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

On Wed, Mar 25, 2015 at 9:51 PM, Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com> wrote:
> 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?
>
> 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?

A few random cosmetic problems:

- The hunk in allpaths.c is useless.
- The first hunk in fdwapi.h contains an extra space before the
closing parenthesis.

And then:

+ else if (scan->scanrelid == 0 &&
+ (IsA(scan, ForeignScan) || IsA(scan, CustomScan)))
+ varno = INDEX_VAR;

Suppose scan->scanrelid == 0 but the scan type is something else? Is
that legal? Is varno == 0 the correct outcome in that case?

More later.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company