Using the Query Store with In-Memory OLTP

Applies to: SQL Server Azure SQL Database

SQL Server Query Store allows you to monitor the performance of natively compiled code for workloads running in-memory OLTP.
Compile and runtime statistics are collected and exposed the same way as for disk-based workloads.
When you migrate to in-memory OLTP you can continue using Query Store views in SQL Server Management Studio as well as custom scripts you have developed for disk-based workloads before migration. This saves your investment in learning Query Store technology and makes it generally usable for troubleshooting all type of workloads.
For general information on using the Query Store, see Monitoring Performance By Using the Query Store.

Using the Query Store with in-memory OLTP does not require any additional feature configuration. When you enable it on your database it will work for all types of workloads.
However, there are some specific aspects that users should be aware of when using Query Store with in-memory OLTP:

  • When Query Store is enabled, queries, plans and compile-time statistics are collected by default. However, runtime statistics collection is not activated unless you explicitly enable it with sys.sp_xtp_control_query_exec_stats (Transact-SQL).

  • When you set @new_collection_value to 0 Query Store will stop collecting runtime statistics for affected procedure or for the entire SQL Server instance.

  • The value configured with sys.sp_xtp_control_query_exec_stats (Transact-SQL) is not persisted. Make sure you check and configure again statistics collection after restarting SQL Server.

  • As in case with regular query statistics collection, performance may decrease when you use Query Store to track workload execution. You may want to consider enabling statistics collection only for an important subset of natively compiled stored procedures.

  • Queries and plans are captured and stored on the first native compilation and updated upon every recompilation.

  • If you enabled Query Store or cleared its content after all native stored procedure were compiled you must recompile them manually in order to make them captured by the Query Store. The same applies if you removed queries manually by using sp_query_store_remove_query (Transact-SQL) or sp_query_store_remove_plan (Transct-SQL). Use sp_recompile (Transact-SQL) to force procedure recompilation.

  • Query Store leverages plan generation mechanisms from in-memory OLTP to capture query execution plan during the compilation. Stored plan is semantically equivalent to one that you would get by using SET SHOWPLAN_XML ON with one difference; plans in Query Store are split and stored per individual statement.

  • When you run Query Store in a database with a mixed workload then you can use is_natively_compiled field from sys.query_store_plan (Transact-SQL) to quickly find query plans that are generated by the native code compilation.

  • Query Store capture mode (QUERY_CAPTURE_MODE parameter in ALTER TABLE statement) does not affect queries from natively compiled modules as they are always captured regardless of the configured value. This includes setting QUERY_CAPTURE_MODE = NONE.

  • The duration of query compilation captured by the Query Store includes only time spent in query optimization, before the native code was generated. More precisely, it doesn't include time for C code compilation and generation of internal structures necessary for C code generation.

  • Memory grants metrics within sys.query_store_runtime_stats (Transact-SQL) are not populated for natively compiled queries - their values are always 0. The memory grants columns are: avg_query_max_used_memory, last_query_max_used_memory, min_query_max_used_memory, max_query_max_used_memory, and stdev_query_max_used_memory.

Enabling and using Query Store with In-Memory OLTP

The following simple example demonstrates using Query Store with in-memory OLTP in an end-to-end user scenario. In this example we assume that a database (MemoryOLTP) is enabled for in-memory OLTP.
For more details on prerequisites for memory-optimized tables, see Creating a Memory-Optimized Table and a Natively Compiled Stored Procedure.

USE MemoryOLTP;  
-- Create a simple memory-optimized table   
    OrdDate DATETIME not null,   
    CustCode NVARCHAR(5) not null)   
-- Enable Query Store before native module compilation  
-- Create natively compiled stored procedure  
CREATE PROCEDURE dbo.OrderInsert(@OrdNo integer, @CustCode nvarchar(5))  
    LANGUAGE = N'English')  
    INSERT INTO dbo.Ord (OrdNo, CustCode, OrdDate)   
        VALUES (@OrdNo, @CustCode, @OrdDate);  
-- Enable runtime stats collection for queries from dbo.OrderInsert stored procedure  
DECLARE @db_id INT = DB_ID()  
DECLARE @proc_id INT = OBJECT_ID('dbo.OrderInsert');  
DECLARE @collection_enabled BIT;  
EXEC [sys].[sp_xtp_control_query_exec_stats] @new_collection_value = 1,   
    @database_id = @db_id, @xtp_object_id = @proc_id;  
-- Check the state of the collection flag  
EXEC sp_xtp_control_query_exec_stats @database_id = @db_id,   
    @xtp_object_id = @proc_id,   
    @old_collection_value= @collection_enabled output;  
SELECT @collection_enabled AS 'collection status';  
-- Execute natively compiled workload  
EXEC dbo.OrderInsert 1, 'A';  
EXEC dbo.OrderInsert 2, 'B';  
EXEC dbo.OrderInsert 3, 'C';  
EXEC dbo.OrderInsert 4, 'D';  
EXEC dbo.OrderInsert 5, 'E';  
-- Check Query Store Data  
-- Compile time data  
SELECT q.query_id, plan_id, object_id, query_hash, p.query_plan,  
    p.initial_compile_start_time, p.last_compile_start_time,   
    p.last_execution_time, p.avg_compile_duration,  
    p.last_force_failure_reason, p.force_failure_count  
FROM sys.query_store_query AS q  
JOIN sys.query_store_plan AS p   
    ON q.query_id = p.plan_id  
WHERE q.object_id = OBJECT_ID('dbo.OrderInsert');  
-- Get runtime stats  
-- Check count_executions field to verify that runtime statistics   
-- have been collected by the Query Store  
SELECT q.query_id, p.plan_id, object_id, rsi.start_time, rsi.end_time,    
    p.last_force_failure_reason, p.force_failure_count, rs.*  
FROM sys.query_store_query AS q  
JOIN sys.query_store_plan AS p   
    ON q.query_id = p.plan_id  
JOIN sys.query_store_runtime_stats AS rs   
    ON rs.plan_id = p.plan_id  
JOIN sys.query_store_runtime_stats_interval AS rsi   
    ON rs.runtime_stats_interval_id = rsi.runtime_stats_interval_id  
WHERE q.object_id = OBJECT_ID('dbo.OrderInsert');  

See Also

Monitoring Performance By Using the Query Store
Creating a Memory-Optimized Table and a Natively Compiled Stored Procedure
Best Practice with the Query Store
Query Store Stored Procedures (Transact-SQL)
Query Store Catalog Views (Transact-SQL)