fixes different `count` calculation when using `size` manual `select` with DISTINCT

When using `select` with `'DISTINCT( ... )'` if you use method `size` on a non loaded relation it overrides the column selected by passing `:all` so it returns different value than count.

This fixes #35214

1 files changed, 8 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index bdd3c540bb..4f9ddf302e 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -221,7 +221,6 @@ module ActiveRecord
     end
 
     private
-
       def has_include?(column_name)
         eager_loading? || (includes_values.present? && column_name && column_name != :all)
       end
@@ -236,10 +235,12 @@ module ActiveRecord
         if operation == "count"
           column_name ||= select_for_count
           if column_name == :all
-            if distinct && (group_values.any? || select_values.empty? && order_values.empty?)
+            if !distinct
+              distinct = distinct_select?(select_for_count) if group_values.empty?
+            elsif group_values.any? || select_values.empty? && order_values.empty?
               column_name = primary_key
             end
-          elsif column_name.is_a?(::String) && /\bDISTINCT[\s(]/i.match?(column_name)
+          elsif distinct_select?(column_name)
             distinct = nil
           end
         end
@@ -251,6 +252,10 @@ module ActiveRecord
         end
       end
 
+      def distinct_select?(column_name)
+        column_name.is_a?(::String) && /\bDISTINCT[\s(]/i.match?(column_name)
+      end
+
       def aggregate_column(column_name)
         return column_name if Arel::Expressions === column_name