most in memory operations save join and group

Conflicts:

	lib/arel/algebra/extensions/object.rb
	lib/arel/algebra/primitives/value.rb
	lib/arel/engines/memory/relations.rb
	lib/arel/engines/sql/formatters.rb
	lib/arel/engines/sql/primitives.rb
	spec/arel/unit/relations/alias_spec.rb
	spec/arel/unit/relations/array_spec.rb
	spec/arel/unit/relations/order_spec.rb

4 files changed, 53 insertions, 0 deletions

diff --git a/lib/arel/engines/memory/primitives.rb b/lib/arel/engines/memory/primitives.rb
index 77d4c1a52c..f8bbcedb55 100644
--- a/lib/arel/engines/memory/primitives.rb
+++ b/lib/arel/engines/memory/primitives.rb
@@ -10,4 +10,18 @@ module Arel
       value
     end
   end
+  
+  class Ordering
+    def eval(row1, row2)
+      (attribute.eval(row1) <=> attribute.eval(row2)) * direction
+    end
+  end
+  
+  class Descending < Ordering
+    def direction; -1 end
+  end
+  
+  class Ascending < Ordering
+    def direction; 1 end
+  end
 end
\ No newline at end of file
diff --git a/lib/arel/engines/memory/relations.rb b/lib/arel/engines/memory/relations.rb
index 9f8264c439..1b009537b9 100644
--- a/lib/arel/engines/memory/relations.rb
+++ b/lib/arel/engines/memory/relations.rb
@@ -1,3 +1,4 @@
 require 'arel/engines/memory/relations/array'
 require 'arel/engines/memory/relations/operations'
+require 'arel/engines/memory/relations/compound'
 
diff --git a/lib/arel/engines/memory/relations/compound.rb b/lib/arel/engines/memory/relations/compound.rb
new file mode 100644
index 0000000000..b029082d57
--- /dev/null
+++ b/lib/arel/engines/memory/relations/compound.rb
@@ -0,0 +1,5 @@
+module Arel
+  class Compound < Relation
+    delegate :array, :to => :relation
+  end
+end
diff --git a/lib/arel/engines/memory/relations/operations.rb b/lib/arel/engines/memory/relations/operations.rb
index eb11fb55fd..115df054df 100644
--- a/lib/arel/engines/memory/relations/operations.rb
+++ b/lib/arel/engines/memory/relations/operations.rb
@@ -4,4 +4,37 @@ module Arel
       relation.eval.select { |row| predicate.eval(row) }
     end
   end
+  
+  class Order < Compound
+    def eval
+      relation.eval.sort do |row1, row2|
+        ordering = orderings.detect { |o| o.eval(row1, row2) != 0 } || orderings.last
+        ordering.eval(row1, row2)
+      end
+    end
+  end
+  
+  class Project < Compound
+    def eval
+      relation.eval.collect { |r| r.slice(*projections) }
+    end
+  end
+  
+  class Take < Compound
+    def eval
+      relation.eval[0, taken]
+    end
+  end
+  
+  class Skip < Compound
+    def eval
+      relation.eval[skipped..-1]
+    end
+  end
+  
+  class Group < Compound
+    def eval
+      raise NotImplementedError
+    end
+  end
 end
\ No newline at end of file