From: tv@fuzzy.cz
To: Martin Chlupac <martin.chlupac@rcware.eu>
Cc: pgsql-performance@postgresql.org
Subject: Re: Low disk performance?
Date: Thu, 18 Nov 2010 14:33:25 +0100
Message-ID: <a52ebff5c34aa3ae398abf0f92ec11fe.squirrel@sq.gransy.com> (raw)
In-Reply-To: <AANLkTimWyfi022t9mFO+3ZhPfR0AJAhLKdam4QDexcf6@mail.gmail.com>
References: <AANLkTimWyfi022t9mFO+3ZhPfR0AJAhLKdam4QDexcf6@mail.gmail.com>
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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To: pgsql-performance@postgresql.org
Cc: tv@fuzzy.cz, martin.chlupac@rcware.eu
Subject: Re: Low disk performance?
In-Reply-To: <a52ebff5c34aa3ae398abf0f92ec11fe.squirrel@sq.gransy.com>
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