Mailing-List: contact user-help@couchdb.apache.org; run by ezmlm
Precedence: bulk
Reply-To: user@couchdb.apache.org
Received-SPF: pass (nike.apache.org: domain of sebastiancohnen@googlemail.com
 designates 209.85.220.209 as permitted sender)
DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=googlemail.com; s=gamma;
        h=subject:mime-version:content-type:from:in-reply-to:date
         :content-transfer-encoding:message-id:references:to:x-mailer;
        b=nmExLxiuZsFKUquVV+9O1pY11bzBHvNiigJlRZGqR479G/YMcXcrVAkhBAhWBsAIaU
         ChGnFCRjMupeGPB7tVL0SWEDtwyQJiozxkgqqfSpmLwhyQiRHSIwIVoW3Cv73stmSYI0
         dXSNy5qg0eXZmXTTsSTqcLAgYMDAdkAd0Ufis=
Subject: Re: key entropy and view performance
Mime-Version: 1.0 (Apple Message framework v1077)
Content-Type: text/plain; charset=us-ascii
From: Sebastian Cohnen <sebastiancohnen@googlemail.com>
In-Reply-To: <2fd53c3a1002220300s293ee858r9400dfa4b07f9b3a@mail.gmail.com>
Date: Mon, 22 Feb 2010 13:24:10 +0100
Content-Transfer-Encoding: quoted-printable
Message-Id: <B4EB2F26-9D46-439A-9104-E7C940CCB83E@googlemail.com>
References: <2fd53c3a1002220300s293ee858r9400dfa4b07f9b3a@mail.gmail.com>
To: user@couchdb.apache.org

Hi Fabio,

this sounds "normal" to me, since couch views use btrees and (high) =
entropy hurts btree's update/insert performance.

greets
tisba

On 22.02.2010, at 12:00, Fabio Forno wrote:

> Hi,
> during view generation I've noticed that view re-indexing speed seems
> very related to the entropy of keys. For example I've map/reduce view
> which counts the a set of resources with a score and a type. The score
> has a very high entropy (few tens of resources for each score), while
> the resource type is limited (>100k per type). If I emit keys as
> [type, score] map/reduce computation seems much slower than [score,
> type]. Is it normal or a just a case? Isn't there the risk of
> degeneration if the numbers of resources grows too much (eg. millions
> per resource type)?
> Since I need to do range queries according the score, but only on
> selected types of resources, I think that the [type, score] key is
> preferable, however this degradation in speed concerns me. Any hint?
> thanks in advance.
>=20
> --=20
> Fabio Forno,
> Bluendo srl http://www.bluendo.com
> jabber id: ff@jabber.bluendo.com