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From J Chris Anderson <>
Subject Re: View Efficency
Date Tue, 29 Jun 2010 18:57:29 GMT

On Jun 29, 2010, at 11:01 AM, Behrad Zari wrote:

>> However, I think the original question from
>> Behrad still stands, is it more efficient to emit multiple keys per
>> document, or create multiple views?
> My own analysis was: when emting multiple keys per document, we have more index 
> keys, i.e. a bigger tree. Call it M*N indexes where M is number of emits per 
> document and N is number of docs emitted! Since querying a B+ tree is logaritmic 
> to the number of indexes, we MAY compare Log(N) with Log(M*N) with base of tree 
> block sizes! and Since M is not that big in real applications, I don't think 
> emiting multiple keys per doc will give much more poor performance in quering 
> the view in comparision to one emit per document. Take that In the later 
> scenario we may want to call multiple views and merge the results!
> Another unclarified thing for me is the situation where we emit array keys (i.e. 
> [key1, key2,...] ). I don't know about how that affects query time. Is the couch 
> behavior like single value keys?

yes it's not any different, except for the runtime of the collation algorithm, which should
not make much difference.


> I don't know about CouchDB implementation specifics such as determining block 
> size,... So I'd like CouchDB men can clarify these situations.
> --Behrad

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