instance method raise_on_duplicate_column

# File activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb, line 605
        def raise_on_duplicate_column(name)
          if @columns_hash[name]
            if @columns_hash[name].primary_key?
              raise ArgumentError, "you can't redefine the primary key column '#{name}' on '#{@name}'. To define a custom primary key, pass { id: false } to create_table."
            else
              raise ArgumentError, "you can't define an already defined column '#{name}' on '#{@name}'."
            end
          end
        end