Received: from localhost (unknown [200.46.208.211]) by mail.postgresql.org (Postfix) with ESMTP id 70629632E23 for ; Tue, 2 Jun 2009 11:38:42 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by localhost (mx1.hub.org [200.46.208.211]) (amavisd-maia, port 10024) with ESMTP id 92872-06 for ; Tue, 2 Jun 2009 11:38:31 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by mail.postgresql.org (Postfix) with ESMTP id 9D0886324E8 for ; Tue, 2 Jun 2009 11:38:40 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.14.2/8.14.2) with ESMTP id n52EcRh0011927; Tue, 2 Jun 2009 10:38:27 -0400 (EDT) To: Robert Haas cc: Simon Riggs , Ron Mayer , Euler Taveira de Oliveira , "pgsql-hackers@postgresql.org" Subject: Re: explain analyze rows=%.0f In-reply-to: References: <603c8f070905281830g2e5419c4xad2946d149e21f9d@mail.gmail.com> <4A1F4FD5.7060204@timbira.com> <4A249CE9.6050708@cheapcomplexdevices.com> <1243950060.23910.58.camel@ebony.2ndQuadrant> Comments: In-reply-to Robert Haas message dated "Tue, 02 Jun 2009 10:06:18 -0400" Date: Tue, 02 Jun 2009 10:38:27 -0400 Message-ID: <11926.1243953507@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=0.112 tagged_above=0 required=5 tests=AWL=0.112 X-Spam-Level: X-Archive-Number: 200906/148 X-Sequence-Number: 139203 Robert Haas writes: > On Jun 2, 2009, at 9:41 AM, Simon Riggs wrote: >> You're right that the number of significant digits already exceeds the >> true accuracy of the computation. I think what Robert wants to see is >> the exact value used in the calc, so the estimates can be checked more >> thoroughly than is currently possible. > Bingo. Uh, the planner's estimate *is* an integer. What was under discussion (I thought) was showing some fractional digits in the case where EXPLAIN ANALYZE is outputting a measured row count that is an average over multiple loops, and therefore isn't necessarily an integer. In that case the measured value can be considered arbitrarily precise --- though I think in practice one or two fractional digits would be plenty. regards, tom lane