Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1WvdQf-0002fe-6e for pgsql-performance@arkaria.postgresql.org; Sat, 14 Jun 2014 02:10:49 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.80) (envelope-from ) id 1WvdQe-0001kN-F8 for pgsql-performance@arkaria.postgresql.org; Sat, 14 Jun 2014 02:10:48 +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 ) id 1Wtdcm-0002MQ-Ng for pgsql-performance@postgresql.org; Sun, 08 Jun 2014 13:59:04 +0000 Received: from sam.nabble.com ([216.139.236.26]) by magus.postgresql.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:256) (Exim 4.80) (envelope-from ) id 1Wtdch-0007Ho-9i for pgsql-performance@postgresql.org; Sun, 08 Jun 2014 13:59:03 +0000 Received: from [192.168.236.26] (helo=sam.nabble.com) by sam.nabble.com with esmtp (Exim 4.72) (envelope-from ) id 1Wtdcd-0004J3-Hw for pgsql-performance@postgresql.org; Sun, 08 Jun 2014 06:58:55 -0700 Date: Sun, 8 Jun 2014 06:58:55 -0700 (PDT) From: pinker To: pgsql-performance@postgresql.org Message-ID: <1402235935505-5806445.post@n5.nabble.com> In-Reply-To: References: <4D00B4DE.3030508@xgs-france.com> Subject: Re: UNION and bad performance MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Pg-Spam-Score: -0.8 (/) 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 >> rhaas=# explain select a from generate_series(1,100) a union select a >> from generate_series(1,100) a; >> QUERY PLAN >> -------------------------------------------------------------------------------------- >> HashAggregate (cost=45.00..65.00 rows=2000 width=4) >> -> Append (cost=0.00..40.00 rows=2000 width=4) Why in this case the estimated number of rows is 2000? Is it standard planner behavior? -- View this message in context: http://postgresql.1045698.n5.nabble.com/UNION-and-bad-performance-tp3301375p5806445.html Sent from the PostgreSQL - performance mailing list archive at Nabble.com. -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance