Add method call count instrumentation

app/models/concerns/routable.rb

@@ -59,12 +59,23 @@ module Routable
     def where_full_path_in(paths)
       return none if paths.empty?
+      increment_full_path_in_counter
+
       wheres = paths.map do |path|
         "(LOWER(routes.path) = LOWER(#{connection.quote(path)}))"
       end
       joins(:route).where(wheres.join(' OR '))
     end
+
+    # Temporary instrumentation of method calls for .where_full_path_in
+    def increment_full_path_in_counter
+      @counter ||= Gitlab::Metrics.counter(:routable_caseinsensitive_lookup_calls, 'Number of calls to Routable.where_full_path_in')
+
+      @counter.increment
+    rescue
+      # ignore the error
+    end
   end
   def full_name