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sql-server - 扩展事件中的死锁图未显示

问题描述

我有这个查询来自“Sql Server 2017 Query Performance Tuning”（一本书）。这本书的代码可以在这里找到：https ://github.com/Apress/sql-server-2017-query-perf-tuning

DECLARE @path NVARCHAR(260)
--to retrieve the local path of system_health files 
SELECT @path = dosdlc.path
FROM sys.dm_os_server_diagnostics_log_configurations AS dosdlc;

SELECT @path = @path + N'system_health_*';

WITH fxd
AS (SELECT CAST(fx.event_data AS XML) AS Event_Data
    FROM sys.fn_xe_file_target_read_file(@path,
                                         NULL,
                                         NULL,
                                         NULL) AS fx )
SELECT dl.deadlockgraph
FROM
(   SELECT dl.query('.') AS deadlockgraph
    FROM fxd
        CROSS APPLY event_data.nodes('(/event/data/value/deadlock)') AS d(dl) ) AS dl;

它应该从扩展事件中捕获死锁图。我刚刚按照这个示例生成了一个死锁（如何在 SQL Server 上模拟 DEADLOCK？）。

但是当我运行查询时，我得到一个空的结果集。

标签： sql-servertsqldatabase-deadlocksextended-events

解决方案

看起来您的 XML 路径规范是针对 XE 环形缓冲区目标而不是文件目标的。试试下面的查询。

--Get xml_deadlock_report events from system_health session file target
WITH
      --get trace folder path and append session name with wildcard (assumes base file name is same as session name)
      all_trace_files AS (
        SELECT path + '\system_health*.xel' AS FileNamePattern
        FROM sys.dm_os_server_diagnostics_log_configurations
        )
      --get xml_deadlock_report events from all system_health trace files
    , deadlock_reports AS (
        SELECT CAST(event_data AS xml) AS deadlock_report_xml
        FROM all_trace_files
        CROSS APPLY sys.fn_xe_file_target_read_file ( FileNamePattern, NULL, NULL, NULL) AS trace_records
        WHERE trace_records.object_name like 'xml_deadlock_report'
    )
SELECT
      deadlock_report_xml.value('(/event/@timestamp)[1]', 'datetime2') AS UtcTimestamp
    , deadlock_report_xml AS DeadlockReportXml
FROM deadlock_reports;

要在 SSMS 中查看图形死锁报告，请event/data/value从 XML 文档的开始/结束处删除开始/结束标记，并将其另存为扩展名为“.xdl”的文件。然后在 SSMS 中打开文件以查看死锁图。

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