Run query when using where(attr: []) and pluck with expression columns

Author: fatkodima

activerecord/lib/active_record/relation/calculations.rb

@@ -315,7 +315,7 @@ def pluck(*column_names)
         columns = relation.arel_columns(column_names)
         relation.select_values = columns
         result = skip_query_cache_if_necessary do
-          if where_clause.contradiction?
+          if where_clause.contradiction? && !possible_aggregation?(column_names)
             ActiveRecord::Result.empty(async: @async)
           else
             model.with_connection do |c|
@@ -450,6 +450,13 @@ def distinct_select?(column_name)
         column_name.is_a?(::String) && /\bDISTINCT[\s(]/i.match?(column_name)
       end
 
+      def possible_aggregation?(column_names)
+        column_names.any? do |column_name|
+          Arel.arel_node?(column_name) ||
+            (column_name.is_a?(String) && column_name.include?("("))
+        end
+      end
+
       def aggregate_column(column_name)
         case column_name
         when Arel::Expressions

activerecord/test/cases/relation_test.rb

@@ -445,6 +445,12 @@ def test_skip_preloading_after_arel_has_been_generated
       end
     end
 
+    test "runs queries when using pick with expression column and empty IN" do
+      assert_queries_count(1) do
+        assert_equal 0, Post.where(id: []).pick(Arel.sql("COUNT(*)"))
+      end
+    end
+
     test "can unscope empty IN" do
       assert_queries_count(1) do
         Post.where(id: []).unscope(where: :id).load