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Re: Low disk performance?

From: tv(at)fuzzy(dot)cz
To: "Martin Chlupac" <martin(dot)chlupac(at)rcware(dot)eu>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Low disk performance?
Date: 2010-11-18 13:33:25
Message-ID: a52ebff5c34aa3ae398abf0f92ec11fe.squirrel@sq.gransy.com (view raw or flat)
Thread:
Lists: pgsql-performance
Hi, what is the size of the table and index (in terms of pages and
tuples)? Try something like

SELECT relpages, reltuples FROM pg_class WHERE relname = 'table or index
name';

And what indexes have you created? It seems to me there's just index on
the variable_id. It might be useful to create index on (variable_id, ts)
or even (variable_id, ts, good_through).

Tomas

> Hello everybody,
> having this SQL query:
>
> --------------
> select
> variable_id,float_value,ts,good_through,interval,datetime_value,string_value,int_value,blob_value,history_value_type
> from "records_437954e9-e048-43de-bde3-057658966a9f" where variable_id
> in (22727) and (ts >= '2010-10-02 11:19:55' or good_through >=
> '2010-10-02 11:19:55') and (ts <= '2010-10-14 11:19:55' or
> good_through <= '2010-10-14 11:19:55')
> union all
> select
> variable_id,float_value,ts,good_through,interval,datetime_value,string_value,int_value,blob_value,history_value_type
> from "records_1d115712-e943-4ae3-bb14-b56a95796111" where variable_id
> in (24052) and (ts >= '2010-10-02 11:19:55' or good_through >=
> '2010-10-02 11:19:55') and (ts <= '2010-10-14 11:19:55' or
> good_through <= '2010-10-14 11:19:55')
> order by ts
> limit 2501 offset 0
>
> ---------------
>
> and these two results:
>
> 1st run:
> http://explain.depesz.com/s/1lT
>
> 2nd run:
> http://explain.depesz.com/s/bhA
>
> is there anything I can do about the speed? Only buying faster
> hard-disk seems to me as the solution... Am I right?
>
> Thank you in advance
>   Martin
>
> --
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Subject: Re: Query Performance SQL Server vs. Postgresql
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Subject: Low disk performance?

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