diff --git a/src/blackboard/db.py b/src/blackboard/db.py
index b2a77c6..6433b2c 100644
--- a/src/blackboard/db.py
+++ b/src/blackboard/db.py
@@ -96,20 +96,14 @@ def _batch_update_card_id(conn: sqlite3.Connection, table: str,
                            card_id: str, batch_size: int = 500) -> None:
     """分批更新 card_id，避免大表长时间锁"""
     while True:
-        conn.execute(
+        cursor = conn.execute(
             f"UPDATE {table} SET card_id=? WHERE rowid IN ("
             f"SELECT rowid FROM {table} WHERE card_id IS NULL LIMIT {batch_size})",
             (card_id,),
         )
-        if conn.total_changes == 0:
+        if cursor.rowcount == 0:
             break
         conn.commit()
-        # 检查是否还有剩余
-        row = conn.execute(
-            f"SELECT COUNT(*) as cnt FROM {table} WHERE card_id IS NULL"
-        ).fetchone()
-        if not row or row["cnt"] == 0:
-            break
 
 
 def _safe_add_column(conn: sqlite3.Connection, table: str,