Re: Expression errors with "FOR UPDATE" and postgres_fdw with partition wise join enabled.

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Thu, Aug 2, 2018 at 4:25 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Now, that's a bit of a problem for postgres_fdw, because it seems to
>> insist on injecting WRVs even when the query text does not require any.
>> Why is that, and can't we get rid of it?

> I don't quite know what you mean here -- postgres_fdw does use
> whole-row vars for EPQ handling, which may be what you're thinking
> about.

As far as I can see from the example that started this thread,
postgres_fdw injects WRVs into a PWJ whether or not the query involves
FOR UPDATE; that's why this bug is reproducible in a query without FOR
UPDATE. But we shouldn't need any EPQ support in that case.

> Honestly, I'm pretty impressed that we have added not one but two
> members to the RelOptKind enum without as little collateral damage as
> there has been.

Color me a bit more skeptical about the bug density in that, given
that enable_partitionwise_join is off by default; that means you're
not getting a lot of testing.

regards, tom lane