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Re: statement stuck when the connection grew up to 45 or more

From: "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>
To: kah_hang_ang(at)toray(dot)com(dot)my
Cc: Jan Cruz <malebug(at)gmail(dot)com>, Qingqing Zhou <zhouqq(at)cs(dot)toronto(dot)edu>,pgsql-bugs(at)postgresql(dot)org
Subject: Re: statement stuck when the connection grew up to 45 or more
Date: 2006-06-09 17:33:29
Message-ID: 20060609173329.GY45331@pervasive.com (view raw or flat)
Thread:
Lists: pgsql-bugs
On Fri, Jun 09, 2006 at 05:29:08PM +0800, kah_hang_ang(at)toray(dot)com(dot)my wrote:
> I had check using ps -auxw|grep postgres & using select * from
> pg_stat_activity
> and it shows that the is really running and use 99% of the CPU.
> 
> Is there any wrong with the query?
> As suggested by Jan Cruz, it is to fine tune the performance of the query.
> Even if I not fine tune the query it should able to run without problem.
> 
> What I not understand is why this query stuck when the connection growth up
> to certain limit.
> 
> I did try execute the query with the connection more than 45 and it really
> stuck there.
> I wait for around 10 minutes but it still running.

Was the box swapping during this time? What are the specs on the
machine?

> I kill about 10 connections then the query start to run and finish within
> 30 sec.
> 
> May I know what will be the possible cause of this problem?
> 
> Regards,
> KH Ang
> 
> 
> 
>                                                                                                                                           
>                       "Jan Cruz"                                                                                                          
>                       <malebug(at)gmail(dot)com>         To:       "Qingqing Zhou" <zhouqq(at)cs(dot)toronto(dot)edu>                                       
>                       Sent by:                    cc:       pgsql-bugs(at)postgresql(dot)org                                                     
>                       pgsql-bugs-owner(at)pos        Subject:  Re: [BUGS] statement stuck when the connection grew up to 45 or more          
>                       tgresql.org                                                                                                         
>                                                                                                                                           
>                                                                                                                                           
>                       06/02/2006 03:08 PM                                                                                                 
>                                                                                                                                           
>                                                                                                                                           
> 
> 
> 
> 
> This is the statement which having problem:
>      select count(distinct empno) as counter1 from pay_master_history
>            where empno in (select empno from pay_batch_basic_history where
> organizationid like '015003%')
>      and processyear = '2006'
>      and processmonth = '05'
>      and processbatch = '1'
> 
> SELECT COUNT (*) FROM (
> SELECT empno as counter1 from pay_master_history as a
> INNER JOIN (select empno from pay_batch_basic_history where organizationid
> like '015003%'      and processyear = '2006'
>      and processmonth = '05'
>      and processbatch = '1') as b
> ON b.empno = a.empno ) as count_result
> -----------------------------
> or just create the view and use inner join then count :b
> 
> 
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 5: don't forget to increase your free space map settings
> 

-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby(at)pervasive(dot)com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461

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