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List:       pgsql-performance
Subject:    Re: [PERFORM] Curious about dead rows.
From:       Mario Weilguni <mweilguni () sime ! com>
Date:       2007-11-14 19:21:24
Message-ID: 473B4AB4.70506 () sime ! com
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Jean-David Beyer schrieb:
> I am doing lots of INSERTs on a table that starts out empty (I did a
> TRUNCATE on it). I am not, AFAIK, doing DELETEs or UPDATEs. Autovacuum is
> on. I moved logging up to debug2 level to see what was going on, and I get
> things like this:
>
>  "vl_as": scanned 3000 of 5296 pages, containing 232944 live rows and 1033
> dead rows; 3000 rows in sample, 411224 estimated total rows
>
> A little later, it says:
>
> "vl_as": scanned 3000 of 6916 pages, containing 233507 live rows and 493
> dead rows; 3000 rows in sample, 538311 estimated total rows
>
> (I suppose that means autovacuum is working.) Is this normal, or have I got
> something wrong? Why so many dead rows when just doing inserts? It is not
> that I think the number is too high, considering the number of rows in the
> table at the point where I copied this line. It is just that I do not
> understand why there are any.
>
>   
Did you rollback some transactions? It will generate dead rows too - at 
least I think so.

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