Re: inherit support for foreign tables

Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> writes:
> Could you guess any use cases in which we are happy with ALTER
> TABLE's inheritance tree walking? IMHO, ALTER FOREIGN TABLE
> always comes with some changes of the data source so implicitly
> invoking of such commands should be defaultly turned off. If the
> ALTER'ing the whole familiy is deadfully useful for certain
> cases, it might be explicitly turned on by some syntax added to
> CREATE FOREIGN TABLE or ALTER TABLE.

> It would looks like following,

> CREATE FOREIGN TABLE ft1 () INHERITS (pt1 ALLOW_INHERITED_ALTER, pt2);

> ALTER TABLE INCLUDE FOREIGN CHILDREN parent ADD COLUMN add1 integer;

Ugh. This adds a lot of logical complication without much real use,
IMO. The problems that have been discussed in this thread are that
certain types of ALTER are sensible to apply to foreign tables and
others are not --- so how does a one-size-fits-all switch help that?

Also, there are some types of ALTER for which recursion to children
*must* occur or things become inconsistent --- ADD COLUMN itself is
an example, and ADD CONSTRAINT is another. It would not be acceptable
for an ALLOW_INHERITED_ALTER switch to suppress that, but if the
switch is leaky then it's even less consistent and harder to explain.

regards, tom lane