lib/veritas/algebra/join.rb in veritas-0.0.4 vs lib/veritas/algebra/join.rb in veritas-0.0.5

@@ -5,10 +5,17 @@
 
     # The join between relations
     class Join < Relation
       include Relation::Operation::Combination
 
+      # The common headers between the operands
+      #
+      # @return [Header]
+      #
+      # @api private
+      attr_reader :join_header
+
       # Instantiate a new Join
       #
       # @example
       #   join = Join.new(left, right)
       #
@@ -52,11 +59,11 @@
       # @api private
       def initialize(left, right)
         super
         right_header      = right.header
         @join_header      = left.header  & right_header
-        @remainder_header = right_header - @join_header
+        @remainder_header = right_header - join_header
       end
 
       # Iterate over each tuple in the set
       #
       # @example
@@ -71,12 +78,12 @@
       # @return [self]
       #
       # @api public
       def each(&block)
         return to_enum unless block_given?
-        index = build_index
         util  = Relation::Operation::Combination
+        index = build_index
 
         left.each do |left_tuple|
           right_tuples = index[join_tuple(left_tuple)]
           if right_tuples
             util.combine_tuples(header, left_tuple, right_tuples, &block)
@@ -107,11 +114,11 @@
       #
       # @return [Tuple]
       #
       # @api private
       def join_tuple(tuple)
-        tuple.project(@join_header)
+        tuple.project(join_header)
       end
 
       # Generate a tuple with the disjoint attributes to use in the join
       #
       # @return [Tuple]
@@ -130,10 +137,10 @@
         #
         # @example natural join
         #   join = relation.join(other)
         #
         # @example theta-join using a block
-        #   join = relation.join(other) { |r| r[:a].gte(r[:b]) }
+        #   join = relation.join(other) { |r| r.a.gte(r.b) }
         #
         # @param [Relation] other
         #   the other relation to join
         #
         # @yield [relation]