MIME-Version: 1.0
References: 
 <CACG=ezZOrNsuLoETLD1gAswZMuH2nGGq7Ogcc0QOE5hhWaw=cw@mail.gmail.com>
 <CAD21AoCdx5ZNS_cO7bYz1Zfb+Kw1kuJV2wtewrz7T1pPpjcWGw@mail.gmail.com>
 <CAJDiXgi6ZQOoSEqj9RyZMEh+HHBtmW0+PHD85UNPtKch8ubvdg@mail.gmail.com>
 <CAD21AoBcoA-i-pJ_=y+jg14R8_QaJA1iwktCnu5i-C=yXDFPdA@mail.gmail.com>
 <CAJDiXgjnUdE6Sk4M0unmT+9dULyFAxcum2txQKpWTuo4uQ_oXQ@mail.gmail.com>
 <CAD21AoBTZdVR93JBo620B=MX-K8cdm3VRbjrBr_Vcpngk3AjVw@mail.gmail.com>
 <CAA5RZ0vfBg=c_0Sa1Tpxv8tueeBk8C5qTf9TrxKBbXUqPc99Ag@mail.gmail.com>
 <CAD21AoBgvUeWS8ZsXBahA1XdYayK6DJ6dx49d6Xpii-iH+Hrwg@mail.gmail.com>
 <CAA5RZ0vF+Lr-jU1LAZWTGUjboUETk8oLvaNBbA5ozX6dau+how@mail.gmail.com>
 <CAJDiXggueLSGMNRmLshbmFRfbo4jzks0W8bLDfUSRZ-61fPVEQ@mail.gmail.com>
 <CAFY6G8cJ=DRTX75pOGerH6sk39dRt+7MSH+y_qppDdhPs=qdQA@mail.gmail.com>
 <CAJDiXgg1t6wk9NjyMUTm1iKqM9GtdQ_wrEchBtz3xjWBZM8W8A@mail.gmail.com>
 <CAD21AoAC0=Xi38RQcAO4A+vdmoXToZMoHfbS=KLT49fAOTH_gA@mail.gmail.com>
 <CAJDiXgiD+AZKhJSn-FSRVQxtDLmJd95wDu4wtKniQF5==1JcjQ@mail.gmail.com>
 <CAD21AoAM8KsqNhrZYJuf7odvxcTC0TumXazJc-r_wC5KnDFDPg@mail.gmail.com>
 <CAJDiXghbcOC9OOj3ampxuyqXH0geggnosnrYUHGygkpss-RtxA@mail.gmail.com>
 <CAD21AoAPnq0vrcGgeN++r1GoL8Kza7jaGL=TNzuBn6+MkR=rUQ@mail.gmail.com>
 <CAJDiXghmsbTmnm--9B5bbuZXa1OL7SZ0HYppX3tx9XsdwfJBhA@mail.gmail.com>
 <DB3C67FCRLOO.1R5NLYCNEA6BF@gmail.com>
 <CAJDiXgiYiX+azuR76DcVx8fZn57m_4v6cB14-GW34mWa=qudFQ@mail.gmail.com>
 <CAD21AoDtPpkkQ_h1yf4oTx1qn4SRdTeVY3qs+9J07fYqa_4Gww@mail.gmail.com>
 <CAJDiXgi7KB7wSQ=Ux=ngdaCvJnJ5x-ehvTyiuZez+5uKHtV6iQ@mail.gmail.com>
 <CAD21AoCcHKKXsr9Oh736ejckqqS1i430xGEyJ=JP5OL0ExyP1A@mail.gmail.com>
 <CAJDiXghaFT_1sSv3q8mjyZ_RLZDgiogg0mWRvLxSWvkUi2CcLg@mail.gmail.com>
 <CAA5RZ0u63W41OmcEO+HLs4CSo-Sd3J+Q-4=04iud8V=xX4iUrA@mail.gmail.com>
 <CAJDiXgin1TXniVGJKzOTA=F9K342uVfm6O0EmubTVB=F+XSrbA@mail.gmail.com>
 <CAD21AoDadzAwibxf-+urjx=XL+eVu8=Ut-Lh2GxXUt32LbPG3Q@mail.gmail.com>
 <CAD21AoD6HhraqhOgkQJOrr0ixZkAZuqJRpzGv-B+_-ad6d5aPw@mail.gmail.com>
 <CAJDiXgiGSpqMQSOx-cVO_LtcB5GWHBy9ph7oOR4ebbX8A==kgw@mail.gmail.com>
 <CAD21AoBRRXbNJEvCjS-0XZgCEeRBzQPKmrSDjJ3wZ8TN28vaCQ@mail.gmail.com>
 <CAPpHfduBJfMcojvmYHUo8b_C=0cxRy1N+tNiNGoA3RAZq2ApaA@mail.gmail.com>
 <CAD21AoC82NeHKXc965pPUZO2eyo1U7P6cmfRJbrcPDcnd7_6hw@mail.gmail.com>
 <CAJDiXghP2kXnEz+cj3rAWNM3NdKSB_4WtnngFXpVz2omPhGr5A@mail.gmail.com>
 <CAD21AoA0bnRZC_OqKMnH-Ln+OZ9z9k56j2c_MXj8pw69O-wkBw@mail.gmail.com>
 <CAA5RZ0sSXDza7_nUUbhHL_Sws+M+HR1daKJPXHpdLuNCkwUgUg@mail.gmail.com>
 <CAJDiXggrBsbzOisf+Nu8pZkYGrpUZaFbosL1Wbm3kKxzTm4xgw@mail.gmail.com>
In-Reply-To: 
 <CAJDiXggrBsbzOisf+Nu8pZkYGrpUZaFbosL1Wbm3kKxzTm4xgw@mail.gmail.com>
From: Sami Imseih <samimseih@gmail.com>
Date: Sat, 22 Nov 2025 16:51:42 -0600
Message-ID: 
 <CAA5RZ0tbiPcgQEjnhdnjz6qSjfRsGrr8jGCaMcrMaoPpax3wig@mail.gmail.com>
Subject: Re: POC: Parallel processing of indexes in autovacuum
To: Daniil Davydov <3danissimo@gmail.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>,
 Alexander Korotkov <aekorotkov@gmail.com>,
	Matheus Alcantara <matheusssilv97@gmail.com>,
 Maxim Orlov <orlovmg@gmail.com>,
	Postgres hackers <pgsql-hackers@lists.postgresql.org>
Content-Type: text/plain; charset="UTF-8"
Archived-At: 
 <https://www.postgresql.org/message-id/CAA5RZ0tbiPcgQEjnhdnjz6qSjfRsGrr8jGCaMcrMaoPpax3wig%40mail.gmail.com>
Precedence: bulk

> > nworkers has a double meaning. The return value of
> > AutoVacuumReserveParallelWorkers
> > is nreserved. I think this should be
> >
> > ```
> > nreserved = AutoVacuumReserveParallelWorkers(nworkers);
> > ```
> >
> > and nreserved becomes the authoritative value for the number of parallel
> > workers after that point.

I could not find this pattern being used in the code base.
I think it will be better and more in-line without what we generally do
and pass-by-reference and update the value inside
AutoVacuumReserveParallelWorkers:

```
AutoVacuumReserveParallelWorkers(&nworkers).
```

Maybe that's just my preference.

>> ---
>> { name => 'autovacuum_max_parallel_workers', type => 'int', context =>
>> 'PGC_SIGHUP', group => 'VACUUM_AUTOVACUUM',
>>   short_desc => 'Maximum number of parallel autovacuum workers, that
>> can be taken from bgworkers pool.',
>>   long_desc => 'This parameter is capped by "max_worker_processes"
>> (not by "autovacuum_max_workers"!).',
>>   variable => 'autovacuum_max_parallel_workers',
>>   boot_val => '0',
>>   min => '0',
>>   max => 'MAX_BACKENDS',
>> },
>>
>> Parallel vacuum in autovacuum can be used only when users set the
>> autovacuum_parallel_workers storage parameter. How about using the
>> default value 2 for autovacuum_max_parallel_workers GUC parameter?

> Sounds reasonable, +1 for it.

v15-0004 has an incorrect default value for `autovacuum_max_parallel_workers`.
It should now be 2.

+          Sets the maximum number of parallel autovacuum workers that
+          can be used for parallel index vacuuming at one time. Is capped by
+          <xref linkend="guc-max-worker-processes"/>. The default is 0,
+          which means no parallel index vacuuming.

--
Sami