I'm a bit concerned about the overall premise of the patch
> set. It feels like it is moving something that really ought to happen
> at optimization time back to parse time. I have a feeling that's going
> to break something, although I am not sure right now exactly what.

Ugh, no, that is *completely* unworkable. Suppose that the user
does CREATE VIEW, and the parse tree recorded for that claims that
column X is not-nullable. Then the user drops the not-null
constraint, and then asks to execute the view. We'll optimize on
the basis of stale information.

The way to make this work is what I said before: move the planner's
collection of relation information to somewhere a bit earlier in
the planner. But not to outside the planner.

regards, tom lane