using a legacy table with a column named 'type'

I have a legacy database I use to pull data from and one of the tables has a column named 'type'.

This cause the following sql to be generated (which doesn't work):

SELECT * FROM technical_hint WHERE ( (technical_hint.`type` = 'TechnicalHint' ) )

If I change the name of the column in the legacy db form 'type' to typex'. It works fine and this is what the query looks like:

SELECT * FROM technical_hint

Anybody know waht's happening and how I can get AR to consider this a 'non-magic' name?

Thanks

I have a legacy database I use to pull data from and one of the
tables has a column named 'type'.

This cause the following sql to be generated (which doesn't work):

SELECT * FROM technical_hint WHERE ( (technical_hint.`type` =
'TechnicalHint' ) )

If I change the name of the column in the legacy db form 'type' to
typex'. It works fine and this is what the query looks like:

SELECT * FROM technical_hint

Anybody know waht's happening and how I can get AR to consider this a
'non-magic' name?

You want the 'inheritance_column'. There's an AR method 'set_inheritance_column' that you can change it to something else.

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