Date: Tue, 17 Mar 2020 16:34:26 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: Andres Freund <andres@anarazel.de>,
	Masahiko Sawada <masahiko.sawada@2ndquadrant.com>,
	David Rowley <dgrowleyml@gmail.com>,
	Tomas Vondra <tomas.vondra@2ndquadrant.com>,
	Amit Kapila <amit.kapila16@gmail.com>,
	Masahiko Sawada <sawada.mshk@gmail.com>,
	Darafei =?utf-8?Q?Kom=D1=8Fpa?= Praliaskouski <me@komzpa.net>,
	pgsql-hackers@lists.postgresql.org,
	Alvaro Herrera <alvherre@2ndquadrant.com>,
	Michael Banck <mbanck@gmx.net>
Subject: Re: Berserk Autovacuum (let's save next Mandrill)
Message-ID: <20200317213426.GB26184@telsasoft.com>
References: <20200316201315.dgkeedl6rp2wdjje@alap3.anarazel.de>
 <19be41199e7b303bbecc1066bd9f011d95882aa8.camel@cybertec.at>
 <20200316213459.kh6xln3z35hgjodd@alap3.anarazel.de>
 <7c132215f0e947af7d9ccb7a340ad6e81b369c24.camel@cybertec.at>
 <20200317152409.GW26184@telsasoft.com>
 <e0b452925b00e2712e299a3370f85ee6be32889c.camel@cybertec.at>
 <20200317195616.GZ26184@telsasoft.com>
 <ade9403df7c3051ad68b58e98710c408511a4491.camel@cybertec.at>
 <20200317210702.GA26184@telsasoft.com>
 <8b67057b658638936abc125382398c143da4397c.camel@cybertec.at>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <8b67057b658638936abc125382398c143da4397c.camel@cybertec.at>
User-Agent: Mutt/1.9.4 (2018-02-28)
Precedence: bulk

On Tue, Mar 17, 2020 at 10:22:44PM +0100, Laurenz Albe wrote:
> On Tue, 2020-03-17 at 16:07 -0500, Justin Pryzby wrote:
> > > Assume a scale factor >= 1, for example 2, and n live tuples.
> > > The table has just been vacuumed.
> > > 
> > > Now we insert m number tuples (which are live).

.. but not yet counted in reltuples.

On Tue, Mar 17, 2020 at 10:22:44PM +0100, Laurenz Albe wrote:
> Note that this is different from autovacuum_vacuum_scale_factor,
> because inserted tuples are live, while dead tuples are not.

But they're not counted in reltuples until after the next vacuum (or analyze),
which is circular, since it's exactly what we're trying to schedule.

                reltuples = classForm->reltuples;
                vactuples = tabentry->n_dead_tuples;
+               instuples = tabentry->inserts_since_vacuum;
                anltuples = tabentry->changes_since_analyze;
 
                vacthresh = (float4) vac_base_thresh + vac_scale_factor * reltuples;
+               vacinsthresh = (float4) vac_ins_base_thresh + vac_ins_scale_factor * reltuples;

-- 
Justin