Walkthrough for the performance features of SQL Server on Linux
If you are a Linux user who is new to SQL Server, the following tasks walk you through some of the performance features. These are not unique or specific to Linux, but it helps to give you an idea of areas to investigate further. In each example, a link is provided to the depth documentation for that area.
The following examples use the AdventureWorks sample database. For instructions on how to obtain and install this sample database, see Restore a SQL Server database from Windows to Linux.
Create a Columnstore Index
A columnstore index is a technology for storing and querying large stores of data in a columnar data format, called a columnstore.
Add a Columnstore index to the SalesOrderDetail table by executing the T-SQL below:
CREATE NONCLUSTERED COLUMNSTORE INDEX [IX_SalesOrderDetail_ColumnStore] ON Sales.SalesOrderDetail (UnitPrice, OrderQty, ProductID) GO
Execute the following query that will use the Columnstore Index to scan the table:
SELECT ProductID, SUM(UnitPrice) SumUnitPrice, AVG(UnitPrice) AvgUnitPrice, SUM(OrderQty) SumOrderQty, AVG(OrderQty) AvgOrderQty FROM Sales.SalesOrderDetail GROUP BY ProductID ORDER BY ProductID
Verify that the Columnstore Index was used by looking up the object_id for the Columnstore index and confirming that it appears in the usage stats for the SalesOrderDetail table:
SELECT * FROM sys.indexes WHERE name = 'IX_SalesOrderDetail_ColumnStore' GO SELECT * FROM sys.dm_db_index_usage_stats WHERE database_id = DB_ID('AdventureWorks') AND object_id = OBJECT_ID('AdventureWorks.Sales.SalesOrderDetail');
Use In-Memory OLTP
SQL Server provides In-Memory OLTP features that can greatly improve the performance of application systems. This section of the Evaluation Guide will walk you through the steps to create a memory-optimized table stored in memory and a natively compiled stored procedure that can access the table without needing to be compiled or interpreted.
Configure Database for In-Memory OLTP
It’s recommended to set the database to a compatibility level of at least 130 to use In-Memory OLTP. Use the query below to check the current compatibility level of AdventureWorks:
USE AdventureWorks GO SELECT d.compatibility_level FROM sys.databases as d WHERE d.name = Db_Name(); GO
If necessary, update the level to 130:
ALTER DATABASE CURRENT SET COMPATIBILITY_LEVEL = 130; GO
When a transaction involves both a disk-based table and a memory-optimized table, it’s essential that the memory-optimized portion of the transaction operate at the transaction isolation level named SNAPSHOT. To reliably enforce this level for memory-optimized tables in a cross-container transaction, execute the following:
ALTER DATABASE CURRENT SET MEMORY_OPTIMIZED_ELEVATE_TO_SNAPSHOT=ON GO
Before you can create a memory-optimized table you must first create a Memory Optimized FILEGROUP and a container for data files:
ALTER DATABASE AdventureWorks ADD FILEGROUP AdventureWorks_mod CONTAINS memory_optimized_data GO ALTER DATABASE AdventureWorks ADD FILE (NAME='AdventureWorks_mod', FILENAME='/var/opt/mssql/data/AdventureWorks_mod') TO FILEGROUP AdventureWorks_mod GO
Create a Memory-Optimized Table
The primary store for memory-optimized tables is main memory and so unlike disk-based tables, data does not need to be read in from disk into memory buffers. To create a memory-optimized table, use the MEMORY_OPTIMIZED = ON clause.
Execute the following query to create the memory-optimized table dbo.ShoppingCart. As a default, the data will be persisted on disk for durability purposes (Note that DURABILITY can also be set to persist the schema only).
CREATE TABLE dbo.ShoppingCart ( ShoppingCartId INT IDENTITY(1,1) PRIMARY KEY NONCLUSTERED, UserId INT NOT NULL INDEX ix_UserId NONCLUSTERED HASH WITH (BUCKET_COUNT=1000000), CreatedDate DATETIME2 NOT NULL, TotalPrice MONEY ) WITH (MEMORY_OPTIMIZED=ON) GO
Insert some records into the table:
INSERT dbo.ShoppingCart VALUES (8798, SYSDATETIME(), NULL) INSERT dbo.ShoppingCart VALUES (23, SYSDATETIME(), 45.4) INSERT dbo.ShoppingCart VALUES (80, SYSDATETIME(), NULL) INSERT dbo.ShoppingCart VALUES (342, SYSDATETIME(), 65.4)
Natively compiled Stored Procedure
SQL Server supports natively compiled stored procedures that access memory-optimized tables. The T-SQL statements are compiled to machine code and stored as native DLLs, enabling faster data access and more efficient query execution than traditional T-SQL. Stored procedures that are marked with NATIVE_COMPILATION are natively compiled.
- Execute the following script to create a natively compiled stored procedure that inserts a large number of records into the ShoppingCart table:
CREATE PROCEDURE dbo.usp_InsertSampleCarts @InsertCount int WITH NATIVE_COMPILATION, SCHEMABINDING AS BEGIN ATOMIC WITH (TRANSACTION ISOLATION LEVEL = SNAPSHOT, LANGUAGE = N'us_english') DECLARE @i int = 0 WHILE @i < @InsertCount BEGIN INSERT INTO dbo.ShoppingCart VALUES (1, SYSDATETIME() , NULL) SET @i += 1 END END
Insert 1,000,000 rows:
EXEC usp_InsertSampleCarts 1000000
Verify the rows have been inserted:
SELECT COUNT(*) FROM dbo.ShoppingCart
Learn More About In-Memory OLTP
For more information about In-Memory OLTP, see the following topics:
- Quick Start 1: In-Memory OLTP Technologies for Faster Transact-SQL Performance
- Migrating to In-Memory OLTP
- Faster temp table and table variable by using memory optimization
- Monitor and Troubleshoot Memory Usage
- In-Memory OLTP (In-Memory Optimization)
Use Query Store
Query Store collects detailed performance information about queries, execution plans, and runtime statistics.
Query Store is not active by default and can be enabled with ALTER DATABASE:
ALTER DATABASE AdventureWorks SET QUERY_STORE = ON;
Run the following query to return information about queries and plans in the query store:
SELECT Txt.query_text_id, Txt.query_sql_text, Pl.plan_id, Qry.* FROM sys.query_store_plan AS Pl JOIN sys.query_store_query AS Qry ON Pl.query_id = Qry.query_id JOIN sys.query_store_query_text AS Txt ON Qry.query_text_id = Txt.query_text_id ;
Query Dynamic Management Views
Dynamic management views return server state information that can be used to monitor the health of a server instance, diagnose problems, and tune performance.
To query the dm_os_wait stats dynamic management view:
SELECT wait_type, wait_time_ms FROM sys.dm_os_wait_stats;