Merge pull request #34013 from bogdan/relation-merge-from

Bugfix ActiveRecord::Relation#merge special case of from clause

1 files changed, 6 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/relation/merger.rb b/activerecord/lib/active_record/relation/merger.rb
index 07b16a0740..4de7465128 100644
--- a/activerecord/lib/active_record/relation/merger.rb
+++ b/activerecord/lib/active_record/relation/merger.rb
@@ -171,9 +171,7 @@ module ActiveRecord
         end
 
         def merge_clauses
-          if relation.from_clause.empty? && !other.from_clause.empty?
-            relation.from_clause = other.from_clause
-          end
+          relation.from_clause = other.from_clause if replace_from_clause?
 
           where_clause = relation.where_clause.merge(other.where_clause)
           relation.where_clause = where_clause unless where_clause.empty?
@@ -181,6 +179,11 @@ module ActiveRecord
           having_clause = relation.having_clause.merge(other.having_clause)
           relation.having_clause = having_clause unless having_clause.empty?
         end
+
+        def replace_from_clause?
+          relation.from_clause.empty? && !other.from_clause.empty? &&
+            relation.klass.base_class == other.klass.base_class
+        end
     end
   end
 end