To: robins@pobox.com
cc: pgsql-performance@postgresql.org
Subject: Re: Performance across multiple schemas 
In-reply-to: <36af4bed0708280605j5448ac52of6f7dc08791f0ab2@mail.gmail.com> 
References: <36af4bed0708280605j5448ac52of6f7dc08791f0ab2@mail.gmail.com>
Comments: In-reply-to Robins <tharakan@gmail.com>
	message dated "Tue, 28 Aug 2007 18:35:24 +0530"
Date: Tue, 28 Aug 2007 09:49:26 -0400
Message-ID: <23414.1188308966@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Robins <tharakan@gmail.com> writes:
> Could someone confirm as to whether a query across multiple schemas is known
> to have any kind of a degraded performance ?

Schemas are utterly, utterly irrelevant to performance.

I'm guessing you missed analyzing one of the tables, or forgot an index,
or something like that.  Also, if you did anything "cute" like use the
same table name in more than one schema, you need to check the
possibility that some query is selecting the wrong one of the tables.

The explain output you showed is no help because the expense is
evidently down inside one of the functions in the SELECT output list.

One thing you should probably try before getting too frantic is
re-ANALYZEing all the tables and then starting a fresh session to
clear any cached plans inside the functions.  If it's still slow
then it'd be worth digging deeper.

			regards, tom lane