Oops. Restore removed call to commit in set_path and have set_path call dirtied. Also limit the rate of metadata backups

src/calibre/library/caches.py

@@ -48,6 +48,7 @@ class MetadataBackup(Thread): # {{{
                 time.sleep(2)
                 if not self.dump_func([id_]):
                     prints('Failed to backup metadata for id:', id_, 'again, giving up')
+            time.sleep(0.2) # Limit to five per second
 
 # }}}
 

src/calibre/library/database2.py

@@ -455,6 +455,8 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
                 self.add_format(id, format, stream, index_is_id=True,
                         path=tpath, notify=False)
         self.conn.execute('UPDATE books SET path=? WHERE id=?', (path, id))
+        self.dirtied([id], commit=False)
+        self.commit()
         self.data.set(id, self.FIELD_MAP['path'], path, row_is_id=True)
         # Delete not needed directories
         if current_path and os.path.exists(spath):