Relation#from to accept other Relation objects

Record.from("(#{sub_query.to_sql})")    -> Record.from(sub_query)
Record.from("(#{sub_query.to_sql}) a")  -> Record.from(sub_query, :a)

2 files changed, 13 insertions, 1 deletions

diff --git a/activerecord/test/cases/relation_test.rb b/activerecord/test/cases/relation_test.rb
index 8a7a2441d4..89f818a689 100644
--- a/activerecord/test/cases/relation_test.rb
+++ b/activerecord/test/cases/relation_test.rb
@@ -203,13 +203,18 @@ module ActiveRecord
       assert_equal [], relation.extending_values
     end
 
-    (Relation::SINGLE_VALUE_METHODS - [:lock, :reordering, :reverse_order, :create_with]).each do |method|
+    (Relation::SINGLE_VALUE_METHODS - [:from, :lock, :reordering, :reverse_order, :create_with]).each do |method|
       test "##{method}!" do
         assert relation.public_send("#{method}!", :foo).equal?(relation)
         assert_equal :foo, relation.public_send("#{method}_value")
       end
     end
 
+    test '#from!' do
+      assert relation.from!('foo').equal?(relation)
+      assert_equal ['foo', nil], relation.from_value
+    end
+
     test '#lock!' do
       assert relation.lock!('foo').equal?(relation)
       assert_equal 'foo', relation.lock_value
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index 76b868c7b4..dee31f4772 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -133,6 +133,13 @@ class RelationTest < ActiveRecord::TestCase
     assert topics.loaded?
   end
 
+  def test_finiding_with_subquery
+    relation = Topic.where(:approved => true)
+    assert_equal relation.to_a, Topic.select('*').from(relation).to_a
+    assert_equal relation.to_a, Topic.select('subquery.*').from(relation).to_a
+    assert_equal relation.to_a, Topic.select('a.*').from(relation, :a).to_a
+  end
+
   def test_finding_with_conditions
     assert_equal ["David"], Author.where(:name => 'David').map(&:name)
     assert_equal ['Mary'],  Author.where(["name = ?", 'Mary']).map(&:name)