2 files changed, 17 insertions, 0 deletions
diff --git a/lib/arel/algebra/relations/operations/group.rb b/lib/arel/algebra/relations/operations/group.rb
index 68c626e917..af0d3c6808 100644
--- a/lib/arel/algebra/relations/operations/group.rb
+++ b/lib/arel/algebra/relations/operations/group.rb
@@ -14,5 +14,9 @@ module Arel
         @relation == other.relation &&
         @groupings == other.groupings
     end
+
+    def eval
+      raise NotImplementedError
+    end
   end
 end
diff --git a/lib/arel/algebra/relations/operations/join.rb b/lib/arel/algebra/relations/operations/join.rb
index 9eee84113a..5d19873f62 100644
--- a/lib/arel/algebra/relations/operations/join.rb
+++ b/lib/arel/algebra/relations/operations/join.rb
@@ -53,6 +53,19 @@ module Arel
 
     # FIXME remove this.  :'(
     alias :eql? :==
+
+    def eval
+      result = []
+      relation1.call.each do |row1|
+        relation2.call.each do |row2|
+          combined_row = row1.combine(row2, self)
+          if predicates.all? { |p| p.eval(combined_row) }
+            result << combined_row
+          end
+        end
+      end
+      result
+    end
   end
 
   class InnerJoin  < Join; end