find_left_table_pk

# File activerecord/lib/arel/visitors/mssql.rb, line 140
        def find_left_table_pk(o)
          if o.kind_of?(Arel::Nodes::Join)
            find_left_table_pk(o.left)
          elsif o.instance_of?(Arel::Table)
            find_primary_key(o)
          end
        end