To: Josh Berkus <josh@agliodbs.com>
cc: pgsql-performance@postgresql.org
Subject: Re: Issue for partitioning with extra check constriants 
In-reply-to: <4CAA1E1B.8080505@agliodbs.com> 
References: <4CA672D7.3070405@agliodbs.com> <1548.1285977377@sss.pgh.pa.us>
	<4CA67580.7070003@agliodbs.com> <6813.1285978581@sss.pgh.pa.us>
	<4CAA1E1B.8080505@agliodbs.com>
Comments: In-reply-to Josh Berkus <josh@agliodbs.com>
	message dated "Mon, 04 Oct 2010 11:34:03 -0700"
Date: Mon, 04 Oct 2010 19:36:40 -0400
Message-ID: <9984.1286235400@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Josh Berkus <josh@agliodbs.com> writes:
>> And your point is?  The design center for the current setup is maybe 5
>> or 10 partitions.  We didn't intend it to be used for more partitions
>> than you might have spindles to spread the data across.

> Where did that come from?  It certainly wasn't anywhere when the feature
> was introduced.  Simon intended for this version of partitioning to
> scale to 100-200 partitions (and it does, provided that you dump all
> other table constraints), and partitioning has nothing to do with
> spindles.  I think you're getting it mixed up with tablespaces.

[ shrug... ]  If Simon thought that, he obviously hadn't done any
careful study of the planner's performance.  You can maybe get that far
as long as the partitions have just very simple constraints, but
anything nontrivial won't scale.  As you found out.

			regards, tom lane