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Re: Dead Space Map patch

From: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
To: "ITAGAKI Takahiro" <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>
Cc: <pgsql-patches(at)postgresql(dot)org>
Subject: Re: Dead Space Map patch
Date: 2006-12-28 19:40:30
Message-ID: 1167334830.3633.177.camel@silverbirch.site (view raw or flat)
Thread:
Lists: pgsql-patches
On Thu, 2006-12-28 at 15:14 +0900, ITAGAKI Takahiro wrote:
> Even if it is off, DSM are always recorded and updated.

The purpose of the patch, as I understand it, is performance. 

Can I ask what the performance overhead of this is for standard OLTP
workloads?

Do you have some performance numbers for VACUUM with/without this patch?
Presumably it does speed things up considerably, but question is, how
much?

Is there a point where you VACUUM more than x% of a table that it is
actually better to just VACUUM the whole thing, because of readahead?

Is there a size of table for which keeps dsm information is not
worthwhile? i.e. small tables

-- 
  Simon Riggs             
  EnterpriseDB   http://www.enterprisedb.com



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