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From Damien Katz <dam...@apache.org>
Subject Re: couchdb transactions changes
Date Sun, 08 Feb 2009 14:38:00 GMT

On Feb 8, 2009, at 1:49 AM, Antony Blakey wrote:

>
> On 08/02/2009, at 5:05 PM, Damien Katz wrote:
>
>> In this case it has nothing to do with update transactions. MVCC is  
>> about each read operation having it's own snapshot of the database.
>
> Sure, but the MVCC snapshots are created by update transactions, yes?

Nope.

>
>
>> I'm stating that you must "read lock" the source database if you  
>> want this "consistent replication" thing you are trying to achieve.  
>> That's a fact.
>
> Sorry, I'm just trying to understand how replication, which sees an  
> MVCC snapshot, requires that I read-lock the source database.

Nope, each individual read operation gets a snapshot of the database.  
When you are replicating, there is one read operation for every  
document that must be sent. Each read request gives you a new MVCC  
database.

-Damien

>
>
> Antony Blakey
> --------------------------
> CTO, Linkuistics Pty Ltd
> Ph: 0438 840 787
>
> Success is not the key to happiness. Happiness is the key to success.
> -- Albert Schweitzer
>


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