Add :row_count in cached sql.active_record payload

Previously we added :row_count to the instrumentation payload for
sql.active_record, but only for uncached queries. This adds the same
information on queries which are cached.

Author: jhawthorn

activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb

@@ -266,7 +266,7 @@ def lookup_sql_cache(sql, name, binds)
           if result
             ActiveSupport::Notifications.instrument(
               "sql.active_record",
-              cache_notification_info(sql, name, binds)
+              cache_notification_info_result(sql, name, binds, result)
             )
           end
 
@@ -288,13 +288,19 @@ def cache_sql(sql, name, binds)
           if hit
             ActiveSupport::Notifications.instrument(
               "sql.active_record",
-              cache_notification_info(sql, name, binds)
+              cache_notification_info_result(sql, name, binds, result)
             )
           end
 
           result.dup
         end
 
+        def cache_notification_info_result(sql, name, binds, result)
+          payload = cache_notification_info(sql, name, binds)
+          payload[:row_count] = result.length
+          payload
+        end
+
         # Database adapters can override this method to
         # provide custom cache information.
         def cache_notification_info(sql, name, binds)

activerecord/test/cases/instrumentation_test.rb

@@ -149,6 +149,29 @@ def test_payload_row_count_on_raw_sql
       ActiveSupport::Notifications.unsubscribe(subscriber) if subscriber
     end
 
+    def test_payload_row_count_on_cache
+      events = []
+      callback = -> (event) do
+        payload = event.payload
+        events << payload if payload[:sql].include?("SELECT")
+      end
+
+      Book.create!(name: "row count book")
+      ActiveSupport::Notifications.subscribed(callback, "sql.active_record") do
+        Book.cache do
+          Book.first
+          Book.first
+        end
+      end
+
+      assert_equal 2, events.size
+      assert_not events[0][:cached]
+      assert events[1][:cached]
+
+      assert_equal 1, events[0][:row_count]
+      assert_equal 1, events[1][:row_count]
+    end
+
     def test_payload_connection_with_query_cache_disabled
       connection = ClothingItem.lease_connection
       subscriber = ActiveSupport::Notifications.subscribe("sql.active_record") do |_, _, _, _, payload|