From: Heikki Linnakangas <heikki@enterprisedb.com>
To: ITAGAKI Takahiro <itagaki.takahiro@oss.ntt.co.jp>
Cc: Pavan Deolasee <pavan.deolasee@gmail.com>
Cc: Martijn van Oosterhout <kleptog@svana.org>
Cc: pgsql-hackers@postgresql.org
Subject: Re: Free space management within heap page
Date: Tue, 23 Jan 2007 13:18:55 +0000
Message-ID: <45B60B3F.2030707@enterprisedb.com> (raw)
In-Reply-To: <20070123191419.55E4.ITAGAKI.TAKAHIRO@oss.ntt.co.jp>
References: <20070123181802.55E1.ITAGAKI.TAKAHIRO@oss.ntt.co.jp>
<45B5DEBF.3090200@enterprisedb.com>
<20070123191419.55E4.ITAGAKI.TAKAHIRO@oss.ntt.co.jp>
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
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To: pgsql-hackers@postgresql.org
Cc: heikki@enterprisedb.com, itagaki.takahiro@oss.ntt.co.jp, pavan.deolasee@gmail.com, kleptog@svana.org
Subject: Re: Free space management within heap page
In-Reply-To: <45B60B3F.2030707@enterprisedb.com>
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