sys.dm_exec_cached_plans (Transact-SQL)

Artykuł
12/08/2014

Returns a row for each query plan that is cached by SQL Server for faster query execution. You can use this dynamic management view to find cached query plans, cached query text, the amount of memory taken by cached plans, and the reuse count of the cached plans.

bucketid

int

ID of the hash bucket in which the entry is cached. The value indicates a range from 0 through the hash table size for the type of cache.

For the SQL Plans and Object Plans caches, the hash table size can be up to 10007 on 32-bit systems and up to 40009 on 64-bit systems. For the Bound Trees cache, the hash table size can be up to 1009 on 32-bit systems and up to 4001 on 64-bit systems. For the Extended Stored Procedures cache the hash table size can be up to 127 on 32-bit and 64-bit systems.

refcounts

int

Number of cache objects that are referencing this cache object. Refcounts must be at least 1 for an entry to be in the cache.

usecounts

int

Number of times the cache object has been looked up. Not incremented when parameterized queries find a plan in the cache. Can be incremented multiple times when using showplan.

size_in_bytes

int

Number of bytes consumed by the cache object.

memory_object_address

varbinary(8)

Memory address of the cached entry. This value can be used with sys.dm_os_memory_objects to get the memory breakdown of the cached plan and with sys.dm_os_memory_cache_entries_entries to obtain the cost of caching the entry.

cacheobjtype

nvarchar(34)

Type of object in the cache. The value can be one of the following:

Compiled Plan
Compiled Plan Stub
Parse Tree
Extended Proc
CLR Compiled Func
CLR Compiled Proc

objtype

nvarchar(16)

Type of object. The value can be one of the following:

Value	Description
Proc	Stored procedure
Prepared	Prepared statement
Adhoc	Ad hoc query1
ReplProc	Replication-filter-procedure
Trigger	Trigger
View	View
Default	Default
UsrTab	User table
SysTab	System table
Check	CHECK constraint
Rule	Rule

plan_handle

varbinary(64)

Identifier for the in-memory plan. This identifier is transient and remains constant only while the plan remains in the cache. This value may be used with the following dynamic management functions:

sys.dm_exec_sql_text

sys.dm_exec_query_plan

sys.dm_exec_plan_attributes

pool_id

int

The ID of the resource pool against which this plan memory usage is accounted for.

1 Refers to Transact-SQL submitted as language events by using osql or sqlcmd instead of as remote procedure calls.

Permissions

Requires VIEW SERVER STATE permission on the server.

Examples

A. Returning the batch text of cached entries that are reused

The following example returns the SQL text of all cached entries that have been used more than once.

SELECT usecounts, cacheobjtype, objtype, text 
FROM sys.dm_exec_cached_plans 
CROSS APPLY sys.dm_exec_sql_text(plan_handle) 
WHERE usecounts > 1 
ORDER BY usecounts DESC;
GO

B. Returning query plans for all cached triggers

The following example returns the query plans of all cached triggers.

SELECT plan_handle, query_plan, objtype 
FROM sys.dm_exec_cached_plans 
CROSS APPLY sys.dm_exec_query_plan(plan_handle) 
WHERE objtype ='Trigger';
GO

C. Returning the SET options with which the plan was compiled

The following example returns the SET options with which the plan was compiled. The sql_handle for the plan is also returned. The PIVOT operator is used to output the set_options and sql_handle attributes as columns rather than as rows. For more information about the value returned in set_options, see sys.dm_exec_plan_attributes (Transact-SQL).

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

D. Returning the memory breakdown of all cached compiled plans

The following example returns a breakdown of the memory used by all compiled plans in the cache.

SELECT plan_handle, ecp.memory_object_address AS CompiledPlan_MemoryObject, 
    omo.memory_object_address, pages_allocated_count, type, page_size_in_bytes 
FROM sys.dm_exec_cached_plans AS ecp 
JOIN sys.dm_os_memory_objects AS omo 
    ON ecp.memory_object_address = omo.memory_object_address 
    OR ecp.memory_object_address = omo.parent_address
WHERE cacheobjtype = 'Compiled Plan';
GO