Re: Multi-Versions and Vacuum

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От Bruce Momjian
Тема Re: Multi-Versions and Vacuum
Дата
Msg-id 200207191603.g6JG3nQ13908@candle.pha.pa.us
обсуждение исходный текст
Ответ на Re: Multi-Versions and Vacuum  (grant <grant@amadensor.com>)
Ответы Re: Multi-Versions and Vacuum  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-general
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.

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
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