On Nov 1, 2009, at 5:07 PM, Brian Candler wrote:
At http://wiki.apache.org/couchdb/HTTP_Bulk_Document_API I see the
following:
"Bulk updates work independently of replication, meaning document
revisions
originally saved as part of an all or nothing transaction will be
replicated
individually, not as part of a bulk transaction. This means other
replica
instances may only have a subset of the transaction, and if an
update is
rejected by the remote node during replication (e.g. not authorized
error)
the remote node may never have the complete transaction."
I had a vague idea from the original discussions that these
transactions
would remain together, but this appears to be wrong.
I'd just like to ask if the lack of boundaries for replication is
intentional behaviour, or just an artefact of the current
implementation
which might change?
It's intentional behavior. Documents are meant to be independent, even
conflicts..
I can think of circumstances where it might be useful to keep them
together.
Consider, for example, an all_or_nothing transaction which is used to
resolve a conflict between three documents: it does this by writing
a new
revision, and deleting the other two revisions.
If this set of updates became split upon replication, it might end up
deleting the two old revisions but not updating the other document;
thus you
would have lost data from those two revisions.
Any thoughts or comments?
Yes, you can make a situation where somehow a user has legal updates
to certain conflicts, but not others, on a particular node A. On some
other node B, somehow the security was different and he was allowed to
update all the docs. Then an attempt to merge all the conflicts into
the document the user didn't really have edit access too will not be
replicated from node B to node A.
It's a contrived situation, but possible with misconfigured or updated
security settings that haven't propagated.
However, if you doing this as a VCS where you keep all the diffs, then
simply put the edit history as diffs into even the deleted documents.
Deleted docs actually can have a body and attachments, for just this
reason. Then no data is lost even when weird security settings
disallow only certain replicated edits.
-Damien
Regards,
Brian.
