Re: inherit support for foreign tables

In addition to an issue pointed out recently by Horiguchi-san, I've
found there is another issue we have to discuss.  That is, we can't
build any parameterized Append paths for an inheritance tree that
contains at least one foreign table, in set_append_rel_pathlist().  This
is because the patch doesn't take into consideration
"reparameterization" for paths for a foreign table, which attempts to
modify these paths to have greater parameterization so that each child
path in the inheritance tree can have the exact same parameterization.
To do so, I think we would need to add code for the foreign-table case
to reparameterize_path().  And I think we should introduce a new FDW
routine, say ReparameterizeForeignPath() because the processing would be
performed best by the FDW itself.

Comments are welcome!

Thanks,

Best regards,
Etsuro Fujita