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Message-ID: <2e78013d0701230543k54087265tce71bf74155dc8b1@mail.gmail.com>
Date: Tue, 23 Jan 2007 19:13:39 +0530
From: "Pavan Deolasee" <pavan.deolasee@gmail.com>
To: "Heikki Linnakangas" <heikki@enterprisedb.com>
Subject: Re: Free space management within heap page
Cc: "ITAGAKI Takahiro" <itagaki.takahiro@oss.ntt.co.jp>,
	"Martijn van Oosterhout" <kleptog@svana.org>, pgsql-hackers@postgresql.org
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On 1/23/07, Heikki Linnakangas <heikki@enterprisedb.com> wrote:
>
> 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
>
>
I guess ITAGAKI meant sizeof(ItemIdData) which is 4 bytes. Thats the data
type
for the line pointer.

Thanks,
Pavan

EnterpriseDB     http://www.enterprisedb.com

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<br><div><span class="gmail_quote">On 1/23/07, <b class="gmail_sendername">Heikki Linnakangas</b> &lt;<a href="mailto:heikki@enterprisedb.com">heikki@enterprisedb.com</a>&gt; wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
ITAGAKI Takahiro wrote:<br>&gt; BLCKSZ is typically 8192 bytes and sizeof(ItemPointerData) is 4 bytes.<br>&gt; 1/4 comes from 8192 / 4 = 2048. If we allow zero-size tuples, the line<br>&gt; pointers area can bloat up to the ratio. We have tuples no less than
<br>&gt; 32 bytes-size, so the area is restricted 256 bytes now.<br><br>sizeof(ItemPointerData) == 6 bytes<br><br></blockquote></div><br>I guess ITAGAKI meant sizeof(ItemIdData) which is 4 bytes. Thats the data type<br>for the line pointer.
<br><br>Thanks,<br>Pavan<br><br>EnterpriseDB&nbsp;&nbsp;&nbsp;&nbsp; <a href="http://www.enterprisedb.com">http://www.enterprisedb.com</a>

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