Return-Path: Delivered-To: apmail-couchdb-user-archive@www.apache.org Received: (qmail 62990 invoked from network); 9 Apr 2010 20:31:29 -0000 Received: from unknown (HELO mail.apache.org) (140.211.11.3) by 140.211.11.9 with SMTP; 9 Apr 2010 20:31:29 -0000 Received: (qmail 39370 invoked by uid 500); 9 Apr 2010 20:31:27 -0000 Delivered-To: apmail-couchdb-user-archive@couchdb.apache.org Received: (qmail 39327 invoked by uid 500); 9 Apr 2010 20:31:27 -0000 Mailing-List: contact user-help@couchdb.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: user@couchdb.apache.org Delivered-To: mailing list user@couchdb.apache.org Received: (qmail 39319 invoked by uid 99); 9 Apr 2010 20:31:27 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Fri, 09 Apr 2010 20:31:27 +0000 X-ASF-Spam-Status: No, hits=2.2 required=10.0 tests=FREEMAIL_ENVFROM_END_DIGIT,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE,SPF_PASS,T_TO_NO_BRKTS_FREEMAIL X-Spam-Check-By: apache.org Received-SPF: pass (nike.apache.org: domain of milu71@gmx.de designates 213.165.64.20 as permitted sender) Received: from [213.165.64.20] (HELO mail.gmx.net) (213.165.64.20) by apache.org (qpsmtpd/0.29) with SMTP; Fri, 09 Apr 2010 20:31:18 +0000 Received: (qmail invoked by alias); 09 Apr 2010 20:30:57 -0000 Received: from f054059086.adsl.alicedsl.de (EHLO wladimir) [78.54.59.86] by mail.gmx.net (mp043) with SMTP; 09 Apr 2010 22:30:57 +0200 X-Authenticated: #48488578 X-Provags-ID: V01U2FsdGVkX18XJxNsFKUX99Y+gvrqxg2bWLi6PMto9QZrdSdfMp M9tPQkFTtEI3pN Received: by wladimir (sSMTP sendmail emulation); Fri, 09 Apr 2010 22:30:37 +0200 Date: Fri, 9 Apr 2010 22:30:37 +0200 From: Michael Ludwig To: user@couchdb.apache.org Subject: Re: About denormalization and keep consistent Message-ID: <20100409203037.GB840@wladimir> References: <641CEC1C-ECF8-479C-8603-622D1FA8E8D3@gmail.com> <0676CAF7-68E8-467B-BE37-9F6F52BC79AC@gmail.com> <20100409195957.GA840@wladimir> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.2i X-Y-GMX-Trusted: 0 X-FuHaFi: 0.58999999999999997 X-Virus-Checked: Checked by ClamAV on apache.org Andrew Melo schrieb am 09.04.2010 um 15:04:59 (-0500) [Re: About denormalization and keep consistent]: > > Are there scenarios where writing happens to an SQL server, from > > where NoSQL replicas are fed and used to serve readers? > > Possibly. But, if you're writing to a single SQL master, then you lose > two benefits of Couch: horizontally scalable writes and not having to > be restricted by SQL's data model. You could do (for instance) single > master writes and many-slave reads on a stock SQL server in that case. Thanks, Andrew. It appears Faust is concerned about data consistency which is usually and easily ensured by suitable SQL data modeling. That does not happen to be the forte of a system designed for scalability at the expense of consistency. Faust, there are many places and cases where data can be copied and held redundantly in hundreds or thousands of places, and it simply doesn't matter. Think email, for example. If you changed the name belonging to your email address to "Johann Faust", it wouldn't matter that there are mails with the older version of your name in the archive, and they wouldn't have to be updated, and they even shouldn't be updated. That seems to be an excellent use case for a system like CouchDB. If, on the other hand, you care about consistency in the way you described, you might want to consider using a system that supports you in guaranteeing such consistency. -- Michael Ludwig