Restore support for Model.pluck('sql fragment')

2 files changed, 10 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index 3ce9995031..0044c49c1d 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -130,7 +130,8 @@ module ActiveRecord
       column = types[key]
 
       result.map do |attributes|
-        value = klass.initialize_attributes(attributes)[key]
+        raise ArgumentError, "Pluck expects to select just one attribute: #{attributes.inspect}" unless attributes.one?
+        value = klass.initialize_attributes(attributes).first[1]
         if column
           column.type_cast value
         else
diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index e096585f62..c9a70bae77 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -466,6 +466,14 @@ class CalculationsTest < ActiveRecord::TestCase
     assert_equal [7], Company.joins(:contracts).pluck(:developer_id)
   end
 
+  def test_pluck_with_selection_clause
+    assert_equal [50, 53, 55, 60], Account.pluck('DISTINCT credit_limit').sort
+  end
+
+  def test_pluck_expects_a_single_selection
+    assert_raise(ArgumentError) { Account.pluck 'id, credit_limit' }
+  end
+
   def test_plucks_with_ids
     assert_equal Company.all.map(&:id).sort, Company.ids.sort
   end