Hi, 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. Will look into the patch after returning from PGCon, unless somebody wants to. Best regards, Etsuro Fujita
