build_relation

# File activerecord/lib/active_record/validations/uniqueness.rb, line 58
      def build_relation(klass, table, attribute, value) #:nodoc:
        if reflection = klass._reflect_on_association(attribute)
          attribute = reflection.foreign_key
          value = value.attributes[reflection.klass.primary_key] unless value.nil?
        end

        attribute_name = attribute.to_s

        # the attribute may be an aliased attribute
        if klass.attribute_aliases[attribute_name]
          attribute = klass.attribute_aliases[attribute_name]
          attribute_name = attribute.to_s
        end

        column = klass.columns_hash[attribute_name]
        value  = klass.connection.type_cast(value, column)
        if value.is_a?(String) && column.limit
          value = value.to_s[0, column.limit]
        end

        if !options[:case_sensitive] && value && column.text?
          # will use SQL LOWER function before comparison, unless it detects a case insensitive collation
          klass.connection.case_insensitive_comparison(table, attribute, column, value)
        else
          klass.connection.case_sensitive_comparison(table, attribute, column, value)
        end
      end