sys.dm_exec_plan_attributes (Transact-SQL)

Άρθρο
02/27/2023

Applies to: SQL Server

Returns one row per plan attribute for the plan specified by the plan handle. You can use this table-valued function to get details about a particular plan, such as the cache key values or the number of current simultaneous executions of the plan.

Note

Some of the information returned through this function maps to the sys.syscacheobjects backward compatibility view.

Syntax

sys.dm_exec_plan_attributes ( plan_handle )

Arguments

plan_handle
Uniquely identifies a query plan for a batch that has executed and whose plan resides in the plan cache. plan_handle is varbinary(64). The plan handle can be obtained from the sys.dm_exec_cached_plans dynamic management view.

Table Returned

Column name	Data type	Description
attribute	varchar(128)	Name of the attribute associated with this plan. The table immediately below this one lists the possible attributes, their data types, and their descriptions.
value	sql_variant	Value of the attribute that is associated with this plan.
is_cache_key	bit	Indicates whether the attribute is used as part of the cache lookup key for the plan.

From the above table, attribute can have the following values:

Attribute	Data type	Description
set_options	int	Indicates the option values that the plan was compiled with.
objectid	int	One of the main keys used for looking up an object in the cache. This is the object ID stored in sys.objects for database objects (procedures, views, triggers, and so on). For plans of type "Adhoc" or "Prepared", it is an internal hash of the batch text.
dbid	int	Is the ID of the database containing the entity the plan refers to. For ad hoc or prepared plans, it is the database ID from which the batch is executed.
dbid_execute	int	For system objects stored in the Resource database, the database ID from which the cached plan is executed. For all other cases, it is 0.
user_id	int	Value of -2 indicates that the batch submitted does not depend on implicit name resolution and can be shared among different users. This is the preferred method. Any other value represents the user ID of the user submitting the query in the database.
language_id	smallint	ID of the language of the connection that created the cache object. For more information, see sys.syslanguages (Transact-SQL).
date_format	smallint	Date format of the connection that created the cache object. For more information, see SET DATEFORMAT (Transact-SQL).
date_first	tinyint	Date first value. For more information, see SET DATEFIRST (Transact-SQL).
compat_level	tinyint	Represents the compatibility level set in the database in whose context the query plan was compiled. The compatibility level returned is the compatibility level of the current database context for adhoc statements, and is unaffected by the query hint QUERY_OPTIMIZER_COMPATIBILITY_LEVEL_n. For statements contained in a stored procedure or function it corresponds to the compatibility level of the database in which the stored procedure or function is created.
status	int	Internal status bits that are part of the cache lookup key.
required_cursor_options	int	Cursor options specified by the user such as the cursor type.
acceptable_cursor_options	int	Cursor options that SQL Server may implicitly convert to in order to support the execution of the statement. For example, the user may specify a dynamic cursor, but the query optimizer is permitted to convert this cursor type to a static cursor.
merge_action_type	smallint	The type of trigger execution plan used as the result of a MERGE statement. 0 indicates a non-trigger plan, a trigger plan that does not execute as the result of a MERGE statement, or a trigger plan that executes as the result of a MERGE statement that only specifies a DELETE action. 1 indicates an INSERT trigger plan that runs as the result of a MERGE statement. 2 indicates an UPDATE trigger plan that runs as the result of a MERGE statement. 3 indicates a DELETE trigger plan that runs as the result of a MERGE statement containing a corresponding INSERT or UPDATE action. For nested triggers run by cascading actions, this value is the action of the MERGE statement that caused the cascade.
is_replication_specific	int	Represents that the session from which this plan was compiled is one that connected to the instance of SQL Server using an undocumented connection property which allows the server to identify the session as one created by replication components, so that the behavior of certain functional aspects of the server are changed according to what such replication component expects.
optional_spid	smallint	The connection session_id (spid) becomes part of the cache key in order to reduce the number of re-compiles. This prevents recompilations for a single session's re-use of a plan involving non-dynamically bound temp tables.
optional_clr_trigger_dbid	int	Only populated in the case of a CLR DML trigger. The ID of the database containing the entity. For any other object type, returns zero.
optional_clr_trigger_objid	int	Only populated in the case of a CLR DML trigger. The object ID stored in sys.objects. For any other object type, returns zero.
parent_plan_handle	varbinary(64)	Always NULL.
is_azure_user_plan	tinyint	1 for queries executed in an Azure SQL Database from a session initiated by a user. 0 for queries that have been executed from a session not initiated by an end user, but by applications running from within Azure infrastructure that issue queries for other purposes of collecting telemetry or executing administrative tasks. Customers are not charged for resources consumed by queries where is_azure_user_plan = 0. Azure SQL Database only.
inuse_exec_context	int	Number of currently executing batches that are using the query plan.
free_exec_context	int	Number of cached execution contexts for the query plan that are not being currently used.
hits_exec_context	int	Number of times the execution context was obtained from the plan cache and reused, saving the overhead of recompiling the SQL statement. The value is an aggregate for all batch executions so far.
misses_exec_context	int	Number of times that an execution context could not be found in the plan cache, resulting in the creation of a new execution context for the batch execution.
removed_exec_context	int	Number of execution contexts that have been removed because of memory pressure on the cached plan.
inuse_cursors	int	Number of currently executing batches containing one or more cursors that are using the cached plan.
free_cursors	int	Number of idle or free cursors for the cached plan.
hits_cursors	int	Number of times that an inactive cursor was obtained from the cached plan and reused. The value is an aggregate for all batch executions so far.
misses_cursors	int	Number of times that an inactive cursor could not be found in the cache.
removed_cursors	int	Number of cursors that have been removed because of memory pressure on the cached plan.
sql_handle	varbinary(64)	The SQL handle for the batch.

Permissions

On SQL Server, requires VIEW SERVER STATE permission.

On Azure SQL Database Basic, S0, and S1 service objectives, and for databases in elastic pools, the server admin account or the Microsoft Entra admin account is required. On all other SQL Database service objectives, the VIEW DATABASE STATE permission is required in the database.

Permissions for SQL Server 2022 and later

Requires VIEW SERVER PERFORMANCE STATE permission on the server.

Remarks

Set Options

Copies of the same compiled plan might differ only by the value in the set_options column. This indicates that different connections are using different sets of SET options for the same query. Using different sets of options is usually undesirable because it can cause extra compilations, less plan reuse, and plan cache inflation because of multiple copies of plans in the cache.

Evaluating Set Options

To translate the value returned in set_options to the options with which the plan was compiled, subtract the values from the set_options value, starting with the largest possible value, until you reach 0. Each value you subtract corresponds to an option that was used in the query plan. For example, if the value in set_options is 251, the options the plan was compiled with are ANSI_NULL_DFLT_ON (128), QUOTED_IDENTIFIER (64), ANSI_NULLS(32), ANSI_WARNINGS (16), CONCAT_NULL_YIELDS_NULL (8), Parallel Plan(2) and ANSI_PADDING (1).

Option	Value
ANSI_PADDING	1
ParallelPlan Indicates that the plan parallelism options have changed.	2
FORCEPLAN	4
CONCAT_NULL_YIELDS_NULL	8
ANSI_WARNINGS	16
ANSI_NULLS	32
QUOTED_IDENTIFIER	64
ANSI_NULL_DFLT_ON	128
ANSI_NULL_DFLT_OFF	256
NoBrowseTable Indicates that the plan does not use a work table to implement a FOR BROWSE operation.	512
TriggerOneRow Indicates that the plan contains single row optimization for AFTER trigger delta tables.	1024
ResyncQuery Indicates that the query was submitted by internal system stored procedures.	2048
ARITH_ABORT	4096
NUMERIC_ROUNDABORT	8192
DATEFIRST	16384
DATEFORMAT	32768
LanguageID	65536
UPON Indicates that the database option PARAMETERIZATION was set to FORCED when the plan was compiled.	131072
ROWCOUNT	Applies To: SQL Server 2012 (11.x) and later 262144

Cursors

Inactive cursors are cached in a compiled plan so that the memory used to store the cursor can be reused by concurrent users of cursors. For example, suppose that a batch declares and uses a cursor without deallocating it. If there are two users executing the same batch, there will be two active cursors. Once the cursors are deallocated (potentially in different batches), the memory used to store the cursor is cached and not released. This list of inactive cursors is kept in the compiled plan. The next time a user executes the batch, the cached cursor memory will be reused and initialized appropriately as an active cursor.

Evaluating Cursor Options

To translate the value returned in required_cursor_options and acceptable_cursor_options to the options with which the plan was compiled, subtract the values from the column value, starting with the largest possible value, until you reach 0. Each value you subtract corresponds to a cursor option that was used in the query plan.

Option	Value
None	0
INSENSITIVE	1
SCROLL	2
READ ONLY	4
FOR UPDATE	8
LOCAL	16
GLOBAL	32
FORWARD_ONLY	64
KEYSET	128
DYNAMIC	256
SCROLL_LOCKS	512
OPTIMISTIC	1024
STATIC	2048
FAST_FORWARD	4096
IN PLACE	8192
FOR select_statement	16384

Examples

A. Returning the attributes for a specific plan

The following example returns all plan attributes for a specified plan. The sys.dm_exec_cached_plans dynamic management view is queried first to obtain the plan handle for the specified plan. In the second query, replace <plan_handle> with a plan handle value from the first query.

SELECT plan_handle, refcounts, usecounts, size_in_bytes, cacheobjtype, objtype   
FROM sys.dm_exec_cached_plans;  
GO  
SELECT attribute, [value], is_cache_key  
FROM sys.dm_exec_plan_attributes(<plan_handle>);  
GO

B. Returning the SET options for compiled plans and the SQL handle for cached plans

The following example returns a value representing the options that each plan was compiled with. In addition, the SQL handle for all the cached plans is returned.

SELECT plan_handle, pvt.set_options, pvt.sql_handle  
FROM (  
    SELECT plan_handle, epa.attribute, epa.value   
    FROM sys.dm_exec_cached_plans   
        OUTER APPLY sys.dm_exec_plan_attributes(plan_handle) AS epa  
    WHERE cacheobjtype = 'Compiled Plan') AS ecpa   
PIVOT (MAX(ecpa.value) FOR ecpa.attribute IN ("set_options", "sql_handle")) AS pvt;  
GO

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