Re: [HACKERS] Block level parallel vacuum - Mailing list pgsql-hackers

On Tue, 28 Jan 2020 at 12:32, Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Tue, Jan 28, 2020 at 12:04 PM Mahendra Singh Thalor
> <mahi6run@gmail.com> wrote:
> >
> > On Tue, 28 Jan 2020 at 08:14, Amit Kapila <amit.kapila16@gmail.com> wrote:
> > >
> > > On Tue, Jan 28, 2020 at 2:13 AM Mahendra Singh Thalor
> > > <mahi6run@gmail.com> wrote:
> > > >
> > > > On Sat, 25 Jan 2020 at 12:11, Amit Kapila <amit.kapila16@gmail.com> wrote:
> > > > >
> > > > > On Fri, Jan 24, 2020 at 4:58 PM Mahendra Singh Thalor
> > > > > <mahi6run@gmail.com> wrote:
> > > > > >
> > > > > > On Thu, 23 Jan 2020 at 15:32, Mahendra Singh Thalor <mahi6run@gmail.com> wrote:
> > > > > > >
> > > > > > > On Wed, 22 Jan 2020 at 12:48, Masahiko Sawada
> > > > > > > <masahiko.sawada@2ndquadrant.com> wrote:
> > > > > > > >
> > > > > > > > Attached the updated version patch.
> > > > > > >
> > > > > > > Thanks Sawada-san for the re-based patch.
> > > > > > >
> > > > > > > I reviewed and tested this patch.  Patch looks good to me.
> > > > > >
> > > > > > As offline, suggested by Amit Kapila, I verified vacuumdb "-P" option
> > > > > > functionality with older versions(<13) and also I tested vacuumdb by
> > > > > > giving "-j" option with "-P". All are working as per expectation and I
> > > > > > didn't find any issue with these options.
> > > > > >
> > > > >
> > > > > I have made few modifications in the patch.
> > > > >
> > > > > 1. I think we should try to block the usage of 'full' and 'parallel'
> > > > > option in the utility rather than allowing the server to return an
> > > > > error.
> > > > > 2. It is better to handle 'P' option in getopt_long in the order of
> > > > > its declaration in long_options array.
> > > > > 3. Added an Assert for server version while handling of parallel option.
> > > > > 4. Added a few sentences in the documentation.
> > > > >
> > > > > What do you guys think of the attached?
> > > > >
> > > >
> > > > I took one more review round.  Below are some review comments:
> > > >
> > > > 1.
> > > > -P, --parallel=PARALLEL_DEGREE  do parallel vacuum
> > > >
> > > > I think, "do parallel vacuum" should be modified. Without specifying -P, we are still doing parallel vacuum so
wecan use like "degree for parallel vacuum"
 
> > > >
> > >
> > > I am not sure if 'degree' makes it very clear.  How about "use this
> > > many background workers for vacuum, if available"?
> >
> > If background workers are many, then automatically, we are using them(by default parallel vacuum). This option is
toput limit on background workers(limit for vacuum workers) to be used by vacuum process.
 
> >
>
> I don't think that the option is just to specify the max limit because
> that is generally controlled by guc parameters.  This option allows
> users to specify the number of workers for the cases where he has more
> knowledge about the size/type of indexes.  In some cases, the user
> might be able to make a better decision and that was the reason we
> have added this option in the first place.
>
> > So I think, we can use "max parallel vacuum workers (by default, based on no. of indexes)" or "control parallel
vacuumworkers"
 
> >
>
> Hmm, I feel what I suggested is better because of the above explanation.

Agreed.

-- 
Thanks and Regards
Mahendra Singh Thalor
EnterpriseDB: http://www.enterprisedb.com