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From: Tomas Vondra <tv@fuzzy.cz>
To: Marti Raudsepp <marti@juffo.org>
Cc: sridhar bamandlapally <sridhar.bn1@gmail.com>
Cc: pgsql-performance <pgsql-performance@postgresql.org>
Subject: Re: PostgreSQL Parallel Processing !
Date: Fri, 27 Jan 2012 10:46:03 +0100
Message-ID: <31f8d7cae7e7e0044e368d1cec6e7077.squirrel@sq.gransy.com> (raw)
In-Reply-To: <CABRT9RD_VXa4zEDVYoe4a0TgDFbidBC884q_2S47hyre_Sp9Sg@mail.gmail.com>
References: <CAFAjSHxCuDP6cN1d1zOvFeDsFvM9HJkOSooFNTOWSKpuo-XRJw@mail.gmail.com>
	<CAGuFTBXYSyDHYBuvBOm5gaHtuwg6wEkSu3xB++5SxXiSpNwv=Q@mail.gmail.com>
	<CAGTBQpbm2uSfsQ=B-ASH36dKMknnoYmJFwe+OmSqjX6X_vvgUg@mail.gmail.com>
	<CAHyXU0zRRWrV5p1U6zAhz=95m3y4Z_9WdYBGwNuKEFX_t1ySnw@mail.gmail.com>
	<CAGTBQpaS1DeN8hpq=Rb4Q9JkR4JrCucwgaP1wW7T48K9tbWO0Q@mail.gmail.com>
	<CAGuFTBWibLVRrS-yQZCvuZ_62T=DOustwtK1VaQhcQMdn1axWw@mail.gmail.com>
	<CABRT9RD_VXa4zEDVYoe4a0TgDFbidBC884q_2S47hyre_Sp9Sg@mail.gmail.com>

On 27 Leden 2012, 10:06, Marti Raudsepp wrote:
> On Fri, Jan 27, 2012 at 06:31, sridhar bamandlapally
> <sridhar.bn1@gmail.com> wrote:
>> --------------------------------------------------------------------------
>> | Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time    
>> |
>> --------------------------------------------------------------------------
>> |   0 | SELECT STATEMENT  |      |  7444K|   944M| 16077   (4)| 00:03:13
>> |
>> |   1 |  TABLE ACCESS FULL| EMP  |  7444K|   944M| 16077   (4)| 00:03:13
>> |
>> --------------------------------------------------------------------------
>
> Sorry to take this off topic, but... Seriously, over 3 minutes to read
> 944 MB of data? That's less than 5 MB/s, what's wrong with your
> database? :)

Yes, those results are quite suspicious. There's probably something
interfering with the queries (other queries, different processes, block
cleanout, ...) or maybe this is purely due to caching.

sridhar, run the queries repeatedly and my quess is the difference will
disappear (and the fist query will be a bit faster I guess).

Tomas




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