Message-ID: <47623103.7030700@pws.com.au>
Date: Fri, 14 Dec 2007 18:30:11 +1100
From: Russell Smith <mr-russ@pws.com.au>
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To: Simon Riggs <simon@2ndquadrant.com>
CC: Kevin Grittner <Kevin.Grittner@wicourts.gov>,
	pgsql-performance@postgresql.org
Subject: Re: Heavy write activity on first vacuum of fresh TOAST
 data
References: <4760FF69.EE98.0025.0@wicourts.gov>	
	<1197562283.4255.1829.camel@ebony.site>
	<47611B9D.EE98.0025.0@wicourts.gov>	
	<1197569564.4255.1855.camel@ebony.site>
	<47614D86.EE98.0025.0@wicourts.gov>
	<1197582010.4255.1912.camel@ebony.site>
In-Reply-To: <1197582010.4255.1912.camel@ebony.site>
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Simon Riggs wrote:
> On Thu, 2007-12-13 at 15:19 -0600, Kevin Grittner wrote:
>   
>> What impact would lack of the hint bits have until a vacuum?
>>     
>
> Vacuum isn't important here. Its the first idiot to read the data that
> gets hit.
>
>   
Given vacuum must then touch every page, is there a win in only setting 
hint bits on pages where vacuum has to do some other work on the page?  
As vacuum is causing significant IO load for data that may not be 
accessed for some time.

The question becomes what is the impact of not setting hint bits?  Is it 
better or worse than the IO caused by vacuum?

Regards

Russell Smith