Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1WfwWQ-0002iX-7y for pgsql-performance@arkaria.postgresql.org; Thu, 01 May 2014 19:19:54 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.80) (envelope-from ) id 1WfwWP-0008R5-OC for pgsql-performance@arkaria.postgresql.org; Thu, 01 May 2014 19:19:53 +0000 Received: from makus.postgresql.org ([2001:4800:7903:4::125]) by malur.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1WfwWO-0008Qi-PG for pgsql-performance@postgresql.org; Thu, 01 May 2014 19:19:52 +0000 Received: from prod2.officenet.no ([195.159.87.246]) by makus.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1WfwWG-0002sj-K2 for pgsql-performance@postgresql.org; Thu, 01 May 2014 19:19:52 +0000 Received: from localhost ([127.0.0.1] helo=prod2) by prod2.officenet.no with esmtp (Exim 4.76) (envelope-from ) id 1WfwUC-0003WM-Ik for pgsql-performance@postgresql.org; Thu, 01 May 2014 21:17:36 +0200 Date: Thu, 1 May 2014 21:17:36 +0200 (CEST) From: Andreas Joseph Krogh To: pgsql-performance@postgresql.org Message-ID: In-Reply-To: <536293DB.4010505@functor.nl> Subject: Re: Optimize query for listing un-read messages MIME-Version: 1.0 X-Mailer: OfficeNet Mail 1.9.0-SNAPSHOT X-Pg-Spam-Score: -0.5 (/) Content-Type: multipart/related; boundary="----=_Part_26_773401974.1398971856132" List-Archive: List-Help: List-ID: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: X-Mailing-List: pgsql-performance Precedence: bulk Sender: pgsql-performance-owner@postgresql.org ------=_Part_25_319095619.1398971856132 Content-Type: multipart/related; boundary="----=_Part_26_773401974.1398971856132" ------=_Part_26_773401974.1398971856132 Content-Type: multipart/alternative; boundary="----=_Part_27_1029263732.1398971856149" ------=_Part_27_1029263732.1398971856149 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable P=C3=A5 torsdag 01. mai 2014 kl. 20:35:07, skrev Jochem Berndsen >:=20 Hi Andreas, [New to this list, forgive my ignorance.] [snip] I'm getting better performance with: SELECT m.id AS message_id, 1 AS person_id, FALSE AS is_read, m.subject FROM message m WHERE 1 =3D 1 AND NOT EXISTS(SELECT =C2=A0 =C2=A0 =C2=A0* =C2=A0 =C2=A0 =C2=A0FROM message_property pr =C2=A0 =C2=A0 =C2=A0WHERE pr.message_id =3D m.id AND pr.person_id =3D 1 AN= D pr.is_read); You then lose the distinction between message_property with is_read =3D FALSE, and nonexistent message_property for the message row. If that is essential, I'm getting a roughly 2x speedup on my non-tuned PostgreSQL with: =C2=A0 SELECT =C2=A0 =C2=A0 =C2=A0m.id=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 AS message_id, =C2=A0 =C2=A0 =C2=A0prop.person_id, =C2=A0 =C2=A0 =C2=A0coalesce(prop.is_read, FALSE) AS is_read, =C2=A0 =C2=A0 =C2=A0m.subject FROM message m =C2=A0 =C2=A0 =C2=A0LEFT OUTER JOIN message_property prop ON prop.message_= id =3D m.id AND prop.person_id =3D 1 WHERE not coalesce(prop.is_read, false); =C2=A0 =C2=A0 Hi Jochem, =C2=A0 T= hansk for looking=20 at it. I'm still seing ~500ms being spent and I was hoping for a way to do = this=20 using index so one could achieve 1-10ms, but maybe that's impossible given = the=20 schema? =C2=A0 Is there a way to design an equivalent=C2=A0 schema to achie= ve <10ms=20 execution-time? =C2=A0 -- Andreas Jospeh Krogh CTO / Partner - Visena AS Mo= bile: +47=20 909 56 963 andreas@visena.com www.visena.com=20 =C2=A0 ------=_Part_27_1029263732.1398971856149 Content-Type: text/html;charset=UTF-8 Content-Transfer-Encoding: quoted-printable
P=C3=A5 torsdag 01. mai 2014 kl. 20:35:07, skrev Jochem Berndsen <<= a href=3D"mailto:jochem@functor.nl" target=3D"_blank">jochem@functor.nl= >:
Hi Andreas,

[New to this list, forgive my ignorance.]
[snip]
I'm getting better performance with:

SELECT
m.id AS message_id,
1 AS person_id,
FALSE AS is_read,
m.subject
FROM message m
WHERE 1 =3D 1
AND NOT EXISTS(SELECT
=C2=A0 =C2=A0 =C2=A0*
=C2=A0 =C2=A0 =C2=A0FROM message_property pr
=C2=A0 =C2=A0 =C2=A0WHERE pr.message_id =3D m.id AND pr.person_id =3D 1 AND= pr.is_read);

You then lose the distinction between message_property with is_read =3D
FALSE, and nonexistent message_property for the message row.

If that is essential, I'm getting a roughly 2x speedup on my non-tuned
PostgreSQL with:
=C2=A0 SELECT
=C2=A0 =C2=A0 =C2=A0m.id=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 AS message_id,
=C2=A0 =C2=A0 =C2=A0prop.person_id,
=C2=A0 =C2=A0 =C2=A0coalesce(prop.is_read, FALSE) AS is_read,
=C2=A0 =C2=A0 =C2=A0m.subject
FROM message m
=C2=A0 =C2=A0 =C2=A0LEFT OUTER JOIN message_property prop ON prop.message_i= d =3D m.id AND
prop.person_id =3D 1
WHERE not coalesce(prop.is_read, false);
=C2=A0
=C2=A0
Hi Jochem,
=C2=A0
Thansk for looking at it. I'm still seing ~500ms being spent and I was= hoping for a way to do this using index so one could achieve 1-10ms, but m= aybe that's impossible given the schema?
=C2=A0
Is there a way to design an equivalent=C2=A0 schema to achieve <10m= s execution-time?
=C2=A0
--
Andrea= s Jospeh Krogh
CTO / Partner<= /span> - Visena AS
Mobile: +47 90= 9 56 963
3D""
=C2=A0
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