To add a slight variation on your potential solution… Instead of using a user defined predicate as the index namespace (in this case, team_messages), would it work to have a standard concept of “Namespace” in dgraph that would subidivide indexes? So your index definition would then be:
Namespace: team1 > message_value: string @index(fulltext) .
I am also trying to work out how to use dgraph for multi-tenant applications, and need to find a foolproof security solution that provides as many reasonable guarantees as possible that tenants will never be able to access each others’ data. I wonder if this namespace concept could also be means of subdividing the graph for access control per Possible timeline of implementing ACL's in Dgraph and Adding security to dgraph - #2 by mrjn.