From: Tom Lane <tgl@sss.pgh.pa.us>
To: Bruce Momjian <bruce@momjian.us>
Cc: Andrew Dunstan <andrew@dunslane.net>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [PERFORM] encouraging index-only scans
Date: Wed, 12 Dec 2012 22:51:38 -0500
Message-ID: <23298.1355370698@sss.pgh.pa.us> (raw)
In-Reply-To: <20121213024837.GB22363@momjian.us>
References: <50C8F1EC.9010801@dunslane.net>
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<50C90154.8060103@dunslane.net>
<50C904DB.9090305@dunslane.net>
<20121213024837.GB22363@momjian.us>
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Bruce Momjian <bruce@momjian.us> writes:
> On Wed, Dec 12, 2012 at 05:27:39PM -0500, Andrew Dunstan wrote:
>> Actually, the table had been analysed but not vacuumed, so this
>> kinda begs the question what will happen to this value on
>> pg_upgrade? Will people's queries suddenly get slower until
>> autovacuum kicks in on the table?
> [ moved to hackers list.]
> Yes, this does seem like a problem for upgrades from 9.2 to 9.3? We can
> have pg_dump --binary-upgrade set these, or have ANALYZE set it. I
> would prefer the later.
ANALYZE does not set that value, and is not going to start doing so,
because it doesn't scan enough of the table to derive a trustworthy
value.
It's been clear for some time that pg_upgrade ought to do something
about transferring the "statistics" columns in pg_class to the new
cluster. This is just another example of why.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, bruce@momjian.us, andrew@dunslane.net, pgsql-hackers@postgresql.org
Subject: Re: [PERFORM] encouraging index-only scans
In-Reply-To: <23298.1355370698@sss.pgh.pa.us>
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