Re: pgsql: Don't consider newly inserted tuples in nbtree VACUUM.

On Thu, Mar 11, 2021 at 11:13 AM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Thu, Mar 11, 2021 at 1:57 AM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
> > I think that this commit has some issues that need more thoughts.
>
> My biggest issue with this commit is that I can't understand from the
> commit message why it's a bug fix that deserves to be back-patched. To
> be honest, I can't even really understand whether it's a good idea in
> master.

It is convoluted. The issue that led to my backpatching to 13 was tied
to a 4% - 16% regression in an append-only workload by Mark Callaghan
(he is well known as the main person behind MyRocks at Facebook):

https://smalldatum.blogspot.com/2021/01/insert-benchmark-postgres-is-still.html

Autovacuums driven by autovacuum_vacuum_insert_threshold scan indexes
without receiving any benefit for it. Clearly
vacuum_cleanup_index_scale_factor was misdesigned, but that only
became a real problem with autovacuum_vacuum_insert_threshold. That
did not seem acceptable to me. It'll get worse and worse as you add
more and more indexes.

--
Peter Geoghegan