overwrite on update if _rev not latest?

[Michael Stillwell <mj...@beebo.org>]

Is there any way to get CouchDB to overwrite a document (instead of
generating a conflict) when updating an existing document with a _rev
that does not match the latest _rev?

One simple use case for this is that of a user opening up two user
profile tabs on a website, then editing both, and submitting both.
The second "update" will fail--is there a way to force this through?
(I don't particularly care if the second update clobbers some changes
from the first.)




Thanks,
Michael

-- 
http://beebo.org

Re: overwrite on update if _rev not latest?

[Michael Stillwell <mj...@beebo.org>]

On Wed, May 13, 2009 at 12:40 PM, Jan Lehnardt <ja...@apache.org> wrote:
>
> On 12 May 2009, at 09:28, Michael Stillwell wrote:
>
>> Is there any way to get CouchDB to overwrite a document (instead of
>> generating a conflict) when updating an existing document with a _rev
>> that does not match the latest _rev?
>>
>> One simple use case for this is that of a user opening up two user
>> profile tabs on a website, then editing both, and submitting both.
>> The second "update" will fail--is there a way to force this through?
>> (I don't particularly care if the second update clobbers some changes
>> from the first.)
>
> This goes against CouchDB's core design philosophy, so it is unlikely
> that we'll ever get this feature.
>
> I don't understand enough of you use case (how do "profiles" match
> documents et al). With a doc per profile, you don't get any write conflicts.

Can you explain further why a doc per profile would eliminate write
conflicts?  That's what I was assuming, and so I don't understand how
this helps.

If you need to know the latest revision of a document in order to
modify it, doesn't this make various common key-value use-cases
difficult to code?  (Essentially any situation where two or more tasks
write to the same key/document at around the same time, and you want
the most recent write to win.)

Another example of a problematic situation: a document represents
recent Flickr photos with a particular tag.  If two search tasks
(which query Flickr, then write the response back to couchdb) are
initiated simultaneously, the second save will fail.

I can only think of awkward loopy ways to code around this--is there
some elegant way?  (Also, why does couchdb work this way?  Most (all?)
other "new" key-value stores seem to overwrite previous values without
asking.)





Thanks,
Michael

-- 
http://beebo.org
+44 78 2118 9049

Re: overwrite on update if _rev not latest?

[Jan Lehnardt <ja...@apache.org>]

On 12 May 2009, at 09:28, Michael Stillwell wrote:

> Is there any way to get CouchDB to overwrite a document (instead of
> generating a conflict) when updating an existing document with a _rev
> that does not match the latest _rev?
>
> One simple use case for this is that of a user opening up two user
> profile tabs on a website, then editing both, and submitting both.
> The second "update" will fail--is there a way to force this through?
> (I don't particularly care if the second update clobbers some changes
> from the first.)

This goes against CouchDB's core design philosophy, so it is unlikely
that we'll ever get this feature.

I don't understand enough of you use case (how do "profiles" match
documents et al). With a doc per profile, you don't get any write  
conflicts.

Cheers
Jan
--