Robert Haas <robertmh...@gmail.com> writes: > On Thu, Mar 15, 2018 at 11:01 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> It might be worth looking at whether we couldn't fix the single-member- >> Append issue the same way we fix no-op SubqueryScans, ie let setrefs.c >> get rid of them. That's not the most beautiful solution perhaps, but >> it'd be very localized and low-risk.
> That's definitely a thought; it's a probably the simplest way of > saving the run-time cost of the Append node. However, I don't think > it's a great solution overall because it doesn't get us the other > advantages that David mentions in his original post. I think that to > gain those advantages we'll need to know at path-creation time that > there won't ultimately be an Append node in the finished plan. Meh. We could certainly know that by inspection ("only one child? it'll be history"). I remain of the opinion that this is a big patch with a small patch struggling to get out. regards, tom lane