Horton

Re: Berserk Autovacuum (let's save next Mandrill)

David Rowley <dgrowleyml@gmail.com>

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From: David Rowley <dgrowleyml@gmail.com>
To: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: Andres Freund <andres@anarazel.de>, Alexander Korotkov <a.korotkov@postgrespro.ru>, Justin Pryzby <pryzby@telsasoft.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Masahiko Sawada <masahiko.sawada@2ndquadrant.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Amit Kapila <amit.kapila16@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Darafei Komяpa Praliaskouski <me@komzpa.net>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Michael Banck <mbanck@gmx.net>
Date: 2020-03-27T22:59:07Z
Lists: pgsql-hackers 
On Fri, 27 Mar 2020 at 22:40, Laurenz Albe <laurenz.albe@cybertec.at> wrote:
> The new meaning of -2 should be documented, other than that it looks
> good to me.

But the users don't need to know anything about -2. It's not possible
to explicitly set the value to -2. This is just the reset value of the
reloption which means "use the GUC".

> I'll accept the new semantics, but they don't make me happy.  People are
> used to -1 meaning "use the GUC value instead".

The problem with having -1 on the reloption meaning use the GUC, in
this case, is that it means the reset value of the reloption must be
-1 and we need to allow them to set -2 explicitly, and if we do that,
then -1 also becomes a valid value that users can set. Maybe that's
not the end of the world, but I'd rather have the reset value be
unsettable by users. To me, that's less confusing as there are fewer
special values to remember the meaning of.

The reason I want a method to explicitly disable the feature is the
fact that it's easy to document and it should reduce the number of
people who are confused about the best method to disable the feature.
I know there's going to be a non-zero number of people who'll want to
do that.

Commits

  1. Further improve stability fix for partition_aggregate test.

  2. Improve stability fix for partition_aggregate test.

  3. Attempt to stabilize partitionwise_aggregate test

  4. Fix race condition in statext_store().

  5. Attempt to fix unstable regression tests, take 2

  6. Attempt to fix unstable regression tests

  7. Trigger autovacuum based on number of INSERTs

  8. Fix upper limit for vacuum_cleanup_index_scale_factor