ActiveRecord doesn't even support constraints in the first place.

pjungwir · on May 13, 2013

Shameless plug: here is a gem I wrote to manage foreign keys and CHECK constraints (and also indexes) in a Rails project:

https://github.com/pjungwir/db_leftovers

joevandyk · on May 13, 2013

What do you mean by "support constraints"?

If I, for example, violate a unique index, a ActiveRecord::RecordNotUnique exception is raised.

mjhoy · on May 13, 2013

Is that true? I might be wrong about this, but I think ActiveRecord checks for uniqueness (and other constraints) in application code, generating an extra database query if needed. If you _actually_ violate the unique index, a PGError is raised (if using postgres).

FooBarWidget · on May 13, 2013

No. ActiveRecord checks for constraints on top of what the database offers. You are free to specify database constraints if you like. In older versions of ActiveRecord, uniqueness errors generate a generic database exception. In recent versions, uniqueness errors generate the specific exception RecordNotUnique.