Run Tag tree updates once per transaction

src/documents/signals/handlers.py

@@ -19,6 +19,7 @@ from django.db import DatabaseError
 from django.db import close_old_connections
 from django.db import connections
 from django.db import models
+from django.db import transaction
 from django.db.models import Q
 from django.dispatch import receiver
 from django.utils import timezone
@@ -60,6 +61,8 @@ if TYPE_CHECKING:
 
 logger = logging.getLogger("paperless.handlers")
 
+_tag_tree_update_scheduled = False
+
 
 def add_inbox_tags(sender, document: Document, logging_group=None, **kwargs):
     if document.owner is not None:
@@ -944,3 +947,26 @@ def close_connection_pool_on_worker_init(**kwargs):
     for conn in connections.all(initialized_only=True):
         if conn.alias == "default" and hasattr(conn, "pool") and conn.pool:
             conn.close_pool()
+
+
+def schedule_tag_tree_update(**_kwargs):
+    """
+    Schedule a single Tag.update_tree() at transaction commit.
+
+    Treenode's default post_save hooks rebuild the entire tree on every save,
+    which is very slow for large tag sets so collapse to one update per
+    transaction.
+    """
+    global _tag_tree_update_scheduled
+    if _tag_tree_update_scheduled:
+        return
+    _tag_tree_update_scheduled = True
+
+    def _run():
+        global _tag_tree_update_scheduled
+        try:
+            Tag.update_tree()
+        finally:
+            _tag_tree_update_scheduled = False
+
+    transaction.on_commit(_run)