Date: Wed, 10 Jan 2007 14:07:54 -0600
From: "Jim C. Nasby" <jim@nasby.net>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Erik Jones <erik@myemma.com>, pgsql-performance@postgresql.org
Subject: Re: More 8.2 client issues (Was: [Slow dump?)
Message-ID: <20070110200753.GR12217@nasby.net>
References: <459AD5A8.7030102@myemma.com> <22512.1167779361@sss.pgh.pa.us>
	<459BD61C.3030202@myemma.com> <11617.1167841479@sss.pgh.pa.us>
	<459BDC98.8030008@myemma.com> <12515.1167843380@sss.pgh.pa.us>
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On Wed, Jan 03, 2007 at 11:56:20AM -0500, Tom Lane wrote:
> Erik Jones <erik@myemma.com> writes:
> > Tom Lane wrote:
> >> I could see this taking an unreasonable amount of time if you had a huge
> >> number of pg_class rows or a very long search_path --- is your database
> >> at all out of the ordinary in those ways?
> >> 
> > Well, running "select count(*) from pg_class;" returns 524699 rows
> 
> Ouch.
> 
> > our search path is the default.  I'd also like to reiterate that \d 
> > pg_class returns instantly when run from the 8.1.4 psql client connected 
> > to the 8.2 db.
> 
> I think I know where the problem is: would you compare timing of
> 
> 	select * from pg_class where c.relname ~ '^(pg_class)$';
> 
> 	select * from pg_class where c.relname ~ '^pg_class$';
> 
> Recent versions of psql put parentheses into the regex pattern for
> safety in case it's got "|", but I just realized that that probably
> confuses the optimizer's check for an indexable regex :-(
> 
> However, this only explains slowdown in psql's \d commands, which
> wasn't your original complaint ...

On the other hand, with 500k relations pg_dump is presumably going to be
doing a lot of querying of the catalog tables, so if it uses similar
queries...
-- 
Jim Nasby                                            jim@nasby.net
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)