Re: improve join_collapse_limit docs

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
> This should include some weasel-wording along the lines of "At
> present, blah blah blah".

Good point, thanks.

> It is theoretically legal to reorder outer joins in some cases

Indeed; see "Outerjoin Simplification and Reordering for Query
Optimization" by Gelindo-Legaria and Rosenthal (ACM TDS, Vol. 22,
No. 1, March 1997, Pages 43-74), for example.

> I harbor ambitions of teaching the planner about that sooner or
> later.

Indeed, I've speculated about doing this myself at some indeterminate
point in the future. Of course (a) your knowledge of the optimizer
dwarfs my own by several orders of magnitude (b) I don't have any firm
plans to do this, it just looked like an interesting problem. So
please don't let me stop you implementing this yourself at your
leisure.

I've fixed the other minor points you raised and applied the patch --
thanks for the feedback.

-Neil