Cleanup previous PR

Use a dedicated API for better performance when calculating author sorts

src/calibre/db/cache.py

@@ -1075,6 +1075,20 @@ class Cache:
             return {aid:af.author_data(aid) for aid in af.table.id_map}
         return {aid:af.author_data(aid) for aid in author_ids if aid in af.table.id_map}
 
+    @read_api
+    def author_sorts(self, author_ids=None) -> dict[int, str]:
+        '''
+        Return author sorts for specified authors.
+
+        If no authors with the specified ids are found an empty dictionary is
+        returned. If author_ids is None, data for all authors is returned.
+        '''
+        af = self.fields['authors']
+        m = af.table.asort_map
+        if author_ids is None:
+            return m.copy()
+        return {aid:m[aid] for aid in author_ids if aid in m}
+
     @read_api
     def format_hash(self, book_id, fmt):
         ''' Return the hash of the specified format for the specified book. The

src/calibre/db/tests/writing.py

@@ -789,6 +789,8 @@ class WritingTest(BaseTest):
                          'Setting the author link to the same value as before, incorrectly marked some books as dirty')
         sdata = {aid:f'{aid}, changed' for aid in adata}
         self.assertEqual({1,2,3}, cache.set_sort_for_authors(sdata))
+        self.assertEqual(sdata, cache.author_sorts())
+        self.assertEqual(sdata, cache.author_sorts(sdata))
         for bid in (1, 2, 3):
             self.assertIn(', changed', cache.field_for('author_sort', bid))
         sdata = {aid:f'{aid*2 if aid == max(adata) else aid}, changed' for aid in adata}

src/calibre/gui2/library/bookshelf_view.py

@@ -805,15 +805,15 @@ def get_grouped_iterator(db: Cache, book_ids_iter: Iterable[int], field_name: st
             return
         case 'authors':
             field_id_map = db.get_id_map('authors')
-            author_sort_map = db.author_data(field_id_map)
+            author_sort_map = db.author_sorts()
             def gas(aid: int, au: str) -> str:
                 try:
-                    return author_sort_map[aid]['sort']
-                except Exception:
+                    return author_sort_map[aid]
+                except KeyError:
                     return au
-            sort_field_map = {au: gas(aid, au) for aid, au in field_id_map.items()}
-            sort_key = lambda x: sort_field_map[x]  # noqa: E731
+            sort_key = {au: gas(aid, au) for aid, au in field_id_map.items()}.__getitem__
             get_field_id_map = lambda: field_id_map  # noqa: E731
+            del gas
         case 'languages':
             lm = lang_map()
             formatter = lambda x: lm.get(x, x)  # noqa: E731