Re: WIP: Upper planner pathification

The basic point of this patch is to apply the generate-and-compare-Paths
paradigm to the planning steps after query_planner(), which only covers

...
> The present patch addresses this problem by inventing Path nodes to
> represent every post-scan/join step

I'm really glad to see that. Separating path nodes for later steps opens a new ways to optimize queries. For first glance, consider
select * from a left outer join b on a.i = b.i limit 1;
Limit node could be pushed down to scan over 'a' table if b.i is unique.

--
Teodor Sigaev                                   E-mail: teodor@sigaev.ru
                                                   WWW: http://www.sigaev.ru/

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