From: Amit Kapila <amit.kapila@huawei.com>
To: "'Pavan Deolasee'" <pavan.deolasee@gmail.com>, "'Bruce Momjian'"
	<bruce@momjian.us>
CC: "'Josh Berkus'" <josh@agliodbs.com>, <pgsql-hackers@postgresql.org>
References: <20130109230731.GA30885@momjian.us>
 <50EE0D8C.3080602@agliodbs.com>
	<50ee5d46.06dd0e0a.440f.2a45SMTPIN_ADDED_BROKEN@mx.google.com>
	<CABOikdME0UyH9ATKN9y9dcWBMwo7DZdhD-_nTe5eCK1Kyt=vBw@mail.gmail.com>
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 <CABOikdME0UyH9ATKN9y9dcWBMwo7DZdhD-_nTe5eCK1Kyt=vBw@mail.gmail.com>
Subject: Re: 9.2.1 & index-only scans : abnormal heap fetches after VACUUM
 FULL
Date: Thu, 10 Jan 2013 14:48:05 +0530
Message-ID: <006a01cdef13$66aaa950$33fffbf0$@kapila@huawei.com>
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On Thursday, January 10, 2013 12:01 PM Pavan Deolasee wrote:
> On Thu, Jan 10, 2013 at 11:45 AM, Amit Kapila <amit.kapila@huawei.com>
> wrote:
> > On Thursday, January 10, 2013 6:09 AM Josh Berkus wrote:
> 
> >>
> >> 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.
> >
> 
> We can definitely do better than what we are doing today and that
> should fix many use cases and rebuild the VM for large part of the
> table if not all. More precisely, in cluster.c we can see what does
> HeapTupleSatisfiesVacuum() returns for every tuple in a page. If there
> are only DEAD or LIVE tuples in a page, we can set the VM bit. We may
> need similar additional checks for LIVE tuples like we have in vacuum
> code path. But its certainly doable.

>> Do we document this behavior or add a TODO item?
 

> Both?

IMO, we should do both.

With Regards,
Amit Kapila.


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