Merge pull request #26981 from kamipo/should_not_except_order_for_exists

Should except `:distinct` rather than `:order` for `exists?`

activerecord/CHANGELOG.md

@@ -14,7 +14,8 @@
 
     *Pavel Evstigneev*
 
-*   Avoid `unscope(:order)` when `limit_value` is presented for `count`.
+*   Avoid `unscope(:order)` when `limit_value` is presented for `count`
+    and `exists?`.
 
     If `limit_value` is presented, records fetching order is very important
     for performance. We should not unscope the order in the case.

activerecord/lib/active_record/relation/finder_methods.rb

@@ -321,7 +321,7 @@ def exists?(conditions = :none)
       relation = apply_join_dependency(self, construct_join_dependency(eager_loading: false))
       return false if ActiveRecord::NullRelation === relation
 
-      relation = relation.except(:select, :order).select(ONE_AS_ONE).limit(1)
+      relation = relation.except(:select, :distinct).select(ONE_AS_ONE).limit(1)
 
       case conditions
       when Array, Hash