Azure Synapse表截断事务持续挂起（队列状态）问题咨询

状态值含义补充 #

• sys.dm_pdw_exec_requests中status = 'Suspended'：请求已被系统接收，但因等待必要资源（锁、查询槽、系统资源等）暂时无法继续执行。
• sys.dm_pdw_waits中state = 'Queued'：请求处于内部等待队列，尚未被调度到计算节点执行；priority = 8属于Synapse默认低优先级层级（优先级范围1-10，数值越小优先级越高）。

关键排查查询语句 #

1. 获取挂起截断请求的详细等待信息 #

关联请求与等待视图，定位具体等待的资源类型和对象：

SELECT
    r.request_id,
    r.command,
    r.status,
    r.start_time,
    w.wait_type,
    w.state,
    w.priority,
    w.resource_type,
    w.resource_database_id,
    OBJECT_NAME(w.resource_associated_entity_id, w.resource_database_id) AS target_table
FROM sys.dm_pdw_exec_requests r
JOIN sys.dm_pdw_waits w ON r.request_id = w.request_id
WHERE r.status = 'Suspended'
  AND r.command LIKE '%TRUNCATE TABLE%'
ORDER BY r.start_time DESC;

2. 检查目标表的锁冲突情况 #

如果等待类型涉及锁，查询当前持有表锁的会话：

SELECT
    l.request_id,
    l.resource_type,
    OBJECT_NAME(l.resource_associated_entity_id, l.resource_database_id) AS locked_table,
    l.request_mode,
    l.request_status,
    s.session_id,
    s.login_name,
    s.app_name
FROM sys.dm_pdw_lock_wait_stats l
JOIN sys.dm_pdw_exec_sessions s ON l.request_id = s.request_id
WHERE OBJECT_NAME(l.resource_associated_entity_id, l.resource_database_id) IN ('表名1', '表名2')
ORDER BY l.request_id;

3. 查看系统资源占用与查询槽情况 #

检查计算节点的资源剩余量，确认是否因资源耗尽导致请求排队：

SELECT
    node_id,
    cpu_percent = record_xml.value('(./Record/SchedulerMonitorEvent/SystemHealth/ProcessUtilization)[1]', 'int'),
    memory_usage_percent = record_xml.value('(./Record/SchedulerMonitorEvent/SystemHealth/AvailableMemoryBytes)[1]', 'bigint') / 
                          record_xml.value('(./Record/SchedulerMonitorEvent/SystemHealth/TotalMemoryBytes)[1]', 'bigint') * 100,
    used_query_slots = record_xml.value('(./Record/SchedulerMonitorEvent/QueryPoolUsage/UsedSlots)[1]', 'int'),
    available_query_slots = record_xml.value('(./Record/SchedulerMonitorEvent/QueryPoolUsage/AvailableSlots)[1]', 'int')
FROM sys.dm_pdw_nodes_os_ring_buffers
CROSS APPLY (SELECT CAST(record AS XML) AS record_xml) AS r
WHERE record_xml.value('(./Record/@id)[1]', 'int') = 1
ORDER BY node_id;

4. 关联ADF流水线的会话上下文 #

查询来自Azure Data Factory的会话，确认是否有流水线其他步骤占用资源：

SELECT
    s.session_id,
    s.app_name,
    r.request_id,
    r.command,
    r.status,
    r.start_time
FROM sys.dm_pdw_exec_sessions s
JOIN sys.dm_pdw_exec_requests r ON s.session_id = r.session_id
WHERE s.app_name LIKE '%Azure Data Factory%'
ORDER BY r.start_time DESC;

临时缓解建议 #

• 终止占用锁的异常会话：若查询到长期持有表锁的会话，可执行KILL '目标request_id';终止（注意评估数据一致性风险）。
• 提升截断操作优先级：如果截断属于高优先级任务，执行前设置优先级：

SET QUERY_PRIORITY 1;
TRUNCATE TABLE 目标表名;

• 调整ADF流水线并发：避免同一时间对多表执行截断+插入操作，降低流水线并发度减少资源竞争。

内容的提问来源于stack exchange，提问作者seeess1