Re: [HACKERS] postgres_fdw bug in 9.6

Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> writes:
> (2018/01/16 1:47), Robert Haas wrote:
>> Hmm, I was thinking that bar and baz wouldn't be constrained to return
>> just one tuple in that case, but I'm wrong: there would just be one
>> tuple per relation in that case. However, that would also be true for
>> a full join, wouldn't it?

> Consider:

> postgres=# create table bar (a int, b text);
> postgres=# create table baz (a int, b text);
> postgres=# insert into bar values (1, 'bar');
> postgres=# insert into baz values (2, 'baz');
> postgres=# select * from bar full join baz on bar.a = baz.a;
> a | b | a | b
> ---+-----+---+-----
> 1 | bar | |
> | | 2 | baz
> (2 rows)

> Both relations have one tuple, but the full join produces two join
> tuples. I think it would be possible that something like this happens
> when executing a local join plan for a foreign join that performs a full
> join remotely.

Doesn't really matter though, does it? Each of those join rows will
be processed as a separate EPQ event.

regards, tom lane