Subject: Re: High CPU Load
From: =?ISO-8859-1?Q?J=E9r=F4me?= BENOIS <benois@argia-engineering.fr>
To: Dave Dutcher <dave@tridecap.com>
Cc: pgsql-performance@postgresql.org
In-Reply-To: <004001c6d80e$bdef5bc0$8300a8c0@tridecap.com>
References: <004001c6d80e$bdef5bc0$8300a8c0@tridecap.com>
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Date: Thu, 14 Sep 2006 17:09:25 +0200
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Hi Dave,
Le jeudi 14 septembre 2006 =C3=A0 10:02 -0500, Dave Dutcher a =C3=A9crit :
> > -----Original Message-----
> > From: pgsql-performance-owner@postgresql.org=20
> > [mailto:pgsql-performance-owner@postgresql.org] On Behalf Of=20
> > J=C3=A9r=C3=B4me BENOIS
> >=20
>  explain analyze select distinct
> > INTEGER_VALUE,DATE_VALUE,EI_ID,VALUE_TYPE,FLOAT_VALUE,ID,TEXT_
> > VALUE,CATEGORY_ID,STRING_VALUE,CATEGORYATTR_ID,NAME from (((=20
> > select distinct ei_id as EIID from mpng2_ei_attribute as=20
> > reqin1 where reqin1.CATEGORYATTR_ID =3D 0 AND reqin1.TEXT_VALUE=20
> > ilike '' and ei_id in ( select distinct ei_id as EIID from=20
> > mpng2_ei_attribute as reqin2 where reqin2.CATEGORYATTR_ID =3D 0=20
> > AND reqin2.TEXT_VALUE ilike '' and ei_id in ( select distinct=20
> > ei_id as EIID from mpng2_ei_attribute as reqin3 where=20
> > reqin3.NAME =3D '' AND reqin3.STRING_VALUE =3D '' ) ) ) ) ) as=20
> > req0 join mpng2_ei_attribute on req0.eiid =3D=20
> > mpng2_ei_attribute.ei_id order by ei_id asc;
>=20
>=20
> That is a lot of distinct's.  Sorts are one thing that can really use up
> CPU.  This query is doing lots of sorts, so its not surprising the CPU us=
age
> is high. =20
>=20
> On the subqueries you have a couple of cases where you say "... in (selec=
t
> distinct ...)"  I don=E2=80=99t think the distinct clause is necessary in=
 that case.
> I'm not a hundred percent sure, but you might want to try removing them a=
nd
> see if the query results are the same and maybe the query will execute
> faster.

Thanks for your advice, but the load was good with previous version of
postgres -> 7.4.6 on the same server and same datas, same application,
same final users ...

So we supect some system parameter, but which ?

With vmstat -s is showing a lot of "pages swapped out", have you an
idea ?

Thanls a lot,

--=20
J=C3=A9r=C3=B4me,

python -c "print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in 'sioneb@gnireenigne-aigra.rf'.split('@')])"

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