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From "Markus Jelsma" <mar...@buyways.nl>
Subject Re: Rename a database?
Date Wed, 24 Feb 2010 01:10:48 GMT
I forgot to mention that readers of the old database will fail after
restart, the old file descriptor is obviously gone. You could probably
come up with this yourself however.

Again, please don't blaim me for any trouble ;-)


Markus Jelsma said:
> Size does matter and it is certainly not just bound only by the speed of
> the harddrive.
>
> I've just created a 0.9GB database with about 300.000 documents. It
> takes quite a while for it to replicate locally, it took 3m20s while
> copying a 2GB file takes less than 30s (on the same disk). CouchDB, of
> course, does a lot of work for replication such as reading, checking for
> conflicts and appending. A 12GB file will certainly take a long time on
> a system like this machine although it has lots of RAM, fast CPU and
> relatively fast disks.
>
> There is, however, a trick you might consider. But you may be asking for
> trouble on this one, so be careful.
>
> On Unix you can simply move (rename) a file while the readers are
> unaffected. Since CouchDB keeps the files open there _shouldn't_ be a
> problem. But keep in mind, writes to the old file (db name) will not
> show up in the newly move file, it will also not trigger an error
> (tested and confirmed here with a 10MB database).
>
> I am not sure why writes fail but don't trigger an error, perhaps i
> haven't given it enough though at this moment.
>
> Please, don't execute the things above without verification. Test it
> yourself with a reasonable comparable database and hopefully get some
> additional feedback in this method from CouchDB developers.
>
> Although i have executed this (even multiple times) in this test set up,
> and verified it works without a single problem, it doesn't proof it's
> actually a good practice.
>
>
>
> Sean Hess said:
>> The databases total to about 12 GB before any views are generated. How
>> long would it take to replicate that if it was local? Would it be
>> bound only by the harddrive speed?
>>
>> On Feb 23, 2010, at 4:07 PM, Nils Breunese <N.Breunese@vpro.nl> wrote:
>>
>>> In my experience replication is nearly instantaneous, especially
>>> since in this case it's to the local machine. But I don't know how
>>> large your databases are.
>>>
>>> You could even run the import on another machine and replicate the
>>> resulting database to the production machine afterwards to offload
>>> the production server from the import load. You could even replicate
>>> it to a separate database the production machine afterwards and the
>>> replicate to the 'real' live database if the difference in downtime
>>> due to network latency is significant enough.
>>>
>>> Nils.
>>> ________________________________________
>>> Van: Sean Hess [seanhess@gmail.com]
>>> Verzonden: dinsdag 23 februari 2010 23:49
>>> Aan: user@couchdb.apache.org
>>> Onderwerp: Re: Rename a database?
>>>
>>> I need the system to stay live the whole time, so the rename has to
>>> be nearly instantaneous. I do wish there was an http way to do it
>>> though.
>>>
>>> De informatie vervat in deze  e-mail en meegezonden bijlagen is
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