Received: from maia.hub.org (maia-2.hub.org [200.46.204.251]) by mail.postgresql.org (Postfix) with ESMTP id 33D666338C4 for ; Sun, 6 Jun 2010 07:30:27 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.251]) (amavisd-maia, port 10024) with ESMTP id 35638-08 for ; Sun, 6 Jun 2010 10:30:19 +0000 (UTC) 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 F4200633663 for ; Sun, 6 Jun 2010 07:30:19 -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 o56AUF3C017328; Sun, 6 Jun 2010 06:30:15 -0400 (EDT) To: Greg Smith cc: pgsql-docs@postgresql.org Subject: Re: Special column trivia In-reply-to: <4C0B4BE1.9060001@2ndquadrant.com> References: <4C0B4BE1.9060001@2ndquadrant.com> Comments: In-reply-to Greg Smith message dated "Sun, 06 Jun 2010 03:18:57 -0400" Date: Sun, 06 Jun 2010 06:30:15 -0400 Message-ID: <17327.1275820215@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-1.91 tagged_above=-5 required=5 tests=BAYES_00=-1.9, T_RP_MATCHES_RCVD=-0.01 X-Spam-Level: X-Archive-Number: 201006/7 X-Sequence-Number: 5575 Greg Smith writes: > I was just reading > http://www.postgresql.org/docs/9.0/static/ddl-system-columns.html and > noted that the second part about the ctid being unstable: "a row's ctid > will change if it is updated or moved by VACUUM FULL" is probably not > true anymore. Is that worth updating? It's still true. VACUUM FULL still reassigns ctids. > What got me reading that section was a rather weird documentation > question/addition from Edmund Horner. He noted that the following works > on PG8.4 and 9.0: > postgres=# select (row(1,2)).name; This is the cast-a-composite-type-to-string-type issue that's come up in several guises before, eg most recently at http://archives.postgresql.org/pgsql-general/2010-05/msg01126.php regards, tom lane