Re: Strange query plan - Mailing list pgsql-performance

From Robert Haas
Subject Re: Strange query plan
Date
Msg-id CA+TgmobFAopH3OHgGWoEFRXXErVU3FLSJ5Rm0zfQkOO2O7baGg@mail.gmail.com
Whole thread Raw
In response to Re: Strange query plan  ("Sorbara, Giorgio (CIOK)" <Giorgio.Sorbara@fao.org>)
Responses Re: Strange query plan
List pgsql-performance
On Mon, Oct 31, 2011 at 9:52 AM, Sorbara, Giorgio (CIOK)
<Giorgio.Sorbara@fao.org> wrote:
> Group  (cost=0.00..4674965.80 rows=200 width=17) (actual time=13.375..550943.592 rows=1 loops=1)
>   ->  Append  (cost=0.00..4360975.94 rows=125595945 width=17) (actual time=13.373..524324.817 rows=125595932 loops=1)
>         ->  Index Scan using f_suipy_pkey on f_suipy  (cost=0.00..5.64 rows=1 width=58) (actual time=0.019..0.019
rows=0loops=1) 
>               Index Cond: ((fk_theme)::text = 'main_py_six_scxc'::text)
>         ->  Seq Scan on f_suipy_main_py_six_scxc f_suipy  (cost=0.00..4360970.30 rows=125595944 width=17) (actual
time=13.352..495259.117rows=125595932 loops=1) 
>               Filter: ((fk_theme)::text = 'main_py_six_scxc'::text)
>  Total runtime: 550943.699 ms

How fast do you expect this to run?  It's aggregating 125 million
rows, so that's going to take some time no matter how you slice it.
Unless I'm misreading this, it's actually taking only about 4
microseconds per row, which does not obviously suck.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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