Return-Path: Delivered-To: apmail-cassandra-user-archive@www.apache.org Received: (qmail 55192 invoked from network); 2 Feb 2011 22:47:10 -0000 Received: from hermes.apache.org (HELO mail.apache.org) (140.211.11.3) by minotaur.apache.org with SMTP; 2 Feb 2011 22:47:10 -0000 Received: (qmail 76273 invoked by uid 500); 2 Feb 2011 22:47:06 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 75638 invoked by uid 500); 2 Feb 2011 22:47:06 -0000 Mailing-List: contact user-help@cassandra.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: user@cassandra.apache.org Delivered-To: mailing list user@cassandra.apache.org Received: (qmail 75577 invoked by uid 500); 2 Feb 2011 22:47:05 -0000 Delivered-To: apmail-incubator-cassandra-user@incubator.apache.org Received: (qmail 75567 invoked by uid 99); 2 Feb 2011 22:47:05 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 02 Feb 2011 22:47:05 +0000 X-ASF-Spam-Status: No, hits=-0.0 required=5.0 tests=RCVD_IN_DNSWL_LOW,SPF_NEUTRAL X-Spam-Check-By: apache.org Received-SPF: neutral (athena.apache.org: local policy) Received: from [209.85.218.47] (HELO mail-yi0-f47.google.com) (209.85.218.47) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 02 Feb 2011 22:46:57 +0000 Received: by yie16 with SMTP id 16so236653yie.6 for ; Wed, 02 Feb 2011 14:46:34 -0800 (PST) MIME-Version: 1.0 Received: by 10.151.45.17 with SMTP id x17mr11674058ybj.304.1296686794486; Wed, 02 Feb 2011 14:46:34 -0800 (PST) Sender: scode@scode.org Received: by 10.151.79.21 with HTTP; Wed, 2 Feb 2011 14:46:34 -0800 (PST) X-Originating-IP: [213.114.156.79] In-Reply-To: <1296679454477-5986442.post@n2.nabble.com> References: <1296660931172-5985214.post@n2.nabble.com> <1296679454477-5986442.post@n2.nabble.com> Date: Wed, 2 Feb 2011 23:46:34 +0100 X-Google-Sender-Auth: Li4oLMmKUcL3nszsRLzpmVuapjg Message-ID: Subject: Re: Counters in 0.8 -- conditional? From: Peter Schuller To: user@cassandra.apache.org Cc: cassandra-user@incubator.apache.org Content-Type: text/plain; charset=UTF-8 > Thanks. Just wanted to note that counting the number of rows where foo=bar is > a fairly ubiquitous task in db applications. In case of "big data", > trafficking all these data to client just to count something isn't optimal > at all. You can ask Cassandra to do the counting, but the cost is still going to involve reading the data on the Cassandra end. Hence, O(n) rather than O(1). (It would obviously be nice if counts could be done O(1), but it's not trivial to implement or obvious how to do it in order for it to be generally useful. Even non-distributed databases like PostgreSQL have issues with that.) -- / Peter Schuller