Re: Performance degradation of REFRESH MATERIALIZED VIEW

On Tue, Apr 27, 2021 at 8:07 AM Andres Freund <andres@anarazel.de> wrote:
>
> Hi,
>
> On 2021-04-26 23:59:17 +0200, Tomas Vondra wrote:
> > On 4/26/21 9:27 PM, Andres Freund wrote:
> > > On 2021-04-26 15:31:02 +0200, Tomas Vondra wrote:
> > > > I'm not sure what to do about this :-( I don't have any ideas about how to
> > > > eliminate this overhead, so the only option I see is reverting the changes
> > > > in heap_insert. Unfortunately, that'd mean inserts into TOAST tables won't
> > > > be frozen ...
> > >
> > > ISTM that the fundamental issue here is not that we acquire pins that we
> > > shouldn't, but that we do so at a much higher frequency than needed.
> > >
> > > It's probably too invasive for 14, but I think it might be worth exploring
> > > passing down a BulkInsertState in nodeModifyTable.c's table_tuple_insert() iff
> > > the input will be more than one row.
> > >
> > > And then add the vm buffer of the target page to BulkInsertState, so that
> > > hio.c can avoid re-pinning the buffer.
> > >
> >
> > Yeah. The question still is what to do about 14, though. Shall we leave the
> > code as it is now, or should we change it somehow? It seem a bit unfortunate
> > that a COPY FREEZE optimization should negatively influence other (more)
> > common use cases, so I guess we can't just keep the current code ...
>
> I'd suggest prototyping the use of BulkInsertState in nodeModifyTable.c
> and see whether that fixes the regression.

Is this idea to have RelationGetBufferForTuple() skip re-pinning
vmbuffer? If so, is this essentially the same as the one in the v3
patch?

Regards,

-- 
Masahiko Sawada
EDB:  https://www.enterprisedb.com/