From: | "Zeugswetter Andreas ADI SD" <ZeugswetterA(at)spardat(dot)at> |
---|---|
To: | "Simon Riggs" <simon(at)2ndquadrant(dot)com> |
Cc: | "Hannu Krosing" <hannu(at)skype(dot)net>, <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Revitalising VACUUM FULL for 8.3 |
Date: | 2007-03-01 14:03:39 |
Message-ID: | E1539E0ED7043848906A8FF995BDA57901CAFFE8@m0143.s-mxs.net |
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Lists: | pgsql-hackers |
> > > -- start the VACUUM from the first non-filled block
> > >
> > > So if we do this, we wouldn't need to worry about HOT tuples at
all,
> > > nor would we need to wait until all transactions are gone.
> >
> > You need to wait until you are allowed to truncate if you want
> > concurrency.
> > Or a concurrent scan might miss a row, because the visible tuple got
> > truncated away.
>
> I was not suggesting that we remove visible rows through truncation.
Sure, unless you suggest to not truncate during this vacuum run ?
But we are talking about vacuum full, so truncation is essential.
It was suggested to do a dummy null update to move live tuples up front.
The old version is still visible for serializable txns.
Andreas
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