Look through whole db for user timelines.

They already have an index that's good enough.

lib/pleroma/web/activity_pub/activity_pub.ex

@@ -157,6 +157,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
   defp restrict_favorited_by(query, _), do: query
 
   # Only search through last 100_000 activities by default
+  defp restrict_recent(query, %{"whole_db" => true}), do: query
   defp restrict_recent(query, _) do
     since = (Repo.aggregate(Activity, :max, :id) || 0) - 100_000
 

lib/pleroma/web/mastodon_api/mastodon_api_controller.ex

@@ -122,6 +122,7 @@ defmodule Pleroma.Web.MastodonAPI.MastodonAPIController do
       params = params
       |> Map.put("type", ["Create", "Announce"])
       |> Map.put("actor_id", ap_id)
+      |> Map.put("whole_db", true)
 
       activities = ActivityPub.fetch_activities([], params)
       |> Enum.reverse

lib/pleroma/web/twitter_api/twitter_api_controller.ex

@@ -68,7 +68,7 @@ defmodule Pleroma.Web.TwitterAPI.Controller do
   def user_timeline(%{assigns: %{user: user}} = conn, params) do
     case TwitterAPI.get_user(user, params) do
       {:ok, target_user} ->
-        params = Map.merge(params, %{"actor_id" => target_user.ap_id})
+        params = Map.merge(params, %{"actor_id" => target_user.ap_id, "whole_db" => true})
         statuses  = TwitterAPI.fetch_user_statuses(user, params)
         conn
         |> json_reply(200, statuses |> Poison.encode!)