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From Jason Smith <...@iriscouch.com>
Subject Re: Unique instance IDs?
Date Tue, 13 Dec 2011 01:25:11 GMT
On Tue, Dec 13, 2011 at 8:03 AM, Paul Davis <paul.joseph.davis@gmail.com> wrote:
> Having a UUID for every database created is the ideal
> harmonious-to-theory manifestation of "what is a db?" but we have to
> deal with reality when people may copy a file which makes things a bit
> weird when there are two instances of a UUID db.

You didn't say "harsh reality," but to list some legitimate situations
where people might copy .couch files:

* Restoring from backups
* Cloning a VMWare image
* Booting an EC2 AMI
* NAS storage clusters
* Couchbase mobile bootstrapping

>> There's actually no problem with moving DBs around today, except that
>> replication starts over (unless you change host names to match).
>
> The "except that replication starts over" is a very significant caveat
> that I would say contradicts the entire "no problem" description.

Nobody has shown that "replication starts over" is bad. The implicit
assumption is that starting over is costly. At present, yes, that is
true, but that's mostly a bunch of "no-op" round-trips diffing the
revs.

If there were a hypothetical single query which let the receiver
assess its exact relationship to an arbitrary sender's data, I don't
think "starts over" would sound as awful.

-- 
Iris Couch

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