Mailing-List: contact user-help@couchdb.apache.org; run by ezmlm
Precedence: bulk
Reply-To: user@couchdb.apache.org
Received-SPF: pass (athena.apache.org: domain of couchdbuser@gmail.com
 designates 209.85.216.52 as permitted sender)
DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=mime-version:in-reply-to:references:date:message-id:subject:from:to
         :content-type;
        b=UuqMvbtpe67vswif0jL/UnIHL8iDqmi0FdhXqky/3+NoDEcn8kMtivM0C/2rw3ijli
         VK/GvVfP+xoqVTxZzjwCG1fmJMEx7TqwTiM5JeKu72fvJnSvDm5fuZWQZMyvY+LPGEs1
         +n7KH3/jyLOw373pqWwIPhXkfup2oFjaSMmaA=
MIME-Version: 1.0
In-Reply-To: <AANLkTi=FSvmgvVB1ZCjJcK03JfMvSuH8AYYJXZmkz2rW@mail.gmail.com>
References: <AANLkTimh5-2qraJkLaaWON6BnEvpEs6nW4yCk_H8ZD2G@mail.gmail.com>
	<AANLkTi=cdXpj39pDB476Ch2zQmKdwVJAXhz=vWXO_oyL@mail.gmail.com>
	<AANLkTi=FSvmgvVB1ZCjJcK03JfMvSuH8AYYJXZmkz2rW@mail.gmail.com>
Date: Sat, 6 Nov 2010 22:25:24 -0400
Message-ID: <AANLkTik_LzXNbwcYMwPmFkfGjLD+e766gJQcuGF_pdzk@mail.gmail.com>
Subject: Re: Write race conditions, working without _rev
From: couchdb user <couchdbuser@gmail.com>
To: user@couchdb.apache.org
Content-Type: text/plain; charset=ISO-8859-1

To follow up on what Chad said about avoiding reading the doc to get
the _rev, you can also use a HEAD request, while it is an extra
request, it will use a lot less resources.


$ curl -HEAD http://127.0.0.1:5984/example/post98
{"_id":"post98","_rev":"1-9e6543bfb3cbf3b7c36904a1ea4b806f","tags":"[2,5]"}

Regards,


On Sat, Nov 6, 2010 at 3:52 PM, Luciano Ramalho <luciano@ramalho.org> wrote:
> On Fri, Nov 5, 2010 at 2:03 PM, Paul Davis <paul.joseph.davis@gmail.com> wrote:
>> In the second case, the second person to write the document wins,
>> erasing any changes the first write's effects. The first writer will
>> then be in a state where his view of the database will be
>> inconsistent. The thing his, he can't know because without requiring a
>> _rev token he'll never get a notification of any sort of error.
>
> As I understand, the situation you describe above never happens in
> practice with CouchDB. A second PUT to the same document _id will
> always require the _rev attribute, so there's no way to overwrite a
> previous update by accident. This is one of the best features of
> CouchDB for document-oriented persistency.
>
>
> --
> Luciano Ramalho
> programador repentista || stand-up programmer
> Twitter: @luciano
>