Re: optimizer ignoring primary key and doing sequence scan

On Mon, Jul 14, 2008 at 1:54 PM, Chris Hoy <chris.hoy@hoyc.fsnet.co.uk> wrote:
>
> Hi
>
> I have a number of tables in my database where the queries appear to
> ignoring the primary key and doing a seq scan instead, however other tables
> appear to be fine. I can see any difference between them.
>
> Is their any way of determination why the otimizer isn't picking up the
> primary key?
>
> Version 8.3.3 windows
>
> An example of a non working table is:
>
> select * from industries where industryid = 1;
> "Seq Scan on industries  (cost=0.00..1.02 rows=1 width=116) (actual
> time=0.011..0.013 rows=1 loops=1)"

According to this there's only one row in the table.  why WOULD
postgresql use an index when it can just scan the one row table in a
split second.