Add events counter cop

lib/gitlab/usage_data.rb

@@ -406,13 +406,8 @@ module Gitlab
 
       # rubocop: disable CodeReuse/ActiveRecord
       def merge_requests_users(time_period)
-        query =
-          Event
-            .where(target_type: Event::TARGET_TYPES[:merge_request].to_s)
-            .where(time_period)
-
         distinct_count(
-          query,
+          Event.where(target_type: Event::TARGET_TYPES[:merge_request].to_s).where(time_period),
           :author_id,
           start: user_minimum_id,
           finish: user_maximum_id

rubocop/cop/usage_data/event_counters.rb

+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Gitlab
+      class EventCounters < RuboCop::Cop::Cop
+        MSG = 'Use the `count` or `distinct_count`'
+
+        def_node_matcher :events_table, <<~PATTERN
+          $(send (const {nil cbase} :Event ) ...)
+        PATTERN
+
+        def on_send(node)
+          return unless usage_data_files?(node)
+
+          matched_node = events_table(node)
+
+          return if matched_node.nil?
+
+          method_name = matched_node.parent.children[1]
+
+          add_offense(node, location: :expression) unless [:count, :distinct_count].include?(method_name)
+        end
+
+        private
+
+        def usage_data_files?(node)
+          path = node.location.expression.source_buffer.name
+          path.include?('usage_data.rb')
+        end
+      end
+    end
+  end
+end