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From: Justin Pryzby <pryzby@telsasoft.com>
To: Julien Rouhaud <rjuju123@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>
Cc: robertmhaas@gmail.com
Cc: pgsql-hackers@postgresql.org
Subject: Re: pg_stat_statements issue with parallel maintenance (Was Re: WAL usage calculation patch)
Date: Sat, 11 Apr 2020 17:33:19 -0500
Message-ID: <20200411223319.GM2228@telsasoft.com> (raw)
In-Reply-To: <20200328151721.GB12854@nol>
References: <20200319153129.GA36079@nol>
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	<a1452be6-9e82-59c4-3c54-b3f8919e75c0@oss.nttdata.com>
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	<20200328133827.GA12854@nol>
	<20200328151721.GB12854@nol>

On Sat, Mar 28, 2020 at 04:17:21PM +0100, Julien Rouhaud wrote:
> On Sat, Mar 28, 2020 at 02:38:27PM +0100, Julien Rouhaud wrote:
> > On Sat, Mar 28, 2020 at 04:14:04PM +0530, Amit Kapila wrote:
> > > 
> > > I see some basic problems with the patch.  The way it tries to compute
> > > WAL usage for parallel stuff doesn't seem right to me.  Can you share
> > > or point me to any test done where we have computed WAL for parallel
> > > operations like Parallel Vacuum or Parallel Create Index?
> > 
> > Ah, that's indeed a good point and AFAICT WAL records from parallel utility
> > workers won't be accounted for.  That being said, I think that an argument
> > could be made that proper infrastructure should have been added in the original
> > parallel utility patches, as pg_stat_statement is already broken wrt. buffer
> > usage in parallel utility, unless I'm missing something.
> 
> Just to be sure I did a quick test with pg_stat_statements behavior using
> parallel/non-parallel CREATE INDEX and VACUUM, and unsurprisingly buffer usage
> doesn't reflect parallel workers' activity.
> 
> I added an open for that, and adding Robert in Cc as 9da0cc352 is the first
> commit adding parallel maintenance.

I believe this is resolved for parallel vacuum in master and parallel create
index back to PG11.

I marked this as closed.
https://wiki.postgresql.org/index.php?title=PostgreSQL_13_Open_Items&diff=34802&oldid=34781

-- 
Justin





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  To: pgsql-hackers@postgresql.org
  Cc: pryzby@telsasoft.com, rjuju123@gmail.com, amit.kapila16@gmail.com, robertmhaas@gmail.com
  Subject: Re: pg_stat_statements issue with parallel maintenance (Was Re: WAL usage calculation patch)
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