On Tue, May 28, 2019 at 3:40 PM Etsuro Fujita <etsuro.fuj...@gmail.com> wrote: > On Tue, May 28, 2019 at 12:54 PM Amit Langote > <langote_amit...@lab.ntt.co.jp> wrote: > > On 2019/05/27 22:02, Tom Lane wrote: > > > Amit Langote <langote_amit...@lab.ntt.co.jp> writes: > > >> On 2019/05/27 10:52, Shohei Mochizuki wrote: > > >>> I noticed returning a modified record in a row-level BEFORE UPDATE > > >>> trigger > > >>> on postgres_fdw foreign tables do not work. Attached patch fixes this > > >>> issue. > > >>> This is because current fdw code adds only columns to RemoteSQL that > > >>> were > > >>> explicitly targets of the UPDATE as follows. > > > > > >> Yeah. So, the trigger execution correctly modifies the existing tuple > > >> fetched from the remote server, but those changes are then essentially > > >> discarded by postgres_fdw, that is, postgresExecForeignModify(). > > > > Perhaps, if the table has relevant BEFORE triggers, we should just abandon > > > our attempts to optimize away fetching/storing all columns? It seems like > > > another potential hazard here is a trigger needing to read a column that > > > is not mentioned in the SQL query. > > > So, the only problem here is the optimizing away of storing all columns, > > which the Mochizuki-san's patch seems enough to fix.
Yeah, I think so too, because in UPDATE, we fetch all columns from the remote (even if the target table doesn't have relevant triggers). > Will look into the patch after returning from PGCon, unless somebody wants to. I'll look into the patch more closely tomorrow. Sorry for the delay. As I said in another email today, I felt a bit under the weather last week. Best regards, Etsuro Fujita
