Received: from localhost (maia-2.hub.org [200.46.204.187]) by postgresql.org (Postfix) with ESMTP id 6364F9FB28B for ; Tue, 23 Jan 2007 09:19:25 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.187]) (amavisd-new, port 10024) with ESMTP id 25306-06 for ; Tue, 23 Jan 2007 09:19:16 -0400 (AST) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.4 Received: from wr-out-0506.google.com (wr-out-0506.google.com [64.233.184.237]) by postgresql.org (Postfix) with ESMTP id 6AD979FB223 for ; Tue, 23 Jan 2007 09:19:21 -0400 (AST) Received: by wr-out-0506.google.com with SMTP id 68so1013212wra for ; Tue, 23 Jan 2007 05:19:20 -0800 (PST) DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:user-agent:mime-version:to:cc:subject:references:in-reply-to:content-type:content-transfer-encoding:sender; b=AXO5/9SIcjRH6uqyv5Dx5aBVFcWUTEC4//3kbpkJeJhny1dXKpbPTG9vt3uQZfJeQ2ylJGbq2yTMFfh5+si9PQkOxX+LL1XLCYD29SU21kLYfb2Ur7UwwQo4X3VHxL5XOjoJ3rvTfKlwqzlqrUPIzeEVe8VMaBXlPOxL5bO10Oo= Received: by 10.78.205.7 with SMTP id c7mr334052hug.1169558353185; Tue, 23 Jan 2007 05:19:13 -0800 (PST) Received: from ?172.24.32.32? ( [62.232.55.118]) by mx.google.com with ESMTP id 37sm8004773hub.2007.01.23.05.19.11; Tue, 23 Jan 2007 05:19:11 -0800 (PST) Message-ID: <45B60B3F.2030707@enterprisedb.com> Date: Tue, 23 Jan 2007 13:18:55 +0000 From: Heikki Linnakangas User-Agent: Icedove 1.5.0.8 (X11/20061116) MIME-Version: 1.0 To: ITAGAKI Takahiro CC: Pavan Deolasee , Martijn van Oosterhout , pgsql-hackers@postgresql.org Subject: Re: Free space management within heap page References: <20070123181802.55E1.ITAGAKI.TAKAHIRO@oss.ntt.co.jp> <45B5DEBF.3090200@enterprisedb.com> <20070123191419.55E4.ITAGAKI.TAKAHIRO@oss.ntt.co.jp> In-Reply-To: <20070123191419.55E4.ITAGAKI.TAKAHIRO@oss.ntt.co.jp> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200701/1052 X-Sequence-Number: 96953 ITAGAKI Takahiro wrote: > BLCKSZ is typically 8192 bytes and sizeof(ItemPointerData) is 4 bytes. > 1/4 comes from 8192 / 4 = 2048. If we allow zero-size tuples, the line > pointers area can bloat up to the ratio. We have tuples no less than > 32 bytes-size, so the area is restricted 256 bytes now. sizeof(ItemPointerData) == 6 bytes > We can recycle unused line pointers, but we cannot shrink the area unless > the tail end of line pointers are removed. i.e, unusable free space will > remains at the middle of LP area. Yeah, agreed. It'd still be a good idea to do it when possible. -- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com