Date: Sat, 20 Jul 2019 11:21:52 -0700
From: Noah Misch <noah@leadboat.com>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@postgresql.org
Subject: Re: [RFC] Removing "magic" oids
Message-ID: <20190720182152.GB1865623@rfd.leadboat.com>
References: <20180930034810.ywp2c7awz7opzcfr@alap3.anarazel.de>
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 <20181120092004.f3j2znfodallkksn@alap3.anarazel.de>
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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.