2 files changed, 19 insertions, 0 deletions
diff --git a/activerecord/test/cases/associations/join_model_test.rb b/activerecord/test/cases/associations/join_model_test.rb
index b83966e91c..f131dc01f6 100644
--- a/activerecord/test/cases/associations/join_model_test.rb
+++ b/activerecord/test/cases/associations/join_model_test.rb
@@ -44,6 +44,16 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
     assert !authors(:mary).unique_categorized_posts.loaded?
   end
 
+  def test_column_caching
+    # pre-heat our cache
+    Post.arel_table.columns
+    Comment.columns
+
+    Post.connection.column_calls = 0
+    2.times { Post.joins(:comments).to_a }
+    assert_equal 0, Post.connection.column_calls
+  end
+
   def test_has_many_uniq_through_find
     assert_equal 1, authors(:mary).unique_categorized_posts.find(:all).size
   end
diff --git a/activerecord/test/cases/helper.rb b/activerecord/test/cases/helper.rb
index 561bb22785..19a8a97c1a 100644
--- a/activerecord/test/cases/helper.rb
+++ b/activerecord/test/cases/helper.rb
@@ -57,6 +57,15 @@ ActiveRecord::Base.connection.class.class_eval do
   alias_method_chain :execute, :query_record
 end
 
+ActiveRecord::Base.connection.extend Module.new {
+  attr_accessor :column_calls
+  def columns(*args)
+    @column_calls += 1
+    super
+  end
+}
+ActiveRecord::Base.connection.column_calls = 0
+
 unless ENV['FIXTURE_DEBUG']
   module ActiveRecord::TestFixtures::ClassMethods
     def try_to_load_dependency_with_silence(*args)