From 8ce3660c87db9487e09bf074f60cf2764a8ff8df Mon Sep 17 00:00:00 2001
From: yuetsh <517252939@qq.com>
Date: Tue, 4 Aug 2026 01:08:06 -0600
Subject: [PATCH] =?UTF-8?q?fix(achievement):=20=E5=85=83=E6=8C=87=E6=A0=87?=
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---
 achievement/checker.py | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/achievement/checker.py b/achievement/checker.py
index 6138b92..0ed7fa3 100644
--- a/achievement/checker.py
+++ b/achievement/checker.py
@@ -84,13 +84,21 @@ def run_for_submission(user, submission):
         return []
 
     # 第二轮：只重算元指标、只判定依赖元指标的成就，不再有第三轮
-    for key in META_METRICS:
-        value = METRIC_REGISTRY[key].recompute(user)
-        if value is None:
-            stat.metrics.pop(key, None)
-        else:
-            stat.metrics[key] = value
-    stat.save(update_fields=["metrics", "update_time"])
+    meta_values = {key: METRIC_REGISTRY[key].recompute(user) for key in META_METRICS}
+
+    # 必须重新取锁并重新读一次 stat：上面那个 stat 对象的 metrics 是解锁前的快照，
+    # 直接 save 会把整份字典写回，覆盖掉并发判题在这期间已提交的增量
+    # （同一用户两次提交并发判题时会让提交数/AC 数静默倒退，且无定期重算兜底）。
+    # 这里只合并元指标那几个 key。
+    with transaction.atomic():
+        stat = UserStat.objects.select_for_update().get(user=user)
+        for key, value in meta_values.items():
+            if value is None:
+                stat.metrics.pop(key, None)
+            else:
+                stat.metrics[key] = value
+        stat.save(update_fields=["metrics", "update_time"])
+
     second = unlock(user, evaluate(user, stat.metrics, only_metrics=META_METRICS))
 
     return first + second