Restoring database: Improve performance by using SQLITE savepoints when restoring individual books. Fixes #2796 (massive performance improvement for restoring database)

src/calibre/db/restore.py

@@ -11,7 +11,7 @@ import shutil
 import sys
 import time
 import traceback
-from contextlib import suppress
+from contextlib import closing, suppress
 from operator import itemgetter
 from threading import Thread
 
@@ -296,7 +296,8 @@ class Restore(Thread):
         with suppress(FileNotFoundError):
             os.remove(os.path.join(notes_dest, NOTES_DB_NAME))
         db = Restorer(self.library_path)
-
+        with closing(db):
+            with db.new_api:
                 for i, book in enumerate(self.books):
                     try:
                         db.restore_book(book['id'], book['mi'], utcfromtimestamp(book['timestamp']), book['path'], book['formats'], book['annotations'])
@@ -306,11 +307,11 @@ class Restore(Thread):
                         traceback.print_exc()
                     self.progress_callback(book['mi'].title, i+1)
 
+            with db.new_api:
                 for field, lmap in self.link_maps.items():
                     with suppress(Exception):
                         db.set_link_map(field, {k:v[0] for k, v in lmap.items()})
             self.notes_errors = db.backend.restore_notes(self.progress_callback)
-        db.close()
 
     def replace_db(self):
         dbpath = os.path.join(self.src_library_path, 'metadata.db')