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 3B6B74348 for ; Wed, 13 Jul 2011 09:08:55 +0000 (UTC) Received: (qmail 69259 invoked by uid 500); 13 Jul 2011 09:08:52 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 68959 invoked by uid 500); 13 Jul 2011 09:08:41 -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 68951 invoked by uid 99); 13 Jul 2011 09:08:39 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 13 Jul 2011 09:08:39 +0000 X-ASF-Spam-Status: No, hits=2.2 required=5.0 tests=HTML_MESSAGE,RCVD_IN_DNSWL_LOW,SPF_NEUTRAL X-Spam-Check-By: apache.org Received-SPF: neutral (athena.apache.org: local policy) Received: from [209.85.212.44] (HELO mail-vw0-f44.google.com) (209.85.212.44) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 13 Jul 2011 09:08:33 +0000 Received: by vws12 with SMTP id 12so6050449vws.31 for ; Wed, 13 Jul 2011 02:08:12 -0700 (PDT) MIME-Version: 1.0 Received: by 10.52.68.138 with SMTP id w10mr1003512vdt.43.1310548092722; Wed, 13 Jul 2011 02:08:12 -0700 (PDT) Received: by 10.52.162.135 with HTTP; Wed, 13 Jul 2011 02:08:12 -0700 (PDT) In-Reply-To: References: Date: Wed, 13 Jul 2011 12:08:12 +0300 Message-ID: Subject: Re: Why do Digest Queries return hash instead of timestamp? From: David Boxenhorn To: user@cassandra.apache.org Content-Type: multipart/alternative; boundary=20cf307f37e4871e6604a7efc1a3 --20cf307f37e4871e6604a7efc1a3 Content-Type: text/plain; charset=ISO-8859-1 If you have to pieces of data that are different but have the same timestamp, how can you resolve consistency? This is a pathological situation to begin with, why should you waste effort to (not) solve it? On Wed, Jul 13, 2011 at 12:05 PM, Boris Yen wrote: > I guess it is because the timestamp does not guarantee data consistency, > but hash does. > > Boris > > > On Wed, Jul 13, 2011 at 4:27 PM, David Boxenhorn wrote: > >> I just saw this >> >> http://wiki.apache.org/cassandra/DigestQueries >> >> and I was wondering why it returns a hash of the data. Wouldn't it be >> better and easier to return the timestamp? You don't really care what the >> data is, you only care whether it is more or less recent than another piece >> of data. >> > > --20cf307f37e4871e6604a7efc1a3 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable

If you have to pieces of data that are different but have = the same timestamp, how can you resolve consistency?

This is a path= ological situation to begin with, why should you waste effort to (not) solv= e it?

On Wed, Jul 13, 2011 at 12:05 PM, Boris Yen = <yulinyen@gmail.= com> wrote:

I guess it is because the timestamp does not guarantee data consistency, bu= t hash does.

Boris

On Wed, Jul 1= 3, 2011 at 4:27 PM, David Boxenhorn <david@citypath.com> wr= ote:

I just saw this

ht= tp://wiki.apache.org/cassandra/DigestQueries

and I was wondering why it returns a hash of the data. Wouldn't it = be better and easier to return the timestamp? You don't really care wha= t the data is, you only care whether it is more or less recent than another= piece of data.

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