Ensure `apply_join_dependency` for `collection_cache_key` if eager-loading is needed

Fixes #30315.

5 files changed, 17 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/collection_cache_key.rb b/activerecord/lib/active_record/collection_cache_key.rb
index f3e6516414..88b398ad45 100644
--- a/activerecord/lib/active_record/collection_cache_key.rb
+++ b/activerecord/lib/active_record/collection_cache_key.rb
@@ -12,6 +12,9 @@ module ActiveRecord
           timestamp = collection.max_by(&timestamp_column)._read_attribute(timestamp_column)
         end
       else
+        if collection.eager_loading?
+          collection = collection.send(:apply_join_dependency)
+        end
         column_type = type_for_attribute(timestamp_column.to_s)
         column = connection.column_name_from_arel_node(collection.arel_attribute(timestamp_column))
         select_values = "COUNT(*) AS #{connection.quote_column_name("size")}, MAX(%s) AS timestamp"
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index 116bddce85..11256ab3d9 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -130,7 +130,7 @@ module ActiveRecord
     #      end
     def calculate(operation, column_name)
       if has_include?(column_name)
-        relation = apply_join_dependency(construct_join_dependency)
+        relation = apply_join_dependency
         relation.distinct! if operation.to_s.downcase == "count"
 
         relation.calculate(operation, column_name)
@@ -180,7 +180,7 @@ module ActiveRecord
       end
 
       if has_include?(column_names.first)
-        relation = apply_join_dependency(construct_join_dependency)
+        relation = apply_join_dependency
         relation.pluck(*column_names)
       else
         relation = spawn
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index 707245bab2..18566b5662 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -394,7 +394,7 @@ module ActiveRecord
         )
       end
 
-      def apply_join_dependency(join_dependency)
+      def apply_join_dependency(join_dependency = construct_join_dependency)
         relation = except(:includes, :eager_load, :preload).joins!(join_dependency)
 
         if using_limitable_reflections?(join_dependency.reflections)
diff --git a/activerecord/test/cases/collection_cache_key_test.rb b/activerecord/test/cases/collection_cache_key_test.rb
index c137693211..19d6464a22 100644
--- a/activerecord/test/cases/collection_cache_key_test.rb
+++ b/activerecord/test/cases/collection_cache_key_test.rb
@@ -73,6 +73,16 @@ module ActiveRecord
       assert_equal last_developer_timestamp.to_s(ActiveRecord::Base.cache_timestamp_format), $3
     end
 
+    test "cache_key for relation with includes" do
+      comments = Comment.includes(:post).where("posts.type": "Post")
+      assert_match(/\Acomments\/query-(\h+)-(\d+)-(\d+)\z/, comments.cache_key)
+    end
+
+    test "cache_key for loaded relation with includes" do
+      comments = Comment.includes(:post).where("posts.type": "Post").load
+      assert_match(/\Acomments\/query-(\h+)-(\d+)-(\d+)\z/, comments.cache_key)
+    end
+
     test "it triggers at most one query" do
       developers = Developer.where(name: "David")
 
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index 8f872c38ba..a4505a4892 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -191,6 +191,7 @@ ActiveRecord::Schema.define do
     t.string :resource_id
     t.string :resource_type
     t.integer :developer_id
+    t.datetime :updated_at
     t.datetime :deleted_at
     t.integer :comments
   end