Re: [HACKERS] postgres_fdw bug in 9.6

Etsuro Fujita <fujita.etsuro@lab.ntt.co.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