Reply-To: jesper.pedersen@redhat.com
Subject: Re: pg_upgrade: Pass -j down to vacuumdb
To: "Jamison, Kirk" <k.jamison@jp.fujitsu.com>
Cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>,
 "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>,
 Bruce Momjian <bruce@momjian.us>
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 <2dc5eaeb-e60d-2a16-696e-7b4d3d3548cb@redhat.com>
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From: Jesper Pedersen <jesper.pedersen@redhat.com>
Organization: Red Hat
Message-ID: <c448acf6-7c38-3d6d-c663-5387ccffb906@redhat.com>
Date: Fri, 25 Jan 2019 08:30:57 -0500
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Hi Kirk,

On 1/24/19 9:31 PM, Jamison, Kirk wrote:
> According to CF app, this patch needs review so I took a look at it.
> Currently, your patch applies and builds cleanly, and all tests are also successful
> based from the CF bot patch tester.
> 
> I'm not sure if I have understood the argument raised by Peter correctly.
> Quoting Peter, "it's not clear that pg_upgrade and vacuumdb are bound the same way, so it's not a given that the same -j number should be used."
> I think it's whether the # jobs for pg_upgrade is used the same way for parallel vacuum.
> 
> According to the official docs, the recommended setting for pg_upgrade --j option is the maximum of the number of CPU cores and tablespaces. [1]
> As for vacuumdb, parallel vacuum's (-j) recommended setting is based from your max_connections [2], which is the max # of concurrent connections to your db server.
>

Thanks for your feedback !

As per Peter's comments I have changed the patch (v2) to not pass down 
the -j option to vacuumdb.

Only an update to the documentation and console output is made in order 
to make it more clear.

Best regards,
  Jesper