After reading the doc for CouchDB::Client, the only thing I see that may be helpful is under "Internal Methods" (which has a note: "You will use these at your own risk" -- offering a technique to obtain Couch objects.

But, perhaps documents for the DB engine will provide some clues. Have you read those (with a microscope?)

Or, perhaps these results from a Google search (terms: "CouchDB rename document") will be helpful:

Storing Documents - CouchDB: The Definitive Guide
guide.couchdb.org/draft/documents.html
Documents are CouchDB's central data structure. To best understand and use CouchDB, you need to think in documents. This chapter walks you though the ...

CouchDB Document API - Apache Wiki
https://wiki.apache.org/couchdb/HTTP_Doc...
Apache Software Foundation
Jun 5, 2013 - A CouchDB document is simply a JSON object. You can use any JSON structure with nesting. You can fetch the document's revision ...

Document_Update_Handlers - Couchdb Wiki - Apache Wiki
https://wiki.apache.org/couchdb/Document...
Apache Software Foundation
Apr 23, 2014 - The official documentation has moved to http://docs.couchdb.org ... When the request to an update handler includes a document ID in the URL, ...

[CouchDB-user] rename document attachment - Grokbase
grokbase.com › Groups › CouchDB › user › September 2009
Sep 3, 2009 - (4 replies) I have a simple html/javascript app that uploads an attachment to a document. However, once it is uploaded I want to rename it to a ...