Re: Custom/Foreign-Join-APIs (Re: [v9.5] Custom Plan API)

2015/03/26 10:51、Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com> のメール：
> The attached patch adds GetForeignJoinPaths call on make_join_rel() only when
> 'joinrel' is actually built and both of child relations are managed by same
> FDW driver, prior to any other built-in join paths.
> I adjusted the hook definition a little bit, because jointype can be reproduced
> using SpecialJoinInfo. Right?

OK.

>
> Probably, it will solve the original concern towards multiple calls of FDW
> handler in case when it tries to replace an entire join subtree with a foreign-
> scan on the result of remote join query.
>
> How about your opinion?

Seems fine. I’ve fixed my postgres_fdw code to fit the new version, and am working on handling a whole-join-tree.

It would be difficult in the 9.5 cycle, but a hook point where we can handle whole joinrel might allow us to optimize a query which accesses multiple parent tables, each is inherited by foreign tables and partitioned with identical join key, by building a path tree which joins sharded tables first, and then union those results.

--
Shigeru HANADA
shigeru(dot)hanada(at)gmail(dot)com