Re: Assert failure on running a completed portal again

I wrote:
> Don't like this much. I'm not sure I believe any part of this
> approach to deciding whether the portal is "run once". In any
> case, a proper fix for this needs to include actually documenting
> what that field means and does.

After looking at this further, I think this whole "run_once"
business is badly designed, worse documented, and redundant
(as well as buggy). It can be replaced with three self-contained
lines in ExecutePlan, as per the attached.

(Obviously, the API changes in this wouldn't do for the back
branches. But we could leave those arguments in place as
unused dummies.)

regards, tom lane