Re: Seq Scan

From: Dan Harris <fbsd(at)drivefaster(dot)net>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: Seq Scan
Date: 2007-06-01 16:59:01
Message-ID: 46605055.3070305@drivefaster.net
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Tyler Durden wrote:
> Hi,
> I'm having some problems in performance in a simple select count(id)
> from.... I have 700 000 records in one table, and when I do:
>
> # explain select (id) from table_name;
> -[ RECORD 1
> ]----------------------------------------------------------------
> QUERY PLAN | Seq Scan on table_name (cost=0.00..8601.30 rows=266730
> width=4)
>
> I had created an index for id(btree), but still shows "Seq Scan".
> What I'm doing wrong?
>
> Thanks,
> Tyler
>
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Have you searched our list archives?
>
> http://archives.postgresql.org

select count(*) will *always* do a sequential scan, due to the MVCC
architecture. See archives for much discussion about this.

-Dan

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