Hi, since very early versions CouchDB view functions are able to emit(key,{_id:other_doc_id}), which, being requested with ?include_docs=true, resolves into external doc. CouchDB docs titled the feature "Joins with views", https://docs.couchdb.org/en/stable/ddocs/views/joins.html.
Also since 2.2 Couch can process multiple view index queries in a single request. I wonder if CouchDB could somewhat cross-wire both mechanics. Like replacing .value for emit(key,{_rows:[other_view_keys]}) entries when say ?expand_rows=true requested. Or keeping .value intact, but add .rows:[other_rows] property. Or even make it recursive N level deep with expand_rows=N, with N=1 for true. Any thoughts? ermouth