add index on submission events

app/models/submission_event.rb

@@ -15,6 +15,7 @@
 #
 # Indexes
 #
+#  index_submission_events_on_created_at     (created_at)
 #  index_submission_events_on_submission_id  (submission_id)
 #  index_submission_events_on_submitter_id   (submitter_id)
 #

db/migrate/20240228074821_add_index_on_submission_events.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class AddIndexOnSubmissionEvents < ActiveRecord::Migration[7.1]
+  def change
+    add_index :submission_events, :created_at
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.1].define(version: 2024_02_18_082157) do
+ActiveRecord::Schema[7.1].define(version: 2024_02_28_074821) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
@@ -136,6 +136,7 @@ ActiveRecord::Schema[7.1].define(version: 2024_02_18_082157) do
     t.datetime "event_timestamp", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.index ["created_at"], name: "index_submission_events_on_created_at"
     t.index ["submission_id"], name: "index_submission_events_on_submission_id"
     t.index ["submitter_id"], name: "index_submission_events_on_submitter_id"
   end