Re: Copy-pasto in the ExecForeignDelete documentation

On 2016/02/04 0:13, Robert Haas wrote:
> On Mon, Feb 1, 2016 at 5:26 AM, Etsuro Fujita
> <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
>> I don't think the data is referenced by the AFTER ROW DELETE triggers.

> Why do you think that? And why would DELETE triggers be different
> from UPDATE triggers, which do something similar?

As for the UPDATE case, I think local AFTER ROW UPDATE triggers have to
reference the data since a BEFORE trigger on the remote server might
change the to-be-updated version of the row originally assigned. But as
for the DELETE case, I was not thinking so.

> I looked up the history of this code and it was introduced in
> 7cbe57c3, which added support for triggers on foreign tables. Noah
> did that commit and he's rarely wrong about stuff like this, so I
> suspect you may be missing something. One thing to consider is
> whether the version of the row that finally gets deleted is
> necessarily the same as the version originally selected from the
> remote side; e.g. suppose the remote side has triggers, too.

Maybe I'm missing something, but I was thinking that version should be
the same as the version originally selected from the remote server; the
delete would be otherwise discarded since the updated version would not
satisfy the delete's condition, something similar to "ctid = $1" in the
postgres_fdw case, during an EvalPlanQual-like recheck on the remote server.

Best regards,
Etsuro Fujita