Mailing-List: contact couchdb-user-help@incubator.apache.org; run by ezmlm
Precedence: bulk
Reply-To: couchdb-user@incubator.apache.org
Received-SPF: pass (athena.apache.org: domain of jchris@gmail.com designates
 209.85.146.183 as permitted sender)
DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=message-id:date:from:sender:to:subject:in-reply-to:mime-version
         :content-type:content-transfer-encoding:content-disposition
         :references:x-google-sender-auth;
        b=x+rZ3DTTt9qCzV6cY4V2QFaiMCQasKIB4P+YSyosGdxnIwngZbOodS9nWa7siSSMD4
         KlIiMix6pQYHgEYDxMbDtot3JnYEqTMfvg1NL4GTubbJgO5FSH1TobNQad8HYESWVluG
         ikfP7uayKViB8CBImFEnmIPQFZY79hySOUkBI=
Message-ID: <e282921e0806282238q481f62f1w464e016266bc1e3b@mail.gmail.com>
Date: Sat, 28 Jun 2008 22:38:42 -0700
From: "Chris Anderson" <jchris@grabb.it>
Sender: jchris@gmail.com
To: couchdb-user@incubator.apache.org
Subject: Re: General-understanding questions about views
In-Reply-To: <F778CE22-9DA1-4AF9-A1E2-A7C38AD94367@ketralnis.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
References: <3F12B537-F1E1-45A5-857E-53E8CD5EC73E@ketralnis.com>
	 <250C86A3-3F40-4C48-B05B-2ED9DCFF1109@apache.org>
	 <8BC12E79-6DDE-499B-9C81-49C891C0B42E@ketralnis.com>
	 <e282921e0806282048q55c46f05jf2d6eda6729d7034@mail.gmail.com>
	 <F778CE22-9DA1-4AF9-A1E2-A7C38AD94367@ketralnis.com>

On Sat, Jun 28, 2008 at 9:17 PM, David King <dking@ketralnis.com> wrote:
> But in the example I gave (that I got from the CouchDB wiki), there's no way
> for the reduction to be accurate in the face of deletions and modifications
> without re-calculating it for every single item in the database. That is,
> given a database of 5 million rows, every time one is modified or deleted
> (or possibly even added, depending on implementation), all 5 million rows
> have to pass through that function
>

Now you're getting to the technical part. This quote from Damien is
the best I can do for you:

http://damienkatz.net/2008/02/incremental_map_1.html

... in this design, the reductions happen at index-update time, and
the reductions are stored directly inside the inner nodes of the view
b+tree index. Then at query time, the intermediate results are reduced
to their final result. The number of reductions that happen at query
time are logarithmic with respect to the number of matching
key/values.


-- 
Chris Anderson
http://jchris.mfdz.com