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Re: 9.2.1 & index-only scans : abnormal heap fetches after VACUUM FULL

From: Amit Kapila <amit(dot)kapila(at)huawei(dot)com>
To: "'Josh Berkus'" <josh(at)agliodbs(dot)com>, <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: 9.2.1 & index-only scans : abnormal heap fetches after VACUUM FULL
Date: 2013-01-10 06:15:47
Message-ID: 006901cdeef9$eefd56a0$ccf803e0$@kapila@huawei.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Thursday, January 10, 2013 6:09 AM Josh Berkus wrote:
> On 01/09/2013 03:07 PM, Bruce Momjian wrote:
> > How do we want to handle the case where VACUUM FULL clears the
> > visibility map, causing loss of index-only scans?
> >
> > 	http://archives.postgresql.org/pgsql-performance/2012-
> 11/msg00317.php
> >
> > Do we document this behavior or add a TODO item?
> >
> 
> Both?
> 
> Surely VACUUM FULL should rebuild the visibility map, and make tuples
> in
> the new relation all-visible, no?

I think it cannot made all visible.
How about if any transaction in SSI mode is started before Vacuum Full, should it see all tuples.

With Regards,
Amit Kapila.



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