sys.dm_exec_query_statistics_xml (Transact-SQL)

Artikkeli
03/01/2023

Applies to: SQL Server 2016 (13.x) and later Azure SQL Database Azure SQL Managed Instance

Returns query execution plan for in-flight requests. Use this DMV to retrieve showplan XML with transient statistics.

Syntax

sys.dm_exec_query_statistics_xml(session_id)

Arguments

session_id
Is the session id executing the batch to be looked up. session_id is smallint. session_id can be obtained from the following dynamic management objects:

Table Returned

Column Name	Data Type	Description
session_id	smallint	ID of the session. Not nullable.
request_id	int	ID of the request. Not nullable.
sql_handle	varbinary(64)	Is a token that uniquely identifies the batch or stored procedure that the query is part of. Nullable.
plan_handle	varbinary(64)	Is a token that uniquely identifies a query execution plan for a batch that is currently executing. Nullable.
query_plan	xml	Contains the runtime Showplan representation of the query execution plan that is specified with plan_handle containing partial statistics. The Showplan is in XML format. One plan is generated for each batch that contains, for example ad hoc Transact-SQL statements, stored procedure calls, and user-defined function calls. Nullable.

Remarks

Important

Owning to a possible random access violation (AV) while executing a monitoring stored procedure with the sys.dm_exec_query_statistics_xml DMV, the Showplan XML attribute <ParameterList> value ParameterRuntimeValue was removed in SQL Server 2017 (14.x) CU 26 and SQL Server 2019 (15.x) CU 12. This value could be useful while troubleshooting long running stored procedures.

Starting with SQL Server 2017 (14.x) CU 31 and SQL Server 2019 (15.x) CU 19, the collection of the Showplan XML attribute <ParameterList> value ParameterRuntimeValue has been re-enabled with the inclusion of trace flag 2446. This trace flag enables the collection of the runtime parameter value at the cost of introducing additional overhead.

Warning

Trace Flag 2446 isn't meant to be enabled continuously in a production environment, but only for time-limited troubleshooting purposes. Using this trace flag will introduce additional and possibly significant CPU and memory overhead as we will create a Showplan XML fragment with runtime parameter information, whether the sys.dm_exec_query_statistics_xml DMV is called or not.

Note

Starting with SQL Server 2022 (16.x), Azure SQL Database, and Azure SQL Managed Instance, to accomplish this at the database level see the FORCE_SHOWPLAN_RUNTIME_PARAMETER_COLLECTION option in ALTER DATABASE SCOPED CONFIGURATION (Transact-SQL).

This system function is available starting with SQL Server 2016 (13.x) SP1. See KB 3190871

This system function works under both standard and lightweight query execution statistics profiling infrastructure. For more information, see Query Profiling Infrastructure.

Under the following conditions, no Showplan output is returned in the query_plan column of the returned table for sys.dm_exec_query_statistics_xml:

If the query plan that corresponds to the specified session_id is no longer executing, the query_plan column of the returned table is null. For example, this condition may occur if there is a time delay between when the plan handle was captured and when it was used with sys.dm_exec_query_statistics_xml.

Due to a limitation in the number of nested levels allowed in the xml data type, sys.dm_exec_query_statistics_xml cannot return query plans that meet or exceed 128 levels of nested elements. In earlier versions of SQL Server, this condition prevented the query plan from returning and generates error 6335. In SQL Server 2005 (9.x) Service Pack 2 and later versions, the query_plan column returns NULL.

Permissions

On SQL Server, requires VIEW SERVER STATE permission on the server.
On SQL Database Premium Tiers, requires the VIEW DATABASE STATE permission in the database. On SQL Database Standard and Basic Tiers, requires the Server admin or a Microsoft Entra admin account.

Permissions for SQL Server 2022 and later

Requires VIEW SERVER PERFORMANCE STATE permission on the server.

Examples

A. Looking at live query plan and execution statistics for a running batch

The following example queries sys.dm_exec_requests to find the interesting query and copy its session_id from the output.

SELECT * FROM sys.dm_exec_requests;  
GO

Then, to obtain the live query plan and execution statistics, use the copied session_id with system function sys.dm_exec_query_statistics_xml.

--Run this in a different session than the session in which your query is running.
SELECT * FROM sys.dm_exec_query_statistics_xml(< copied session_id >);  
GO

Or combined for all running requests.

--Run this in a different session than the session in which your query is running.
SELECT 
	eqs.query_plan, 
	er.session_id, 
	er.request_id, 
	er.database_id,
	er.start_time,
	er.[status], 
	er.wait_type,
	er.wait_resource, 
	er.last_wait_type,
	(er.cpu_time/1000) AS cpu_time_sec,
	(er.total_elapsed_time/1000)/60 AS elapsed_time_minutes,
	(er.logical_reads*8)/1024 AS logical_reads_KB,
	er.granted_query_memory,
	er.dop,
	er.row_count, 
	er.query_hash, 
	er.query_plan_hash
FROM sys.dm_exec_requests er
	CROSS APPLY sys.dm_exec_query_statistics_xml(session_id) eqs
WHERE er.session_id <> @@spid;
GO

Jaa