Received: from malur.postgresql.org ([217.196.149.56])
 by arkaria.postgresql.org with esmtp (Exim 4.80) (envelope-from
 <pgsql-performance-owner+M52222=pgsql-performance-ar@postgresql.org>)
 id 1XWWpv-0006ix-9s
 for pgsql-performance@arkaria.postgresql.org; Tue, 23 Sep 2014 20:37:23 +0000
Received: from localhost ([127.0.0.1] helo=postgresql.org)
 by malur.postgresql.org with smtp (Exim 4.80) (envelope-from
 <pgsql-performance-owner+M52222=pgsql-performance-ar@postgresql.org>)
 id 1XWWpu-0008Mq-LZ
 for pgsql-performance@arkaria.postgresql.org; Tue, 23 Sep 2014 20:37:22 +0000
Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29])
 by malur.postgresql.org with esmtps (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256)
 (Exim 4.80) (envelope-from <emilu@encs.concordia.ca>)
 id 1XWWpt-0008Mj-G0
 for pgsql-performance@postgresql.org; Tue, 23 Sep 2014 20:37:21 +0000
Received: from oldperseverance.encs.concordia.ca ([132.205.96.92])
 by magus.postgresql.org with esmtp (Exim 4.80)
 (envelope-from <emilu@encs.concordia.ca>) id 1XWWpp-0003vH-VU
 for pgsql-performance@postgresql.org; Tue, 23 Sep 2014 20:37:20 +0000
Received: from cacao.encs.concordia.ca (emilu@cacao.encs.concordia.ca
 [132.205.47.225])
 by oldperseverance.encs.concordia.ca (envelope-from emilu@encs.concordia.ca)
 (8.13.7/8.13.7) with ESMTP id s8NKbF2c004623
 for <pgsql-performance@postgresql.org>; Tue, 23 Sep 2014 16:37:15 -0400
Message-ID: <5421D9FB.2030008@encs.concordia.ca>
Date: Tue, 23 Sep 2014 16:37:15 -0400
From: Emi Lu <emilu@encs.concordia.ca>
Reply-To: emilu@encs.concordia.ca
User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64;
 rv:24.0) Gecko/20100101 Thunderbird/24.8.0
MIME-Version: 1.0
To: "pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Which update action quicker?
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
X-Scanned-By: MIMEDefang 2.58 on oldperseverance.encs.concordia.ca at
 2014/09/23 16:37:15 EDT
X-Pg-Spam-Score: -1.9 (-)
List-Archive: <http://archives.postgresql.org/pgsql-performance>
List-Help: <mailto:majordomo@postgresql.org?body=help>
List-ID: <pgsql-performance.postgresql.org>
List-Owner: <mailto:pgsql-performance-owner@postgresql.org>
List-Post: <mailto:pgsql-performance@postgresql.org>
List-Subscribe: <mailto:majordomo@postgresql.org?body=sub%20pgsql-performance>
List-Unsubscribe: 
 <mailto:majordomo@postgresql.org?body=unsub%20pgsql-performance>
X-Mailing-List: pgsql-performance
Precedence: bulk
Sender: pgsql-performance-owner@postgresql.org

<html>
  <head>

    <meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">
  </head>
  <body bgcolor="#FFFFFF" text="#000000">
    <div class="moz-text-flowed" style="font-size: 18px;"
      lang="x-western"><small>Hello list,
        <br>
        <br>
        For a big table with more than 1,000,000 records, may I know
        which update is quicker please?
        <br>
        <br>
        (1) update t1
        <br>
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; set c1 = a.c1
        <br>
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; from a
        <br>
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; where pk and
        <br>
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; t1.c1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &lt;&gt; a.c1;
        <br>
        &nbsp;......
        <br>
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; update t1
        <br>
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; set c_N = a.c_N
        <br>
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; from a
        <br>
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; where pk and
        <br>
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; t1.c_N&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &lt;&gt; a.c_N;
        <br>
        <br>
        <br>
        (2)&nbsp; update t1
        <br>
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; set c1 = a.c1 ,
        <br>
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; c2&nbsp; = a.c2,
        <br>
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ...
        <br>
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; c_N = a.c_N
        <br>
        &nbsp;&nbsp;&nbsp;&nbsp; from a
        <br>
        &nbsp;&nbsp;&nbsp;&nbsp; where pk AND
        <br>
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (&nbsp; t1.c1 &lt;&gt; a.c1 OR t1.c2 &lt;&gt;
        a.c2..... t1.c_N &lt;&gt; a.c_N)
        <br>
        <br>
        <br>
        Or other quicker way for update action?
        <br>
        <br>
        Thank you
        <br>
        Emi
      </small><br>
    </div>
  </body>
</html>