[#3213] Experimental / debug feature: `database: [improved_hashtag_timeline: :preselect_hashtag_ids]`.

lib/pleroma/web/activity_pub/activity_pub.ex

@@ -787,6 +787,28 @@ defp restrict_hashtag_any(_query, %{tag: _tag, skip_preload: true}) do
   end
 
   defp restrict_hashtag_any(query, %{tag: [_ | _] = tags}) do
+    # TODO: refactor: debug / experimental feature
+    if Config.get([:database, :improved_hashtag_timeline]) == :preselect_hashtag_ids do
+      hashtag_ids =
+        from(ht in Pleroma.Hashtag,
+          where: fragment("name = ANY(?::citext[])", ^tags),
+          select: ht.id
+        )
+        |> Repo.all()
+
+      from(
+        [_activity, object] in query,
+        where:
+          fragment(
+            """
+            EXISTS (
+            SELECT 1 FROM hashtags_objects WHERE hashtag_id = ANY(?) AND object_id = ? LIMIT 1)
+            """,
+            ^hashtag_ids,
+            object.id
+          )
+      )
+    else
       from(
         [_activity, object] in query,
         where:
@@ -801,6 +823,7 @@ defp restrict_hashtag_any(query, %{tag: [_ | _] = tags}) do
           )
       )
     end
+  end
 
   defp restrict_hashtag_any(query, %{tag: tag}) when is_binary(tag) do
     restrict_hashtag_any(query, %{tag: [tag]})