Using Rails with existing database

Question

So I have an existing postgres database which gets populated by a python script. Now I am making a rails api which serves that data to a client. To my amusement all that I had to do is to create model classes and simply define relationships. No migration files, no schema, it just works. So a couple of questions.

• Am I right in saying that schema.rb is only needed for creating the database? If I am not running any migrations in my rails app I don't need any schema or migration files at all?
• I used to think that rails infers the names of model methods with the help of schema.rb . But it seems the only glue that ties ORM layer and the database is naming conventions? Are there any pitfalls I might be overlooking in doing things this way?

Answer 1

schema.rb is indeed not required by ActiveRecord.

It is used for:

• having a quick overview of the state of the database
• creating thedatabase tables when using db:schema:load task
• in gems like Apartment, (I think) it is used to create tenant specific schemas

TL:DR; - you don't really need schema.rb file but it's always good to have it as an authoritative source of db information.

More info here: http://edgeguides.rubyonrails.org/active_record_migrations.html#schema-dumping-and-you