am Fri, dem 05.12.2008, um 11:41:11 +0100 mailte Rogatzki Rainer folgendes:
> -- Example with bad performance since index isn't used
> explain
> select c.id_country, sum(c.cost) as sum_cost
> from costs c, accounting_interval a
> where c.id_user = 123
> and c.id_state = 1
> and a.id = 1
> and date(c.request) between a.p_begin and a.p_until
> group by id_country;
>
> -- Example with invoked index (100 times better performance)
> explain
> select c.id_country, sum(c.cost) as sum_cost
> from costs c
> where c.id_user = 123
> and c.id_state = 1
> and date(c.request) between '2007-01-01'::date and '2007-01-31'::date
> group by id_country;
>
> Here I cannot see why statement preparation has an effect at all.
The planner don't know the parameters at compile-time. Because of this
fakt, the planner choose a other plan (a seq-scan).
You can try to use execute 'your query'. In this case the planner
investigate a new plan, and (maybe) with the index.
Andreas
--
Andreas Kretschmer
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