3 files changed, 20 insertions, 1 deletions
diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 5ff0d1e204..68a48e6431 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,5 +1,9 @@
 ## Rails 3.2.10 (unreleased)
 
+*   Fix `pluck` to work with joins. Backport of #4942.
+
+    *Carlos Antonio da Silva*
+
 *   Fix a problem with `translate_exception` method in a non English environment.
     Backport of #6397.
 
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index 45e9e64229..20c5fa03a2 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -177,7 +177,12 @@ module ActiveRecord
     #   Person.where(:confirmed => true).limit(5).pluck(:id)
     #
     def pluck(column_name)
-      column_name = column_name.to_s
+      if column_name.is_a?(Symbol) && column_names.include?(column_name.to_s)
+        column_name = "#{table_name}.#{column_name}"
+      else
+        column_name = column_name.to_s
+      end
+
       relation = clone
       relation.select_values = [column_name]
       klass.connection.select_all(relation.arel, nil, bind_values).map! do |attributes|
diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index 63383bded9..ab573d8cc8 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -493,4 +493,14 @@ class CalculationsTest < ActiveRecord::TestCase
     assert_equal [1,2,3,4], taks_relation.pluck(:id)
     assert_equal [false, true, true, true], taks_relation.pluck(:approved)
   end
+
+  def test_pluck_auto_table_name_prefix
+    c = Company.create!(:name => "test", :contracts => [Contract.new])
+    assert_equal [c.id], Company.joins(:contracts).pluck(:id)
+  end
+
+  def test_pluck_not_auto_table_name_prefix_if_column_joined
+    c = Company.create!(:name => "test", :contracts => [Contract.new(:developer_id => 7)])
+    assert_equal [7], Company.joins(:contracts).pluck(:developer_id).map(&:to_i)
+  end
 end