I have a situation where I have two models, companies and permissions, where companies is in a separate database from my permissions database. This is a has and belongs to many relationship because each company can have many permissions and each permission can belong to many companies.
The reason the two databases are split is because the company database runs a high demand production application and the permissions database controls the permissions for another application.
With rails, it looks for the join table in the same database as the primary table. For instance, if I do company.permissions, it looks in the company database for company_permissions. If I do permission.companies it looks in the permissions database.
What is the best solution to using a has and belongs to many relationship with multiple databases?
Has and belongs to many is old, clunky, and problematic. I recommend using has_many instead. You can specify the relationship table with the ‘:through’ option; just pick which database you want it to reside in and create a model to represent it. http://apidock.com/rails/ActiveRecord/Associations/ClassMethods/has_many