Use the actual max number of variable supported by the sqlite connection

src/calibre/db/backend.py

@@ -554,6 +554,10 @@ class DB:
             set_global_state(self)
         self.initialize_notes()
 
+    @property
+    def max_number_of_variables(self) -> int:
+        return self.conn.limit(apsw.SQLITE_LIMIT_VARIABLE_NUMBER)
+
     @property
     def last_expired_trash_at(self) -> float:
         return float(self.prefs['last_expired_trash_at'])

src/calibre/db/cache.py

@@ -918,7 +918,7 @@ class Cache:
                 books_by_year[year].add(book_id)
         else:
             books = tuple(restrict_to_books)
-            BATCH_SIZE = 900
+            BATCH_SIZE = self.backend.max_number_of_variables
             for i in range(0, len(books), BATCH_SIZE):
                 batch = books[i:i + BATCH_SIZE]
                 placeholders = '?,' * len(batch)
@@ -943,7 +943,7 @@ class Cache:
                 ans[(year, month)].add(book_id)
         else:
             books = tuple(restrict_to_books)
-            BATCH_SIZE = 900
+            BATCH_SIZE = self.backend.max_number_of_variables
             for i in range(0, len(books), BATCH_SIZE):
                 batch = books[i:i + BATCH_SIZE]
                 placeholders = '?,' * len(batch)

src/calibre/db/tests/reading.py

@@ -472,6 +472,7 @@ class ReadingTest(BaseTest):
         self.assertEqual(cache.books_by_year(restrict_to_books={1,2}), {2011: {1, 2}})
         self.assertEqual(cache.books_by_month(), {(2011, 8): {1}, (2011, 9): {2, 3}})
         self.assertEqual(cache.books_by_month(restrict_to_books={1,2}), {(2011, 8): {1}, (2011, 9): {2}})
+        self.assertEqual(cache.books_by_year(restrict_to_books=range(cache.backend.max_number_of_variables+200)), {2011: {1, 2, 3}})
 
     def test_author_sort_for_authors(self):  # {{{
         'Test getting the author sort for authors from the db'