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

On Thu, Mar 11, 2021 at 2:22 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> 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.

I can understand that those two settings might interact in some way
that is bad or unintended, but I feel like if I can't understand what
exactly the bad interaction is after reading the commit message,
that's probably a sign that the commit message isn't as clear as it
could be.

--
Robert Haas
EDB: http://www.enterprisedb.com