Re: Multi-Versions and Vacuum

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: grant <grant(at)amadensor(dot)com>
Cc: Anthony Berglas <anthony(dot)berglas(at)lucida(dot)com>, pgsql-general(at)postgresql(dot)org
Subject: Re: Multi-Versions and Vacuum
Date: 2002-07-19 16:03:49
Message-ID: 200207191603.g6JG3nQ13908@candle.pha.pa.us
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grant wrote:
> If Oracle uses multiple version concurrency, then why does it appear to do
> row locking (I use Oracle at work, but I do not admin it)
>
> The only downside I have seen to MVCS is the extra disk space, but with
> the performance improvements in a highly concurrent use environment, it is
> well worth it.
>
> Q: Does VACUUM FULL remove the rows that are too many for the FSM? Or,
> are they just stuck? I know that regular VACUUM will not allow reuse of
> overflowed rows. Also, how does one calculate the propper size for the
> FSM?

VACUUM full removes all unused rows from disk _including_ ones that
aren't in the free space map.

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