Received: from magus.postgresql.org (magus.postgresql.org [87.238.57.229])
	by mail.postgresql.org (Postfix) with ESMTP id 38DE7A01097
	for <pgsql-hackers@postgresql.org>;
	Wed, 30 Nov 2011 14:45:34 -0400 (AST)
Received: from sss.pgh.pa.us ([66.207.139.130])
	by magus.postgresql.org with esmtp (Exim 4.72)
	(envelope-from <tgl@sss.pgh.pa.us>) id 1RVp9w-0006MH-I7
	for pgsql-hackers@postgresql.org; Wed, 30 Nov 2011 18:45:33 +0000
Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1])
	by sss.pgh.pa.us (8.14.2/8.14.2) with ESMTP id pAUIjF8E025166;
	Wed, 30 Nov 2011 13:45:16 -0500 (EST)
To: Robert Haas <robertmhaas@gmail.com>
cc: Florian Weimer <fweimer@bfk.de>, pgsql-hackers@postgresql.org
Subject: Re: Large number of open(2) calls with bulk INSERT into empty table 
In-reply-to: 
 <CA+Tgmoac+6qTNp2U+wedY8-PU6kK_b6hbdhR5xYGBG3GtdFcww@mail.gmail.com>
References: <82ipm51tcd.fsf@mid.bfk.de>
	<CA+TgmoYRGO5Wu4_2yzP0-cmx4GBZHqOO4WKiCxT-R3gV6qrt6A@mail.gmail.com>
	<23238.1322674187@sss.pgh.pa.us>
	<CA+Tgmoac+6qTNp2U+wedY8-PU6kK_b6hbdhR5xYGBG3GtdFcww@mail.gmail.com>
Comments: In-reply-to Robert Haas <robertmhaas@gmail.com>
	message dated "Wed, 30 Nov 2011 13:30:58 -0500"
Date: Wed, 30 Nov 2011 13:45:15 -0500
Message-ID: <25165.1322678715@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
X-Pg-Spam-Score: -3.1 (---)
X-Archive-Number: 201111/1752
X-Sequence-Number: 199236

Robert Haas <robertmhaas@gmail.com> writes:
> Yikes!  A table with 4 bytes of useful data is consuming 40kB on disk
> - 8kB in the main form, 8kB in the VM fork, and 24kB in the FSM fork.
> Ouch!

Yeah, ouch.  Why is the FSM fork eating so much space --- I'd have
expected 8k there, but 24?

Also, if VACUUM is going to cause the FSM to be created anyway, there
may not be a lot of point to refraining from creating the first page
right away.

			regards, tom lane