PERF: correctly index event dates (#34877)

plugins/discourse-calendar/app/models/discourse_post_event/event_date.rb

@@ -69,6 +69,7 @@ end
 # Indexes
 #
 #  idx_discourse_calendar_post_event_dates_event_id_starts_at_uniq  (event_id,starts_at) UNIQUE
+#  index_discourse_calendar_post_event_dates_on_event_id_and_dates  (event_id,finished_at DESC,starts_at DESC)
 #  index_discourse_calendar_post_event_dates_on_event_id            (event_id)
 #  index_discourse_calendar_post_event_dates_on_finished_at         (finished_at)
 #

plugins/discourse-calendar/db/migrate/20250919094856_add_distinct_on_optimization_index_to_event_dates.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+class AddDistinctOnOptimizationIndexToEventDates < ActiveRecord::Migration[8.0]
+  def change
+    add_index :discourse_calendar_post_event_dates,
+              %i[event_id finished_at starts_at],
+              name: "index_discourse_calendar_post_event_dates_on_event_id_and_dates",
+              order: {
+                finished_at: :desc,
+                starts_at: :desc,
+              }
+  end
+end

plugins/discourse-calendar/lib/discourse_post_event/event_finder.rb

@@ -23,7 +23,6 @@ module DiscoursePostEvent
       DiscoursePostEvent::Event
         .visible
         .open
-        .includes(:event_dates, :post, post: :topic)
         .joins(post: :topic)
         .merge(Post.secured(guardian))
         .merge(topics.or(pms))