X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [64.117.224.130]) by svr1.postgresql.org (Postfix) with ESMTP id 0195AD1F05A for ; Thu, 14 Aug 2003 18:00:51 +0000 (GMT) Received: from svr1.postgresql.org ([64.117.224.193]) by localhost (neptune.hub.org [64.117.224.130]) (amavisd-new, port 10024) with ESMTP id 10958-10 for ; Thu, 14 Aug 2003 15:00:41 -0300 (ADT) Received: from sss.pgh.pa.us (unknown [192.204.191.242]) by svr1.postgresql.org (Postfix) with ESMTP id CA1BFD1F413 for ; Thu, 14 Aug 2003 15:00:20 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.12.9/8.12.9) with ESMTP id h7EI0L5H006312; Thu, 14 Aug 2003 14:00:21 -0400 (EDT) To: Jan Wieck Cc: Scott Cain , PgSQL Performance ML , pgsql-sql@postgresql.org Subject: Re: [SQL] EXTERNAL storage and substring on long strings In-reply-to: <3F3BA49D.9070405@Yahoo.com> References: <1059679600.1429.41.camel@localhost.localdomain> <3F297CBA.1080703@joeconway.com> <1059686498.7505.558.camel@haggis> <1060010735.1433.26.camel@localhost.localdomain> <3574.1060012423@sss.pgh.pa.us> <3F3BA49D.9070405@Yahoo.com> Comments: In-reply-to Jan Wieck message dated "Thu, 14 Aug 2003 11:02:53 -0400" Date: Thu, 14 Aug 2003 14:00:21 -0400 Message-ID: <6311.1060884021@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: by amavisd-new at postgresql.org X-Archive-Number: 200308/265 X-Sequence-Number: 3081 Jan Wieck writes: > Doesn't look that unrealistic to me. A plain text based substring > function will reassemble the whole beast first before cutting out the > wanted part. His manually chunked version will read only those chunks > needed. So does substr(), if applied to EXTERNAL (non-compressed) toasted text. See John Gray's improvements a release or two back. regards, tom lane