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From Adam Kocoloski <kocol...@apache.org>
Subject Re: couch sequence numbers and _all_docs_by_seq
Date Wed, 29 Apr 2009 13:55:48 GMT
On Apr 29, 2009, at 4:08 AM, eric casteleijn wrote:

> Paul Davis wrote:
>> Eric,
>> Implementation isn't a problem, but I would fear that replication
>> could screw views up. As in, your views would depend on the order of
>> document modification which could be impacted quite heavily by
>> replication etc.
>
> Ah right, hadn't thought of that. So in a system using replication,  
> views that would use the sequence number as a key would get a severe  
> performance penalty? (Just checking to see if I understand the  
> implications.) That might be a good enough reason not to expose this  
> as a feature, lest people start depending on it and saying CouchDb  
> is slow as a result.
>
> If this is true, I suppose it also holds for the built in  
> _all_docs_by_seq view?

I'm not sure Paul's comment is performance-related, actually.  I think  
he was more concerned that a view which incorporates update_seq could  
give different results on two servers that are using replication to  
stay synchronized with one another.  Paul, correct me if I'm  
misinterpreting you.

At the moment the replicator doesn't try to update documents on the  
target in the exact same order that they were updated on the source,  
but I think it could be done without too much of a penalty if we  
decided it was necessary.  Regards,

Adam

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