Re: Surprising dead_tuple_count from pgstattuple

From: Gordon Shannon <gordo169(at)gmail(dot)com>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Surprising dead_tuple_count from pgstattuple
Date: 2010-08-07 04:43:11
Message-ID: 1281156191668-2267263.post@n5.nabble.com
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Robert Haas wrote:
>
> My thought would be "is autovacuum running in the background in
> between these commands?".
>

That's a good thought, but no, autovacuum_vacuum_scale_factor is set to 0.2,
meaning that over 1 million dead tuples are necessary for autovacuum.
Besides, if autovacuum had run, I think the pg_stat_user_tables.n_dead_tup
would have reset to zero, as it did after my manual vacuum.

Regarding HOT prune, I never did any updates, so I think there couldn't be
any HOT tuples. Or does HOT prune do more than that?
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