sp_create_plan_guide_from_handle (Transact-SQL)

sp_create_plan_guide_from_handle (T...

Community Content

In this section

Statistics Annotations (0)

Click here to expand

Collapse All

Language Filter

SQL Server 2008 Books Online (November 2009)

sp_create_plan_guide_from_handle (Transact-SQL)

Updated: 31 October 2008

Creates one or more plan guides from a query plan in the plan cache. You can use this stored procedure to ensure the query optimizer always uses a specific query plan for a specified query. For more information about plan guides, see Understanding Plan Guides.

Topic link icon Transact-SQL Syntax Conventions

Syntax

sp_create_plan_guide_from_handle [ @name = ] N'plan_guide_name'
    , [ @plan_handle = ] plan_handle
    , [ [ @statement_start_offset = ] { statement_start_offset | NULL } ]

Arguments

[ @name = ] N'plan_guide_name': Is the name of the plan guide. Plan guide names are scoped to the current database. plan_guide_name must comply with the rules for identifiers and cannot start with the number sign (#). The maximum length of plan_guide_name is 124 characters.

[ @plan_handle = ] plan_handle: Identifies a batch in the plan cache. plan_handle is varbinary(64). plan_handle can be obtained from the sys.dm_exec_query_stats dynamic management view.

[ @statement_start_offset = ] { statement_start_offset | NULL } ]

Identifies the starting position of the statement within the batch of the specified plan_handle. statement_start_offset is int, with a default of NULL.

The statement offset corresponds to the statement_start_offset column in the sys.dm_exec_query_stats dynamic management view.

When NULL is specified or a statement offset is not specified, a plan guide is created for each statement in the batch using the query plan for the specified plan handle. The resulting plan guides are equivalent to plan guides that use the USE PLAN query hint to force the use of a specific plan.

Remarks

A plan guide cannot be created for all statement types. If a plan guide cannot be created for a statement in the batch, the stored procedure ignores the statement and continues to the next statement in the batch. If a statement occurs multiple times in the same batch, the plan for the last occurrence is enabled and previous plans for the statement are disabled. If no statements in the batch can be used in a plan guide, error 10532 is raised and the statement fails. We recommend that you always obtain the plan handle from the sys.dm_exec_query_stats dynamic management view to help avoid the possibility of this error.

Security Note:
sp_create_plan_guide_from_handle creates plan guides based on plans as they appear in the plan cache. This means that the batch text, Transact-SQL statements, and XML Showplan are taken character-by-character (including any literal values passed to the query) from the plan cache into the resulting plan guide. These text strings may contain sensitive information that is then stored in the metadata of the database. Users with appropriate permissions can view this information by using the sys.plan_guides catalog view and the Plan Guide Properties dialog box in SQL Server Management Studio. To ensure that sensitive information is not disclosed through a plan guide, we recommend reviewing the plan guides created from the plan cache.

Security Note:

sp_create_plan_guide_from_handle creates plan guides based on plans as they appear in the plan cache. This means that the batch text, Transact-SQL statements, and XML Showplan are taken character-by-character (including any literal values passed to the query) from the plan cache into the resulting plan guide. These text strings may contain sensitive information that is then stored in the metadata of the database. Users with appropriate permissions can view this information by using the sys.plan_guides catalog view and the Plan Guide Properties dialog box in SQL Server Management Studio. To ensure that sensitive information is not disclosed through a plan guide, we recommend reviewing the plan guides created from the plan cache.

Creating Plan Guides for Multiple Statements Within a Query Plan

Like sp_create_plan_guide, sp_create_plan_guide_from_handle removes the query plan for the targeted batch or module from the plan cache. This is done to ensure that all users begin using the new plan guide. When creating a plan guide for multiple statements within a single query plan, you can postpone the removal of the plan from the cache by creating all the plan guides in an explicit transaction. This method allows the plan to remain in the cache until the transaction is complete and a plan guide for each specified statement is created. See Example B.

Permissions

Requires VIEW_SERVER_STATE permission. In addition, individual permissions are required for each plan guide that is created by using sp_create_plan_guide_from_handle. To create a plan guide of type OBJECT requires ALTER permission on the referenced object. To create a plan guide of type SQL or TEMPLATE requires ALTER permission on the current database. To determine the plan guide type that will be created, run the following query:

SELECT cp.plan_handle, sql_handle, st.text, objtype 
FROM sys.dm_exec_cached_plans AS cp
JOIN sys.dm_exec_query_stats AS qs ON cp.plan_handle = qs.plan_handle
CROSS APPLY sys.dm_exec_sql_text(sql_handle) AS st;

In the row that contains the statement for which you are creating the plan guide, examine the objtype column in the result set. A value of Proc indicates the plan guide is of type OBJECT. Other values such as AdHoc or Prepared indicate the plan guide is of type SQL.

Examples

A. Creating a plan guide from a query plan in the plan cache

The following example creates a plan guide for a single SELECT statement by specifying a query plan from the plan cache. The example begins by executing a simple SELECT statement for which the plan guide will be created. The plan for this query is examined by using the sys.dm_exec_sql_text and sys.dm_exec_text_query_plan dynamic management views. The plan guide is then created for the query by specifying the query plan in the plan cache that is associated with the query. The final statement in the example verifies that the plan guide exists.

USE AdventureWorks;
GO
SELECT WorkOrderID, p.Name, OrderQty, DueDate
FROM Production.WorkOrder AS w 
JOIN Production.Product AS p ON w.ProductID = p.ProductID
WHERE p.ProductSubcategoryID > 4
ORDER BY p.Name, DueDate;
GO
-- Inspect the query plan by using dynamic management views.
SELECT * FROM sys.dm_exec_query_stats AS qs
CROSS APPLY sys.dm_exec_sql_text(sql_handle)
CROSS APPLY sys.dm_exec_text_query_plan(qs.plan_handle, qs.statement_start_offset, qs.statement_end_offset) AS qp
WHERE text LIKE N'SELECT WorkOrderID, p.Name, OrderQty, DueDate%';
GO
-- Create a plan guide for the query by specifying the query plan in the plan cache.
DECLARE @plan_handle varbinary(64);
DECLARE @offset int;
SELECT @plan_handle = plan_handle, @offset = qs.statement_start_offset
FROM sys.dm_exec_query_stats AS qs
CROSS APPLY sys.dm_exec_sql_text(sql_handle) AS st
CROSS APPLY sys.dm_exec_text_query_plan(qs.plan_handle, qs.statement_start_offset, qs.statement_end_offset) AS qp
WHERE text LIKE N'SELECT WorkOrderID, p.Name, OrderQty, DueDate%';

EXECUTE sp_create_plan_guide_from_handle 
    @name =  N'Guide1',
    @plan_handle = @plan_handle,
    @statement_start_offset = @offset;
GO
-- Verify that the plan guide is created.
SELECT * FROM sys.plan_guides
WHERE scope_batch LIKE N'SELECT WorkOrderID, p.Name, OrderQty, DueDate%';
GO

B. Creating multiple plan guides for a multistatement batch

The following example creates a plan guide for two statements within a multistatement batch. The plan guides are created within an explicit transaction so that the query plan for the batch is not removed from the plan cache after the first plan guide is created. The example begins by executing a multistatement batch. The plan for the batch is examined by using dynamic management views. Notice that a row for each statement in the batch is returned. A plan guide is then created for the first and third statements in the batch by specifying the @statement_start_offset parameter. The final statement in the example verifies that the plan guides exist.

USE AdventureWorks;
GO
SELECT * FROM Production.Product WHERE ProductSubcategoryID > 4;
SELECT * FROM Person.Address;
SELECT * FROM Production.Product WHERE ProductSubcategoryID > 10;
GO

-- Examine the query plans for this batch
SELECT * FROM sys.dm_exec_query_stats AS qs
CROSS APPLY sys.dm_exec_sql_text(sql_handle)
CROSS APPLY sys.dm_exec_text_query_plan(qs.plan_handle, qs.statement_start_offset, qs.statement_end_offset) AS qp
WHERE text LIKE N'SELECT * FROM Production.Product WHERE ProductSubcategoryID > 4%';
GO

-- Create plan guides for the first and third statements in the batch by specifying the statement offsets.
BEGIN TRANSACTION

DECLARE @plan_handle varbinary(64);
DECLARE @offset int;

SELECT @plan_handle = plan_handle, @offset = qs.statement_start_offset
FROM sys.dm_exec_query_stats AS qs
CROSS APPLY sys.dm_exec_sql_text(sql_handle) AS st
CROSS APPLY sys.dm_exec_text_query_plan(qs.plan_handle, qs.statement_start_offset, qs.statement_end_offset) AS qp
WHERE text LIKE N'SELECT * FROM Production.Product WHERE ProductSubcategoryID > 4%'
AND SUBSTRING(st.text, (qs.statement_start_offset/2) + 1,
                        ((CASE statement_end_offset 
                              WHEN -1 THEN DATALENGTH(st.text)
                              ELSE qs.statement_end_offset END 
                              - qs.statement_start_offset)/2) + 1)  like 'SELECT * FROM Production.Product WHERE ProductSubcategoryID > 4%'

EXECUTE sp_create_plan_guide_from_handle 
    @name =  N'Guide_Statement1_only',
    @plan_handle = @plan_handle,
    @statement_start_offset = @offset;

SELECT @plan_handle = plan_handle, @offset = qs.statement_start_offset
FROM sys.dm_exec_query_stats AS qs
CROSS APPLY sys.dm_exec_sql_text(sql_handle) AS st
CROSS APPLY sys.dm_exec_text_query_plan(qs.plan_handle, qs.statement_start_offset, qs.statement_end_offset) AS qp
WHERE text LIKE N'SELECT * FROM Production.Product WHERE ProductSubcategoryID > 4%'
AND SUBSTRING(st.text, (qs.statement_start_offset/2) + 1,
                        ((CASE statement_end_offset 
                              WHEN -1 THEN DATALENGTH(st.text)
                              ELSE qs.statement_end_offset END 
                              - qs.statement_start_offset)/2) + 1)  like 'SELECT * FROM Production.Product WHERE ProductSubcategoryID > 10%'

EXECUTE sp_create_plan_guide_from_handle 
    @name =  N'Guide_Statement3_only',
    @plan_handle = @plan_handle,
    @statement_start_offset = @offset;

COMMIT TRANSACTION
GO

-- Verify the plan guides are created.
SELECT * FROM sys.plan_guides;
GO

Creating Plan Guides for Multiple Statements Within a Query Plan

A. Creating a plan guide from a query plan in the plan cache

B. Creating multiple plan guides for a multistatement batch

Reference

Other Resources

Help and Information