Re: BUG #14770: postgres_fdw assumes foreign table is in postgres

rbiro(at)interfacefinancial(dot)com writes:
> Using postgres_fdw seems to assume that the foreign table is not also a
> foreign table in the remote db.

> Symptoms: connections closing with little or no error message, requesting
> ctid from a foreign table that doesn't have a ctid, even dataloss iin one
> instance*.

> Reproduce: create two Postgresql databases, a and b. Create a foreign table
> in a using a fdw other than postgres_fdw. Multicorn is a good choice since
> it is then easy to see everything.

Without a concrete test case, it's really hard to prove anything about
this, or even to tell which component the problem is in. But a desultory
test using two levels of postgres_fdw seemed to work, which suggests that
you need to take this up with the multicorn authors.

contrib_regression=# create table base (a int, b text);
CREATE TABLE
contrib_regression=# create foreign table level1 (a int, b text)
server loopback options(schema_name 'public', table_name 'base');
CREATE FOREIGN TABLE
contrib_regression=# create foreign table level2 (a int, b text)
server loopback options(schema_name 'public', table_name 'level1');
CREATE FOREIGN TABLE
contrib_regression=# insert into level2 values(42, 'foo');
INSERT 0 1
contrib_regression=# select * from base;
a | b
----+-----
42 | foo
(1 row)
contrib_regression=# update level2 set b = 'bar' where a = 42;
UPDATE 1
contrib_regression=# select * from base;
a | b
----+-----
42 | bar
(1 row)

regards, tom lane