Use desc id to sort instead of desc inserted_at

Should mean the same and is indexed.

lib/pleroma/web/activity_pub/activity_pub.ex

@@ -97,7 +97,7 @@ def delete(%Object{data: %{"id" => id, "actor" => actor}} = object, local \\ tru
   def fetch_activities_for_context(context) do
     query = from activity in Activity,
       where: fragment("?->>'type' = ? and ?->>'context' = ?", activity.data, "Create", activity.data, ^context),
-      order_by: [desc: :inserted_at]
+      order_by: [desc: :id]
     Repo.all(query)
   end
 

lib/pleroma/web/activity_pub/utils.ex

@@ -152,7 +152,7 @@ def fetch_latest_follow(%User{ap_id: follower_id},
     query = from activity in Activity,
       where: fragment("? @> ?", activity.data, ^%{type: "Follow", actor: follower_id,
                                                   object: followed_id}),
-      order_by: [desc: :inserted_at],
+      order_by: [desc: :id],
       limit: 1
     Repo.one(query)
   end

lib/pleroma/web/ostatus/ostatus_controller.ex

@@ -21,7 +21,7 @@ def feed(conn, %{"nickname" => nickname}) do
     query = from activity in Activity,
       where: fragment("?->>'actor' = ?", activity.data, ^user.ap_id),
       limit: 20,
-      order_by: [desc: :inserted_at]
+      order_by: [desc: :id]
 
     activities = query
     |> Repo.all