move query limit to base event fetcher

lib/gitlab/cycle_analytics/base_event_fetcher.rb

@@ -5,6 +5,8 @@ module Gitlab
 
       attr_reader :projections, :query, :stage, :order
 
+      MAX_EVENTS = 50
+
       def initialize(project:, stage:, options:)
         @project = project
         @stage = stage
@@ -38,7 +40,7 @@ module Gitlab
       def events_query
         diff_fn = subtract_datetimes_diff(base_query, @options[:start_time_attrs], @options[:end_time_attrs])
 
-        base_query.project(extract_diff_epoch(diff_fn).as('total_time'), *projections).order(order.desc)
+        base_query.project(extract_diff_epoch(diff_fn).as('total_time'), *projections).order(order.desc).take(MAX_EVENTS)
       end
 
       def default_order