Stop metadata backup thread before bulk metadata edits to improve performance

src/calibre/gui2/actions/edit_metadata.py

@@ -184,7 +184,7 @@ class EditMetadataAction(InterfaceAction):
         self.gui.tags_view.blockSignals(True)
         try:
             changed = MetadataBulkDialog(self.gui, rows,
-                self.gui.library_view.model().db).changed
+                self.gui.library_view.model()).changed
         finally:
             self.gui.tags_view.blockSignals(False)
         if changed:

src/calibre/gui2/dialogs/metadata_bulk.py

@@ -142,12 +142,13 @@ class MetadataBulkDialog(QDialog, Ui_MetadataBulkDialog):
                             _('Append to field'),
                         ]
 
-    def __init__(self, window, rows, db):
+    def __init__(self, window, rows, model):
         QDialog.__init__(self, window)
         Ui_MetadataBulkDialog.__init__(self)
         self.setupUi(self)
-        self.db = db
-        self.ids = [db.id(r) for r in rows]
+        self.model = model
+        self.db = model.db
+        self.ids = [self.db.id(r) for r in rows]
         self.box_title.setText('<p>' +
                 _('Editing meta information for <b>%d books</b>') %
                 len(rows))
@@ -170,7 +171,7 @@ class MetadataBulkDialog(QDialog, Ui_MetadataBulkDialog):
         self.tag_editor_button.clicked.connect(self.tag_editor)
         self.autonumber_series.stateChanged[int].connect(self.auto_number_changed)
 
-        if len(db.custom_field_keys(include_composites=False)) == 0:
+        if len(self.db.custom_field_keys(include_composites=False)) == 0:
             self.central_widget.removeTab(1)
         else:
             self.create_custom_column_editors()
@@ -617,8 +618,15 @@ class MetadataBulkDialog(QDialog, Ui_MetadataBulkDialog):
         self.worker = Worker(args, self.db, self.ids,
                 getattr(self, 'custom_column_widgets', []),
                 Dispatcher(bb.accept, parent=bb))
+
+        # The metadata backup thread causes database commits
+        # which can slow down bulk editing of large numbers of books
+        self.model.stop_metadata_backup()
+        try:
             self.worker.start()
             bb.exec_()
+        finally:
+            self.model.start_metadata_backup()
 
         if self.worker.error is not None:
             return error_dialog(self, _('Failed'),

src/calibre/gui2/library/models.py

@@ -159,17 +159,24 @@ class BooksModel(QAbstractTableModel): # {{{
             # do something on the GUI thread. Deadlock.
         self.cover_cache = CoverCache(db, FunctionDispatcher(self.db.cover))
         self.cover_cache.start()
-        if self.metadata_backup is not None:
-            self.metadata_backup.stop()
-            # Would like to to a join here, but the thread might be waiting to
-            # do something on the GUI thread. Deadlock.
-        self.metadata_backup = MetadataBackup(db)
-        self.metadata_backup.start()
+        self.stop_metadata_backup()
+        self.start_metadata_backup()
         def refresh_cover(event, ids):
             if event == 'cover' and self.cover_cache is not None:
                 self.cover_cache.refresh(ids)
         db.add_listener(refresh_cover)
 
+    def start_metadata_backup(self):
+        self.metadata_backup = MetadataBackup(self.db)
+        self.metadata_backup.start()
+
+    def stop_metadata_backup(self):
+        if getattr(self, 'metadata_backup', None) is not None:
+            self.metadata_backup.stop()
+            # Would like to to a join here, but the thread might be waiting to
+            # do something on the GUI thread. Deadlock.
+
+
     def refresh_ids(self, ids, current_row=-1):
         rows = self.db.refresh_ids(ids)
         if rows:

src/calibre/gui2/preferences/misc.py

@@ -106,14 +106,13 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
         d.exec_()
 
     def compact(self, *args):
-        from calibre.library.caches import MetadataBackup
         m = self.gui.library_view.model()
-        if m.metadata_backup is not None:
-            m.metadata_backup.stop()
+        m.stop_metadata_backup()
+        try:
             d = CheckIntegrity(m.db, self)
             d.exec_()
-        m.metadata_backup = MetadataBackup(m.db)
-        m.metadata_backup.start()
+        finally:
+            m.start_metadata_backup()
 
     def open_config_dir(self, *args):
         from calibre.utils.config import config_dir