Switch Arel::Relation to a module. This will allow for classes with Relation extended on them to represent relations themselves (as opposed to their instances being relations).

13 files changed, 22 insertions, 16 deletions

diff --git a/lib/arel/algebra/relations/operations/join.rb b/lib/arel/algebra/relations/operations/join.rb
index df457686cc..300cd31bcd 100644
--- a/lib/arel/algebra/relations/operations/join.rb
+++ b/lib/arel/algebra/relations/operations/join.rb
@@ -1,5 +1,7 @@
 module Arel
-  class Join < Relation
+  class Join
+    include Relation
+
     attributes :relation1, :relation2, :predicates
     deriving :==
     delegate :name, :to => :relation1
@@ -60,7 +62,7 @@ module Arel
     end
   end
 
-  class Relation
+  module Relation
     def join?
       false
     end
diff --git a/lib/arel/algebra/relations/relation.rb b/lib/arel/algebra/relations/relation.rb
index 51c622cbe8..1c1ded15c9 100644
--- a/lib/arel/algebra/relations/relation.rb
+++ b/lib/arel/algebra/relations/relation.rb
@@ -1,5 +1,5 @@
 module Arel
-  class Relation
+  module Relation
     attr_reader :count
 
     def session
diff --git a/lib/arel/algebra/relations/utilities/compound.rb b/lib/arel/algebra/relations/utilities/compound.rb
index 0734842b27..7039b82575 100644
--- a/lib/arel/algebra/relations/utilities/compound.rb
+++ b/lib/arel/algebra/relations/utilities/compound.rb
@@ -1,5 +1,7 @@
 module Arel
-  class Compound < Relation
+  class Compound
+    include Relation
+
     attr_reader :relation
     delegate :joins, :join?, :inserts, :taken, :skipped, :name, :externalizable?,
              :column_for, :engine, :sources, :locked, :table_alias,
diff --git a/lib/arel/algebra/relations/utilities/externalization.rb b/lib/arel/algebra/relations/utilities/externalization.rb
index 13758ccec9..795a3919f2 100644
--- a/lib/arel/algebra/relations/utilities/externalization.rb
+++ b/lib/arel/algebra/relations/utilities/externalization.rb
@@ -12,7 +12,7 @@ module Arel
     end
   end
 
-  class Relation
+  module Relation
     def externalize
       @externalized ||= externalizable?? Externalization.new(self) : self
     end
diff --git a/lib/arel/algebra/relations/utilities/nil.rb b/lib/arel/algebra/relations/utilities/nil.rb
index 6a9d678c45..04055d0ddb 100644
--- a/lib/arel/algebra/relations/utilities/nil.rb
+++ b/lib/arel/algebra/relations/utilities/nil.rb
@@ -1,7 +1,7 @@
 require 'singleton'
 
 module Arel
-  class Nil < Relation
-    include Singleton
+  class Nil
+    include Relation, Singleton
   end
 end
diff --git a/lib/arel/engines/memory/relations/array.rb b/lib/arel/engines/memory/relations/array.rb
index 577e327b19..6486dcbcc1 100644
--- a/lib/arel/engines/memory/relations/array.rb
+++ b/lib/arel/engines/memory/relations/array.rb
@@ -1,5 +1,7 @@
 module Arel
-  class Array < Relation
+  class Array
+    include Relation
+
     attributes :array,  :attribute_names_and_types
     include Recursion::BaseCase
     deriving :==, :initialize
diff --git a/lib/arel/engines/memory/relations/compound.rb b/lib/arel/engines/memory/relations/compound.rb
index 6dda92a6a1..0f3c24f9ec 100644
--- a/lib/arel/engines/memory/relations/compound.rb
+++ b/lib/arel/engines/memory/relations/compound.rb
@@ -1,5 +1,5 @@
 module Arel
-  class Compound < Relation
+  class Compound
     delegate :array, :to => :relation
 
     def unoperated_rows
diff --git a/lib/arel/engines/memory/relations/operations.rb b/lib/arel/engines/memory/relations/operations.rb
index a5082715a1..5d7b7670b6 100644
--- a/lib/arel/engines/memory/relations/operations.rb
+++ b/lib/arel/engines/memory/relations/operations.rb
@@ -50,7 +50,7 @@ module Arel
     end
   end
 
-  class Join < Relation
+  class Join
     def eval
       result = []
       relation1.call.each do |row1|
diff --git a/lib/arel/engines/sql/relations/operations/join.rb b/lib/arel/engines/sql/relations/operations/join.rb
index a3aaaa163b..7fad6400ad 100644
--- a/lib/arel/engines/sql/relations/operations/join.rb
+++ b/lib/arel/engines/sql/relations/operations/join.rb
@@ -1,5 +1,5 @@
 module Arel
-  class Join < Relation
+  class Join
     def table_sql(formatter = Sql::TableReference.new(self))
       relation1.externalize.table_sql(formatter)
     end
diff --git a/lib/arel/engines/sql/relations/relation.rb b/lib/arel/engines/sql/relations/relation.rb
index 5e8fc2e83e..f372589af1 100644
--- a/lib/arel/engines/sql/relations/relation.rb
+++ b/lib/arel/engines/sql/relations/relation.rb
@@ -1,5 +1,5 @@
 module Arel
-  class Relation
+  module Relation
     @@connection_tables_primary_keys = {}
 
     def compiler
diff --git a/lib/arel/engines/sql/relations/table.rb b/lib/arel/engines/sql/relations/table.rb
index aa70eaaa28..8ee7a94357 100644
--- a/lib/arel/engines/sql/relations/table.rb
+++ b/lib/arel/engines/sql/relations/table.rb
@@ -1,6 +1,6 @@
 module Arel
-  class Table < Relation
-    include Recursion::BaseCase
+  class Table
+    include Relation, Recursion::BaseCase
 
     cattr_accessor :engine, :tables
     attr_reader :name, :engine, :table_alias, :options
diff --git a/lib/arel/engines/sql/relations/utilities/compound.rb b/lib/arel/engines/sql/relations/utilities/compound.rb
index b8b0e7d269..55853be742 100644
--- a/lib/arel/engines/sql/relations/utilities/compound.rb
+++ b/lib/arel/engines/sql/relations/utilities/compound.rb
@@ -1,5 +1,5 @@
 module Arel
-  class Compound < Relation
+  class Compound
     delegate :table, :table_sql, :to => :relation
 
     def build_query(*parts)
diff --git a/lib/arel/engines/sql/relations/utilities/nil.rb b/lib/arel/engines/sql/relations/utilities/nil.rb
index 519ea8acf1..0f7ca5d757 100644
--- a/lib/arel/engines/sql/relations/utilities/nil.rb
+++ b/lib/arel/engines/sql/relations/utilities/nil.rb
@@ -1,5 +1,5 @@
 module Arel
-  class Nil < Relation
+  class Nil
     def table_sql(formatter = nil); '' end
     def name; '' end
   end