Thanks Phillip,
I was able to do that in my model class for the legacy table with this statement:
self.inheritance_column = "type_id"
there is no column named "type_id" in my legacy table and because of this AR doesn't try any Single Table Inheritance magic when I access it.
For anybody interested I keep the models I use for connecting to a legacy database in a folder in app/models and the models in that folder use an abstract connection model for communications with the legacy database.
Assuming database.yml has a setting for connecting to a database called: 'legacy_db' here's how I'd implement a model for using the table 'technical_hint' in the legacy database". The legacy technical_hint table also has many technical_hint_implementations and the example below shows how I create the association.
file app/models/legacy/connection_model.rb:
class Legacy::ConnectionModel < ActiveRecord::Base
def self.connection_possible?
begin
find(:first)
true
rescue SystemCallError, SocketError
false
end
end
establish_connection :legacy_db
end
file: app/models/legacy/technical_hint.rb:
class Legacy::TechnicalHint < Legacy::ConnectionModel
set_table_name "technical_hint"
set_primary_key "technical_hint_id"
has_many :technical_hint_implementations,
:class_name => "Teemss2::TechnicalHintImplementation",
:foreign_key => "technical_hint_id"
self.inheritance_column = "type_id"
end
In the example above the technical_hint table also has a 'type' column which I need to tell AR to ignore by telling AR to use a non-existent column name for the the column it uses to do Single Table Inheritance magic.
This model is referenced like this in an application.
hints = Legacy::TechnicalHint.find(:all);
Implementing the models this way allows me to:
1) keep all the implementation details about a legacy database well scoped.
2) lets me create first classRrails TechnicalHint model in my application which won't conflict with the model from the legacy table.
for which I am only using the legacy model