add an index on notes(mid) so we can avoid the tablescan

pylib/anki/models.py

@@ -317,7 +317,6 @@ class ModelManager:
 
     def useCount(self, m: NoteType) -> Any:
         "Number of note using M."
-        print("useCount() is slow; prefer all_use_counts()")
         return self.col.db.scalar("select count() from notes where mid = ?", m["id"])
 
     # Copying

pylib/anki/rsbackend.py

@@ -656,7 +656,7 @@ class RustBackend:
                     json=bjson, preserve_usn_and_mtime=preserve_usn
                 )
             ),
-            release_gil=True
+            release_gil=True,
         ).add_or_update_notetype
         nt["id"] = id
 

rslib/src/storage/notetype/get_use_counts.sql

@@ -1,10 +1,13 @@
 select
   nt.id,
   nt.name,
-  count(n.id)
+  (
+    select
+      count(*)
+    from notes n
+    where
+      nt.id = n.mid
+  )
 from notetypes nt
-left join notes n on (n.mid = nt.id)
-group by
-  nt.id
 order by
   nt.name

rslib/src/storage/upgrades/schema11_downgrade.sql

@@ -6,6 +6,7 @@ drop table templates;
 drop table notetypes;
 drop table decks;
 drop index idx_cards_odid;
+drop index idx_notes_mid;
 update col
 set
   ver = 11;

rslib/src/storage/upgrades/schema15_upgrade.sql

@@ -35,6 +35,7 @@ create table decks (
   kind bytes not null
 );
 create unique index idx_decks_name on decks (name);
+create index idx_notes_mid on notes (mid);
 create index idx_cards_odid on cards (odid)
 where
   odid != 0;