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Re: Dead Space Map version 3 (simplified)

From: Hiroki Kataoka <kataoka(at)interwiz(dot)jp>
To: Gregory Stark <stark(at)enterprisedb(dot)com>
Cc: pgsql-patches(at)postgresql(dot)org
Subject: Re: Dead Space Map version 3 (simplified)
Date: 2007-04-24 07:22:39
Message-ID: 462DB03F.2030803@interwiz.jp (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
Gregory Stark wrote:
> "Hiroki Kataoka" <kataoka(at)interwiz(dot)jp> writes:
> 
>> I think there is no problem.  Bloating will make pages including the
>> unnecessary area which will not be accessed.  Soon, those pages will be
>> registered into DSM.
> 
> Except the whole point of the DSM is to let us vacuum those pages *before*
> that happens...

You are right.  However, expecting perfection will often lose 
performance.  Delaying processing to some extent leads to performance.

Even if hot page is not vacuumed, it does not mean generating dead 
tuples boundlessly.  About one hot page, the quantity of dead tuple 
which continues existing unnecessarily is at most 1 page or its extent. 
  Also that page is soon registered into DSM by checkpoint like fail-safe.

Isn't some compromise need as first version of DSM vacuum?

-- 
Hiroki Kataoka <kataoka(at)interwiz(dot)jp>

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