Date: Fri, 6 May 2016 13:19:32 -0300
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: =?utf-8?B?T25kxZllaiBTdsSbdGzDrWs=?= <osvetlik@flexibee.eu>,
	pgsql-admin@postgresql.org
Subject: Re: Autovacuum of pg_database
Message-ID: <20160506161932.GA216183@alvherre.pgsql>
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Tom Lane wrote:
> Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> > Tom Lane wrote:
> >> I think it's pretty obvious: autovacuum.c's rule for detecting whether
> >> some other worker is already processing table X is wrong when X is a
> >> shared table.  I propose the attached patch.
> 
> > Hmm, I have pretty much the same patch, except I added the flag to
> > struct autovac_table and have it populated by table_recheck_autovac.
> > Haven't tested this yet, which is why I hadn't posted it.
> 
> Actually, I realized after looking at it that the new wi_tableshared
> field is unnecessary in my patch.  The only important part is that
> knowledge of relisshared be available when we're looking for conflicting
> workers, and that is entirely local in do_autovacuum().  I'd started the
> patch by adding wi_tableshared, on the expectation that it would be
> necessary, but it ain't ...

OK, if I understand you correctly then that is what my patch does -- the
"sharedrel" flag in my patch is only inside do_autovacuum.  Do you
already have a test rig for this?  If not, I can set one up so that I
can push the patch hopefully later today.

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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