diff --git a/queries_to_answers.py b/queries_to_answers.py
index 68c8670..20c7475 100644
--- a/queries_to_answers.py
+++ b/queries_to_answers.py
@@ -12,26 +12,34 @@ from nizika_ai.talk import Talk
 
 def main (
 ) -> None:
-    DB.begin_transaction ()
     queries: list[Query] = Query.where ('answered', False).get ()
     if not queries:
         return
+
     query: Query = random.choice (queries)
-    user: User = query.user
-    user_name: str | None = None
-    if query.user_id is not None:
-        user_name = user.name
-    histories: list[History] = []
-    for history in query.answer_histories:
-        if history.query is not None:
-            histories.append ({ 'role': 'user', 'content': history.query.content })
-        histories.append ({ 'role': 'assistant', 'content': history.content })
-    for character in [Character.DEERJIKA, Character.GOATOH]:
-        if query.target_character & character.value:
-            add_answer (query, character, user_name, histories)
-    query.answered = True
-    query.save ()
-    DB.commit ()
+
+    DB.begin_transaction ()
+    try:
+        user_name = query.user.name if query.user_id else None
+
+        histories: list[History] = []
+        for history in query.answer_histories:
+            if history.query is not None:
+                histories.append ({ 'role': 'user', 'content': history.query.content })
+            histories.append ({ 'role': 'assistant', 'content': history.content })
+
+        for character in [Character.DEERJIKA, Character.GOATOH]:
+            if query.target_character & character.value:
+                add_answer (query, character, user_name, histories)
+
+        query.answered = True
+
+        query.save ()
+
+        DB.commit ()
+    except Exception:
+        DB.rollback ()
+        raise
 
 
 def add_answer (
@@ -41,11 +49,12 @@ def add_answer (
         histories:  list[History],
 ) -> None:
     message: str | list[dict[str, str | dict[str, str]]]
-    if query.image_url is None:
-        message = query.content
-    else:
+    if query.image_url:
         message = [{ 'type': 'text', 'text': query.content },
                    { 'type': 'image_url', 'image_url': query.image_url }]
+    else:
+        message = query.content
+
     answer = Answer ()
     answer.query_id = query.id
     answer.character = character.value
@@ -65,9 +74,10 @@ def add_answered_flags (
         answer_type = AnswerType (answer.answer_type)
     except Exception:
         return
-    if answer_type in [AnswerType.YOUTUBE_REPLY]:
+
+    if answer_type in (AnswerType.YOUTUBE_REPLY,):
         add_answered_flag (answer, Platform.YOUTUBE)
-    if answer_type in [AnswerType.BLUESKY_REPLY]:
+    if answer_type in (AnswerType.BLUESKY_REPLY,):
         add_answered_flag (answer, Platform.BLUESKY)