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From Tim Parkin <i...@timparkin.co.uk>
Subject Re: Restricting user interactions to a single document -- was [VOTE] Apache CouchDB 0.9.0 release
Date Mon, 30 Mar 2009 11:08:31 GMT
Brian Candler wrote:
> On Fri, Mar 27, 2009 at 08:36:05PM +0000, Tim Parkin wrote:
>> Yes.. but we're not trying to guarantee consistency, just trying to
>> prevent inconsistency where possible
> 
> In that case, I'm afraid I don't really understand what the goals are. Do
> you want to be able to guarantee a rollback, or not? If you don't care about
> rollback always being successful, then you can just PUT back the old
> documents.
> 

Yes you are right.. we would like to be able to close the chance for
conflicts in a local database whilst dealing with conflicts caused by
replication.

We've come up with a few scenarios that limit the chance of conflicts
but the only scenario that removes it is atomic changes (as far as we
can tell - although because we're not sure we aren't saying we need
atomic changes , just that we need to close the chance for conflicts on
local changes).

Just replacing the documents leaves opportunity for someone else to grab
the documents before they are removed. We've tried using some form of
transactional change using markers but this is quite complicated and
still leaves a window of opportunity for *local* inconsistency.

We do want to guarantee a rollback, is there a way to do this without
atomic changes? If there isn't then, yes, we will probably need some
form of atomic change.


Tim

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