Re: Reduce the size of PageFreeSpaceInfo on 64bit platform

From: Decibel! <decibel(at)decibel(dot)org>
To: ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>
Cc: pgsql-patches(at)postgresql(dot)org
Subject: Re: Reduce the size of PageFreeSpaceInfo on 64bit platform
Date: 2007-08-10 19:47:55
Message-ID: 20070810194755.GE20424@nasby.net
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On Fri, Aug 10, 2007 at 10:32:35AM +0900, ITAGAKI Takahiro wrote:
> Here is a patch to reduce the size of PageFreeSpaceInfo on 64bit platform.
> We will utilize maintenance_work_mem twice with the patch.
>
> The sizeof(PageFreeSpaceInfo) is 16 bytes there because the type of 'avail'
> is 'Size', that is typically 8 bytes and needs to be aligned in 8-byte bounds.
> I changed the type of the field to uint32. We can store the freespace with
> uint16 at smallest, but the alignment issue throws it away.

So... does that mean that the comment in the config file about 6 bytes
per page is incorrect?
--
Decibel!, aka Jim Nasby decibel(at)decibel(dot)org
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)

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