Received: from malur.postgresql.org ([217.196.149.56])
	by arkaria.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256)
	(Exim 4.89)
	(envelope-from <pgsql-performance-owner+archive@lists.postgresql.org>)
	id 1iAzeD-0005VV-NO
	for pgsql-performance@arkaria.postgresql.org; Thu, 19 Sep 2019 16:51:13 +0000
Received: from localhost ([127.0.0.1] helo=malur.postgresql.org)
	by malur.postgresql.org with esmtp (Exim 4.89)
	(envelope-from <pgsql-performance-owner+archive@lists.postgresql.org>)
	id 1iAzeC-0006eo-Kk
	for pgsql-performance@arkaria.postgresql.org; Thu, 19 Sep 2019 16:51:12 +0000
Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29])
	by malur.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256)
	(Exim 4.89)
	(envelope-from <luisroberto@siscobra.com.br>)
	id 1iAzeC-0006eM-BQ
	for pgsql-performance@lists.postgresql.org; Thu, 19 Sep 2019 16:51:12 +0000
Received: from hm1831-n-121.locaweb.com.br ([189.126.112.121])
	by magus.postgresql.org with esmtp (Exim 4.89)
	(envelope-from <luisroberto@siscobra.com.br>)
	id 1iAze6-0002sq-Qx
	for pgsql-performance@lists.postgresql.org; Thu, 19 Sep 2019 16:51:10 +0000
Received: from mcbain0016.correio.biz (201.76.49.39) by
 hm1831-n-113.locaweb.com.br id hgeouq15ctou for
 <pgsql-performance@lists.postgresql.org>;
 Thu, 19 Sep 2019 13:50:46 -0300 (envelope-from <luisroberto@siscobra.com.br>)
Received: from proxy.email-ssl.com.br (bartf0031.email.locaweb.com.br
 [10.31.120.63])
	by mcbain0016.correio.biz (Postfix) with ESMTP id D5910AA0343
	for <pgsql-performance@lists.postgresql.org>;
 Thu, 19 Sep 2019 13:50:56 -0300 (-03)
x-locaweb-id: 
 qyHzKK_R8aWhjwoIerpCUhsi5PfCUymhK53qXIAegdcRogeYX3-XTadcSpgGGxitWQf3rKGbFuqvLmn5XdJ_XeDnSC7FYZn7HbLXpGF-9IgCFmgQGgrxCDEo15F9LB44OnsLfXjEQNdayh8qp-s9AotEt2KUQ2RJBl9oRDY6_jQGONTy23UbTLyu956pUuVT8UlUgaIM6XARSVi84RGoZ3y_BYb-aN8PXpaI7MRvykI=
 NmM3NTY5NzM3MjZmNjI2NTcyNzQ2ZjQwNzM2OTczNjM2ZjYyNzI2MTJlNjM2ZjZkMmU2Mjcy
X-LocaWeb-COR: locaweb_2009_x-mail
X-AuthUser: luisroberto@siscobra.com.br
Received: from [192.168.0.42] (unknown [189.45.198.123])
	(Authenticated sender: luisroberto@siscobra.com.br)
	by proxy.email-ssl.com.br (Postfix) with ESMTPSA id 9A9B8B012D5
	for <pgsql-performance@lists.postgresql.org>;
 Thu, 19 Sep 2019 13:50:58 -0300 (-03)
Subject: Slow query on a one-tuple table
To: pgsql-performance@lists.postgresql.org
References: 
 <CA+t6e1kacbVHq69aihEVeBzH_nMY5eK7bZ-UXL_FuUquEgF_gg@mail.gmail.com>
 <24571.1568910502@sss.pgh.pa.us>
From: =?UTF-8?Q?Lu=c3=ads_Roberto_Weck?= <luisroberto@siscobra.com.br>
Message-ID: <774d6080-d6d7-e9e7-7351-9a412c7d5956@siscobra.com.br>
Date: Thu, 19 Sep 2019 13:55:46 -0300
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101
 Thunderbird/60.9.0
MIME-Version: 1.0
In-Reply-To: <24571.1568910502@sss.pgh.pa.us>
Content-Type: multipart/alternative;
 boundary="------------C79B9342E780E9287C0EC587"
Content-Language: pt-BR
List-Id: <pgsql-performance.lists.postgresql.org>
List-Help: <https://lists.postgresql.org/manage/>
List-Subscribe: <https://lists.postgresql.org/manage/>
List-Post: <mailto:pgsql-performance@lists.postgresql.org>
List-Owner: <mailto:pgsql-performance-owner@lists.postgresql.org>
List-Archive: <https://www.postgresql.org/list/pgsql-performance>
Precedence: bulk

This is a multi-part message in MIME format.
--------------C79B9342E780E9287C0EC587
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit

Hi!

I have a query that SELECT's only one tuple using a PK 
(https://explain.depesz.com/s/Hskt) <https://explain.depesz.com/s/Hskt>

the field I am selecting are a bigint and a text. Why does it read 1095 
shared buffers read?

If I adda LIMIT 1 clause, the query runs much faster: 
https://explain.depesz.com/s/bSZn

This table has only one tuple anyway, so I can't understand why does it 
takes so long without the LIMIT 1.
<https://explain.depesz.com/s/Hskt>

--------------C79B9342E780E9287C0EC587
Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: 7bit

<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
  </head>
  <body text="#000000" bgcolor="#FFFFFF">
    Hi!<br>
    <br>
    I have a query that SELECT's only one tuple using a PK (<a
      href="https://explain.depesz.com/s/Hskt">https://explain.depesz.com/s/Hskt)
    </a><br>
    <br>
    the field I am selecting are a bigint and a text. Why does it read
    1095 shared buffers read? <br>
    <br>
    If I adda LIMIT 1 clause, the query runs much faster: <a
      href="https://explain.depesz.com/s/bSZn">https://explain.depesz.com/s/bSZn</a><br>
    <br>
    This table has only one tuple anyway, so I can't understand why does
    it takes so long without the LIMIT 1.<br>
    <a href="https://explain.depesz.com/s/Hskt"></a>
  </body>
</html>

--------------C79B9342E780E9287C0EC587--