# BufferPin: BufferPin

> 等待获取 buffer 上的独占 pin。
---

<div class="event-kicker">PostgreSQL 等待事件档案</div>
<div class="event-identity">
  <span>类别<strong>BufferPin</strong></span>
  <span>事件<strong><code>BufferPin</code></strong></span>
  <span>版本<strong>PG 13-18</strong></span>
  <span>证据<strong>2 个源码位置</strong></span>
</div>

## 官方描述译文 {#official-description}

等待获取 buffer 上的独占 pin。

| PG 13 | PG 14 | PG 15 | PG 16 | PG 17 | PG 18 |
| :---: | :---: | :---: | :---: | :---: | :---: |
| ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |

## 触发机制 {#mechanism}

`WAIT_EVENT_BUFFER_PIN` 位于 `src/backend/storage/buffer/bufmgr.c:5819`，是经 grep 核验的报告路径。公共身份/资源映射位于 `src/backend/utils/activity/wait_event_names.txt:286`。探针覆盖的操作是：等待获取 buffer 上的独占 pin。缓冲区管理器需要独占 pin，但另一个后端仍在同一共享缓冲区上持有 pin；当前后端会休眠到最后一个冲突 pin 被释放。

## 正常还是麻烦？ {#normal-vs-trouble}

- <span class="severity-normal">**正常:**</span> 扫描或索引维护期间，孤立的亚秒级样本可能正常。
- <span class="severity-watch">**需要调查:**</span> 等待超过一秒就值得怀疑，尤其要检查游标或空闲事务是否持续钉住页面。

## 诊断 SQL {#diagnostic-sql}

```sql {title="正在等待 BufferPin/BufferPin 的会话"}
SELECT pid, backend_type, usename, datname, application_name,
       state, now() - query_start AS query_age,
       now() - xact_start AS xact_age,
       wait_event_type, wait_event,
       pg_blocking_pids(pid) AS blocking_pids,
       left(query, 160) AS query
FROM pg_stat_activity
WHERE wait_event_type = 'BufferPin'
  AND wait_event = 'BufferPin'
ORDER BY query_age DESC NULLS LAST;
```

```sql {title="当前 BufferPin 等待分布"}
SELECT wait_event, count(*) AS waiting_sessions,
       count(*) FILTER (WHERE state = 'active') AS active_waiters,
       max(now() - query_start) AS oldest_query
FROM pg_stat_activity
WHERE wait_event_type = 'BufferPin'
GROUP BY wait_event
ORDER BY waiting_sessions DESC, wait_event;
```

```sql {title="这些会话的锁与关系上下文"}
SELECT a.pid, l.locktype, l.mode, l.granted, l.fastpath,
       d.datname, n.nspname, c.relname,
       l.page, l.tuple, l.virtualxid, l.transactionid,
       l.classid, l.objid, l.objsubid
FROM pg_stat_activity AS a
LEFT JOIN pg_locks AS l ON l.pid = a.pid
LEFT JOIN pg_database AS d ON d.oid = l.database
LEFT JOIN pg_class AS c
  ON c.oid = l.relation
 AND l.database = (
       SELECT oid FROM pg_database WHERE datname = current_database()
     )
LEFT JOIN pg_namespace AS n ON n.oid = c.relnamespace
WHERE a.wait_event_type = 'BufferPin'
  AND a.wait_event = 'BufferPin'
ORDER BY a.pid, l.granted, l.locktype, l.mode;
```

## 处置建议 {#response}

1. 保全等待查询与关系上下文。
2. 查找访问同一关系的长游标与 idle in transaction 会话。
3. 确认最安全的持有者或维护受害者后再取消。

## 源码证据 {#source}

- [PostgreSQL 18.6 · src/backend/storage/buffer/bufmgr.c:5819](https://github.com/postgres/postgres/blob/REL_18_6/src/backend/storage/buffer/bufmgr.c#L5819) — `WAIT_EVENT_BUFFER_PIN`
- [PostgreSQL 18.6 · src/backend/utils/activity/wait_event_names.txt:286](https://github.com/postgres/postgres/blob/REL_18_6/src/backend/utils/activity/wait_event_names.txt#L286) — `BUFFER_PIN`

## 关联控制项与信号 {#related}

- **GUC:** 无直接关联项。
- **指标:** [[metric:waiting_sessions]](/zh/metric/waiting-sessions/) · [[metric:wait_event_share]](/zh/metric/wait-event-share/)

---

反链：

- [BufferPin](/zh/bufferpin/)