Re: Dead Space Map

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Hannu Krosing <hannu(at)skype(dot)net>
Cc: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Dead Space Map
Date: 2006-02-28 15:26:31
Message-ID: 15088.1141140391@sss.pgh.pa.us
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Hannu Krosing <hannu(at)skype(dot)net> writes:
> There is no fundamental reason, why vacuum needs to run in a transaction
> itselt.

I'll just take one point: you cannot hold locks unless you have a
transaction, therefore you cannot even look up the catalog info about
the table you wish to vacuum; let alone prevent someone else from
dropping the table under you.

The current bgwriter is incapable of looking at catalog contents as
such --- it operates only at the level of physical data blocks.

regards, tom lane

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