On Tue, Aug 16, 2011 at 9:26 PM, Adam Kocoloski <kocolosk@apache.org> wrote:
> One of the principal uses of the replicator is to "make this database look like that one".  We're unable to do that in the general case today because of the combination of validation functions and out-of-order document transfers.  It's entirely possible for a document to be saved in the source DB prior to the installation of a ddoc containing a validation function that would have rejected the document, for the replicator to install the ddoc in the target DB before replicating the other document, and for the other document to then be rejected by the target DB.

Somebody asked about this on Stack Overflow. It was a very simple but
challenging question, but now I can't find it. Basically, he made your
point above.

Aren't you identifying two problems, though?

1. Sometimes you need to ignore validation to just make a nice, clean copy.
2. Replication batches (an optimization) are disobeying the change
sequence, which can screw up the replica.

I responded to #1 already.

But my feeling about #2 is that the optimization goes too far.
replication batches should always have boundaries immediately before
and after design documents. In other words, batch all you want, but
design documents [1] must always be in a batch size of 1. That will
retain the semantics.

[1] Actually, the only ddocs needing their own private batches are
those with a validate_doc_update field.

-- 
Iris Couch