From: | Tomas Tamosaitis <tomas(dot)tamosaitis(at)connecty(dot)lt> |
---|---|
To: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: partitioned table and ORDER BY indexed_field DESC LIMIT 1 |
Date: | 2007-08-27 12:57:29 |
Message-ID: | 1188219449.8210.4.camel@localhost.localdomain |
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Lists: | pgsql-hackers pgsql-performance |
Pn, 2007 08 24 14:53 +0600, Anton rašė:
> Hi.
>
> I just created partitioned table, n_traf, sliced by month
> (n_traf_y2007m01, n_traf_y2007m02... and so on, see below). They are
> indexed by 'date_time' column.
> Then I populate it (last value have date 2007-08-...) and do VACUUM
> ANALYZE ON n_traf_y2007... all of it.
>
> Now I try to select latest value (ORDER BY date_time LIMIT 1), but
> Postgres produced the ugly plan:
>
> =# explain SELECT * FROM n_traf ORDER BY date_time DESC LIMIT 1;
> QUERY PL
can you test performance and send explain results of select like this :
select * from n_traf where date_time = (select max(date_time) from
n_traf);
i have similar problem with ~70M rows table (then using ordering), but
my table not partitioned.
I`m interesting how this select will works on partitioned table.
--
Pagarbiai,
Tomas Tamošaitis
Projektų Vadovas
Connecty
Skype://mazgis1009?add
Mob: +370 652 86127
e-pastas: tomas(dot)tamosaitis(at)connecty(dot)lt
web: www.connecty.lt
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