From user-return-20688-apmail-cassandra-user-archive=cassandra.apache.org@cassandra.apache.org Mon Sep 12 16:45:53 2011 Return-Path: X-Original-To: apmail-cassandra-user-archive@www.apache.org Delivered-To: apmail-cassandra-user-archive@www.apache.org Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by minotaur.apache.org (Postfix) with SMTP id 55FDC7EA1 for ; Mon, 12 Sep 2011 16:45:53 +0000 (UTC) Received: (qmail 38301 invoked by uid 500); 12 Sep 2011 16:45:51 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 38238 invoked by uid 500); 12 Sep 2011 16:45:50 -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 38229 invoked by uid 99); 12 Sep 2011 16:45:50 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Mon, 12 Sep 2011 16:45:50 +0000 X-ASF-Spam-Status: No, hits=1.5 required=5.0 tests=FREEMAIL_FROM,HTML_MESSAGE,RCVD_IN_DNSWL_LOW,SPF_PASS,T_TO_NO_BRKTS_FREEMAIL X-Spam-Check-By: apache.org Received-SPF: pass (athena.apache.org: domain of davidj@gmail.com designates 209.85.161.172 as permitted sender) Received: from [209.85.161.172] (HELO mail-gx0-f172.google.com) (209.85.161.172) by apache.org (qpsmtpd/0.29) with ESMTP; Mon, 12 Sep 2011 16:45:44 +0000 Received: by gxk19 with SMTP id 19so131015gxk.31 for ; Mon, 12 Sep 2011 09:45:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :content-type; bh=S+Iuf2SQf9Xxe33H0tv9dLuniMyiTIQqnTcjbZMwHc4=; b=Iyf/1Shy0kltNoznd0BNG9kak4NRYMIlfpnvid1GPB2MW3ToU1cXTkRUgjNrs5tAfs 4eAm/T1F20Jvmge1C5a8vzlwusFV6nqxL/nRI1doNVtL8HKG2MC3BwnZNZMykAM3gCDI BU99GUxcAfYN4BYWsnx6yZjv/khlbeDuknXlk= Received: by 10.231.82.10 with SMTP id z10mr7390083ibk.77.1315845924096; Mon, 12 Sep 2011 09:45:24 -0700 (PDT) MIME-Version: 1.0 Received: by 10.231.36.11 with HTTP; Mon, 12 Sep 2011 09:45:04 -0700 (PDT) In-Reply-To: References: From: David Jeske Date: Mon, 12 Sep 2011 09:45:04 -0700 Message-ID: Subject: Re: Not all data structures need timestamps (and don't require wasted memory). To: user@cassandra.apache.org Content-Type: multipart/alternative; boundary=000e0cdf41f2e28b9a04acc14097 --000e0cdf41f2e28b9a04acc14097 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable On Sat, Sep 3, 2011 at 8:26 PM, Kevin Burton wrote: > The point is that replication in Cassandra only needs timestamps to handl= e > out of order writes =85 for values that are idempotent, this isn't necess= ary. > The order doesn't matter. > I believe this is a mis-understanding of how idempotency applies to Cassandra replication. If there were no timestamps stored, how would read-repair work? There would be two different values with no way to tell which was written second. --000e0cdf41f2e28b9a04acc14097 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable
On Sat, Sep 3, 2011 at 8:26 PM, Kevin Burton <burton@spinn3r.com= > wrote:
The point is that replication in Cassandra only needs timestamps to ha= ndle out of order writes =85 for values that are idempotent, this isn't= necessary. =A0The order doesn't matter.

I believe this is a mis-understanding of how idempotency applies to Ca= ssandra replication. If there were no timestamps stored, how would read-rep= air work? There would be two different values with no way to tell which was= written second.
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