Pluck should work with columns of the same name from different tables

The column name given by the adapter doesn't include the table
namespace, so going through the hashed version of the result set causes
overridden keys.

Fixes #15649

3 files changed, 15 insertions, 3 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 8e958a851e..e0a7552921 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,10 @@
+*   Pluck now works when selecting columns from different tables with the same
+    name.
+
+    Fixes #15649
+
+    *Sean Griffin*
+
 *   Remove `cache_attributes` and friends. All attributes are cached.
 
     *Sean Griffin*
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index 38970a66ae..028e4d80ab 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -176,9 +176,7 @@ module ActiveRecord
           }
         end
 
-        result = result.map do |attributes|
-          values = attributes.values
-
+        result = result.rows.map do |values|
           columns.zip(values).map { |column, value| column.type_cast_from_database value }
         end
         columns.one? ? result.map!(&:first) : result
diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index dfc6a7ec67..222b1505a8 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -610,4 +610,11 @@ class CalculationsTest < ActiveRecord::TestCase
     assert_equal [1,2,3,4,5], taks_relation.pluck(:id)
     assert_equal [false, true, true, true, true], taks_relation.pluck(:approved)
   end
+
+  def test_pluck_columns_with_same_name
+    expected = [["The First Topic", "The Second Topic of the day"], ["The Third Topic of the day", "The Fourth Topic of the day"]]
+    actual = Topic.joins(:replies)
+      .pluck('topics.title', 'replies_topics.title')
+    assert_equal expected, actual
+  end
 end