From 49a8c7bd5168ca84897166527f5c0d90126dc402 Mon Sep 17 00:00:00 2001
From: Emilio Tagua <miloops@gmail.com>
Date: Sun, 27 Dec 2009 16:38:32 -0300
Subject: Added "from" method, allowing to specify custom from clauses.

---
 lib/arel/algebra/relations.rb                    | 1 +
 lib/arel/algebra/relations/operations/from.rb    | 6 ++++++
 lib/arel/algebra/relations/relation.rb           | 3 ++-
 lib/arel/algebra/relations/utilities/compound.rb | 2 +-
 4 files changed, 10 insertions(+), 2 deletions(-)
 create mode 100644 lib/arel/algebra/relations/operations/from.rb

(limited to 'lib/arel/algebra')

diff --git a/lib/arel/algebra/relations.rb b/lib/arel/algebra/relations.rb
index f9fa24ba25..cee308299b 100644
--- a/lib/arel/algebra/relations.rb
+++ b/lib/arel/algebra/relations.rb
@@ -5,6 +5,7 @@ require 'arel/algebra/relations/utilities/externalization'
 require 'arel/algebra/relations/row'
 require 'arel/algebra/relations/writes'
 require 'arel/algebra/relations/operations/alias'
+require 'arel/algebra/relations/operations/from'
 require 'arel/algebra/relations/operations/group'
 require 'arel/algebra/relations/operations/join'
 require 'arel/algebra/relations/operations/order'
diff --git a/lib/arel/algebra/relations/operations/from.rb b/lib/arel/algebra/relations/operations/from.rb
new file mode 100644
index 0000000000..6bfd68dfc9
--- /dev/null
+++ b/lib/arel/algebra/relations/operations/from.rb
@@ -0,0 +1,6 @@
+module Arel
+  class From < Compound
+    attributes :relation, :sources
+    deriving :initialize, :==
+  end
+end
diff --git a/lib/arel/algebra/relations/relation.rb b/lib/arel/algebra/relations/relation.rb
index 5403e40fae..2ce3fdcce8 100644
--- a/lib/arel/algebra/relations/relation.rb
+++ b/lib/arel/algebra/relations/relation.rb
@@ -43,7 +43,7 @@ module Arel
         join(other_relation, OuterJoin)
       end
 
-      [:where, :project, :order, :take, :skip, :group].each do |operation_name|
+      [:where, :project, :order, :take, :skip, :group, :from].each do |operation_name|
         class_eval <<-OPERATION, __FILE__, __LINE__
           def #{operation_name}(*arguments, &block)
             arguments.all?(&:blank?) && !block_given?? self : #{operation_name.to_s.classify}.new(self, *arguments, &block)
@@ -130,6 +130,7 @@ module Arel
       def joins(formatter = nil); nil end # FIXME
       def taken;                  nil end
       def skipped;                nil end
+      def sources;                []  end
     end
     include DefaultOperations
   end
diff --git a/lib/arel/algebra/relations/utilities/compound.rb b/lib/arel/algebra/relations/utilities/compound.rb
index 5e775618f1..06bfce4ac0 100644
--- a/lib/arel/algebra/relations/utilities/compound.rb
+++ b/lib/arel/algebra/relations/utilities/compound.rb
@@ -2,7 +2,7 @@ module Arel
   class Compound < Relation
     attr_reader :relation
     delegate :joins, :join?, :inserts, :taken, :skipped, :name, :externalizable?,
-             :column_for, :engine,
+             :column_for, :engine, :sources,
              :to => :relation
 
     [:attributes, :wheres, :groupings, :orders].each do |operation_name|
-- 
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