Ignore order when doing count.

This is necessary because Postgresql doesn't play nice with ORDER BY and
no GROUP BY.

Fixes #14621.

activerecord/lib/active_record/relation/calculations.rb

@@ -231,7 +231,7 @@ def operation_over_aggregate_column(column, operation, distinct)
 
     def execute_simple_calculation(operation, column_name, distinct) #:nodoc:
       # Postgresql doesn't like ORDER BY when there are no GROUP BY
-      relation = reorder(nil)
+      relation = unscope(:order)
 
       column_alias = column_name
 

activerecord/test/cases/calculations_test.rb

@@ -387,6 +387,20 @@ def test_count_with_too_many_parameters_raises
     assert_raise(ArgumentError) { Account.count(1, 2, 3) }
   end
 
+  def test_count_with_order
+    assert_equal 6, Account.order(:credit_limit).count
+  end
+
+  def test_count_with_reverse_order
+    assert_equal 6, Account.order(:credit_limit).reverse_order.count
+  end
+
+  def test_count_with_where_and_order
+    assert_equal 1, Account.where(firm_name: '37signals').count
+    assert_equal 1, Account.where(firm_name: '37signals').order(:firm_name).count
+    assert_equal 1, Account.where(firm_name: '37signals').order(:firm_name).reverse_order.count
+  end
+
   def test_should_sum_expression
     # Oracle adapter returns floating point value 636.0 after SUM
     if current_adapter?(:OracleAdapter)