Date: Sat, 20 Jul 2019 12:56:34 -0700
From: Andres Freund <andres@anarazel.de>
To: Noah Misch <noah@leadboat.com>
Cc: pgsql-hackers@postgresql.org
Subject: Re: [RFC] Removing "magic" oids
Message-ID: <20190720195634.qgomnrssru7iw74y@alap3.anarazel.de>
References: <20180930034810.ywp2c7awz7opzcfr@alap3.anarazel.de>
 <20181114080152.xkk6coduvfrh4ntr@alap3.anarazel.de>
 <20181115045728.GA1121738@rfd.leadboat.com>
 <20181115050241.exereob7wk3xxewj@alap3.anarazel.de>
 <20181120092004.f3j2znfodallkksn@alap3.anarazel.de>
 <20190707170035.GA1485546@rfd.leadboat.com>
 <20190719171257.urgz76ob753ygxmd@alap3.anarazel.de>
 <20190720182152.GB1865623@rfd.leadboat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20190720182152.GB1865623@rfd.leadboat.com>
Precedence: bulk

Hi,

On 2019-07-20 11:21:52 -0700, Noah Misch wrote:
> On Fri, Jul 19, 2019 at 10:12:57AM -0700, Andres Freund wrote:
> > On 2019-07-07 10:00:35 -0700, Noah Misch wrote:
> > > +# Test concurrent OID generation via pg_enum_oid_index.  This indirectly
> > > +# exercises LWLock and spinlock concurrency.
> > > +my $labels = join ',', map { "'l$_'" } 1 .. 1000;
> > >  pgbench(
> > >  	'--no-vacuum --client=5 --protocol=prepared --transactions=25',
> > >  	0,
> > >  	[qr{processed: 125/125}],
> > >  	[qr{^$}],
> > > -	'concurrent insert workload',
> > > +	'concurrent OID generation',
> > >  	{
> > >  		'001_pgbench_concurrent_insert' =>
> > > -		  'INSERT INTO insert_tbl SELECT FROM generate_series(1,1000);'
> > > +		  "CREATE TYPE pg_temp.e AS ENUM ($labels); DROP TYPE pg_temp.e;"
> > >  	});
> > 
> > Hm, perhaps we should just do something stupid an insert into a catalog
> > table, determining the oid to insert with pg_nextoid?  That ought to be a
> > lot faster and thus more "stress testing" than going through a full
> > blown DDL statement?  But perhaps that's just too ugly.
> 
> I expect the pg_nextoid strategy could have sufficed.  The ENUM strategy
> wastes some time parsing 1000 label names, discarding odd-numbered OIDs, and
> dropping the type.  The pg_nextoid strategy wastes time by performing the
> insertion loop in the executor instead of dedicated C code of
> EnumValuesCreate().  Hard to say how to weight those factors.

Fair enough. Are you planning to commit your changes?

Greetings,

Andres Freund