From: Andrew Sullivan <ajs@crankycanuck.ca>
To: pgsql-sql@postgresql.org
Subject: Re: row-attribute in EXPLAIN-output doesn't match count(*)
Date: Thu, 14 Apr 2005 13:10:12 -0400
Message-ID: <20050414171012.GA9027@phlogiston.dyndns.org> (raw)
In-Reply-To: <200504141838.14705.andreak@officenet.no>
References: <200504141838.14705.andreak@officenet.no>
On Thu, Apr 14, 2005 at 06:38:14PM +0200, Andreas Joseph Krogh wrote:
> Hi everybody, I have table which inly has 298 rows in it, but EXPLAIN ANALYZE
> shows that PG thinks it has as much as 160057 rows AFAICT from the
> EXPLAIN-output.
It does have 160057 rows:
> INFO: vacuuming "public.onp_web_index"
> INFO: "onp_web_index": found 0 removable, 160057 nonremovable row versions in
> 206940 pages
> DETAIL: 159759 dead row versions cannot be removed yet.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
You no doubt have a long-running transaction keeping the rows from
being recovered. Look for "idle in transaction" as a first guess.
> DETAIL: 160057 index row versions were removed.
> 0 index pages have been deleted, 0 are currently reusable.
> CPU 2.40s/0.92u sec elapsed 286.41 sec.
>
> Here it says that it removed 160057 rows, doesn't it?
No; that's the index row versions.
> Is this normal, shall I just overlook the "rows=160057" output from EXPLAIN,
> or is something wrong?
> What does the line "DETAIL: 159759 dead row versions cannot be removed yet."
> mean?
It means that those rows were marked invalidated after some existing
transaction started.
A
--
Andrew Sullivan | ajs@crankycanuck.ca
The plural of anecdote is not data.
--Roger Brinner
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To: pgsql-sql@postgresql.org
Cc: ajs@crankycanuck.ca
Subject: Re: row-attribute in EXPLAIN-output doesn't match count(*)
In-Reply-To: <20050414171012.GA9027@phlogiston.dyndns.org>
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