Add log message when loading records from Identity Map.

Signed-off-by: José Valim <jose.valim@gmail.com>

2 files changed, 17 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/identity_map.rb b/activerecord/lib/active_record/identity_map.rb
index d18b2b0a54..95a8e5cff7 100644
--- a/activerecord/lib/active_record/identity_map.rb
+++ b/activerecord/lib/active_record/identity_map.rb
@@ -50,7 +50,14 @@ module ActiveRecord
 
       def get(klass, primary_key)
         obj = repository[klass.symbolized_base_class][primary_key]
-        obj.is_a?(klass) ? obj : nil
+        if obj.is_a?(klass)
+          if ActiveRecord::Base.logger
+            ActiveRecord::Base.logger.debug "#{klass} with ID = #{primary_key} loaded from Identity Map"
+          end
+          obj
+        else
+          nil
+        end
       end
 
       def add(record)
diff --git a/activerecord/test/cases/identity_map_test.rb b/activerecord/test/cases/identity_map_test.rb
index 9cf3db7f87..199e59657d 100644
--- a/activerecord/test/cases/identity_map_test.rb
+++ b/activerecord/test/cases/identity_map_test.rb
@@ -388,6 +388,15 @@ class IdentityMapTest < ActiveRecord::TestCase
     assert_not_nil post.title
   end
 
+  def test_log
+    log = StringIO.new
+    ActiveRecord::Base.logger = Logger.new(log)
+    ActiveRecord::Base.logger.level = Logger::DEBUG
+    Post.find 1
+    Post.find 1
+    assert_match(/Post with ID = 1 loaded from Identity Map/, log.string)
+  end
+
 # Currently AR is not allowing changing primary key (see Persistence#update)
 # So we ignore it. If this changes, this test needs to be uncommented.
 #  def test_updating_of_pkey