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From Sebastian Cohnen <sebastiancoh...@googlemail.com>
Subject Re: key entropy and view performance
Date Mon, 22 Feb 2010 12:24:10 GMT
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.
> 
> -- 
> Fabio Forno,
> Bluendo srl http://www.bluendo.com
> jabber id: ff@jabber.bluendo.com


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