In-Memory technologies in Azure SQL Database enable you to improve performance of your application, and potentially reduce cost of your database. By using In-Memory technologies in Azure SQL Database, you can achieve performance improvements with various workloads.
In this article you'll see two samples that illustrate the use of In-Memory OLTP, as well as columnstore indexes in Azure SQL Database.
For more information, see:
- In-Memory OLTP Overview and Usage Scenarios (includes references to customer case studies and information to get started)
- Documentation for In-Memory OLTP
- Columnstore Indexes Guide
- Hybrid transactional/analytical processing (HTAP), also known as real-time operational analytics
1. Install the In-Memory OLTP sample
You can create the AdventureWorksLT sample database with a few clicks in the Azure portal. Then, the steps in this section explain how you can enrich your AdventureWorksLT database with In-Memory OLTP objects and demonstrate performance benefits.
For a more simplistic, but more visually appealing performance demo for In-Memory OLTP, see:
In the Azure portal, create a Premium or Business Critical database on a server. Set the Source to the AdventureWorksLT sample database. For detailed instructions, see Create your first database in Azure SQL Database.
Connect to the database with SQL Server Management Studio (SSMS.exe).
Copy the In-Memory OLTP Transact-SQL script to your clipboard. The T-SQL script creates the necessary In-Memory objects in the AdventureWorksLT sample database that you created in step 1.
Paste the T-SQL script into SSMS, and then execute the script. The
MEMORY_OPTIMIZED = ONclause CREATE TABLE statements are crucial. For example:
CREATE TABLE [SalesLT].[SalesOrderHeader_inmem]( [SalesOrderID] int IDENTITY NOT NULL PRIMARY KEY NONCLUSTERED ..., ... ) WITH (MEMORY_OPTIMIZED = ON);
If you get error 40536 when you run the T-SQL script, run the following T-SQL script to verify whether the database supports In-Memory:
SELECT DatabasePropertyEx(DB_Name(), 'IsXTPSupported');
A result of 0 means that In-Memory isn't supported, and 1 means that it is supported. To diagnose the problem, ensure that the database is at the Premium service tier.
About the created memory-optimized items
Tables: The sample contains the following memory-optimized tables:
You can inspect memory-optimized tables through the Object Explorer in SSMS. Right-click Tables > Filter > Filter Settings > Is Memory Optimized. The value equals 1.
Or you can query the catalog views, such as:
SELECT is_memory_optimized, name, type_desc, durability_desc FROM sys.tables WHERE is_memory_optimized = 1;
Natively compiled stored procedure: You can inspect SalesLT.usp_InsertSalesOrder_inmem through a catalog view query:
SELECT uses_native_compilation, OBJECT_NAME(object_id), definition FROM sys.sql_modules WHERE uses_native_compilation = 1;
Run the sample OLTP workload
The only difference between the following two stored procedures is that the first procedure uses memory-optimized versions of the tables, while the second procedure uses the regular on-disk tables:
In this section, you see how to use the handy ostress.exe utility to execute the two stored procedures at stressful levels. You can compare how long it takes for the two stress runs to finish.
When you run ostress.exe, we recommend that you pass parameter values designed for both of the following:
- Run a large number of concurrent connections, by using -n100.
- Have each connection loop hundreds of times, by using -r500.
However, you might want to start with much smaller values like -n10 and -r50 to ensure that everything is working.
Script for ostress.exe
This section displays the T-SQL script that is embedded in our ostress.exe command line. The script uses items that were created by the T-SQL script that you installed earlier.
The following script inserts a sample sales order with five line items into the following memory-optimized tables:
DECLARE @i int = 0, @od SalesLT.SalesOrderDetailType_inmem, @SalesOrderID int, @DueDate datetime2 = sysdatetime(), @CustomerID int = rand() * 8000, @BillToAddressID int = rand() * 10000, @ShipToAddressID int = rand() * 10000; INSERT INTO @od SELECT OrderQty, ProductID FROM Demo.DemoSalesOrderDetailSeed WHERE OrderID= cast((rand()*60) as int); WHILE (@i < 20) begin; EXECUTE SalesLT.usp_InsertSalesOrder_inmem @SalesOrderID OUTPUT, @DueDate, @CustomerID, @BillToAddressID, @ShipToAddressID, @od; SET @i = @i + 1; end
To make the _ondisk version of the preceding T-SQL script for ostress.exe, you would replace both occurrences of the _inmem substring with _ondisk. These replacements affect the names of tables and stored procedures.
Install RML utilities and
Ideally, you would plan to run ostress.exe on an Azure virtual machine (VM). You would create an Azure VM in the same Azure geographic region where your AdventureWorksLT database resides. But you can run ostress.exe on your laptop instead.
On the VM, or on whatever host you choose, install the Replay Markup Language (RML) utilities. The utilities include ostress.exe.
For more information, see:
- The ostress.exe discussion in Sample Database for In-Memory OLTP.
- Sample Database for In-Memory OLTP.
- The blog for installing ostress.exe.
Run the _inmem stress workload first
You can use an RML Cmd Prompt window to run our ostress.exe command line. The command-line parameters direct
- Run 100 connections concurrently (-n100).
- Have each connection run the T-SQL script 50 times (-r50).
ostress.exe -n100 -r50 -S<servername>.database.windows.net -U<login> -P<password> -d<database> -q -Q"DECLARE @i int = 0, @od SalesLT.SalesOrderDetailType_inmem, @SalesOrderID int, @DueDate datetime2 = sysdatetime(), @CustomerID int = rand() * 8000, @BillToAddressID int = rand() * 10000, @ShipToAddressID int = rand()* 10000; INSERT INTO @od SELECT OrderQty, ProductID FROM Demo.DemoSalesOrderDetailSeed WHERE OrderID= cast((rand()*60) as int); WHILE (@i < 20) begin; EXECUTE SalesLT.usp_InsertSalesOrder_inmem @SalesOrderID OUTPUT, @DueDate, @CustomerID, @BillToAddressID, @ShipToAddressID, @od; set @i += 1; end"
To run the preceding ostress.exe command line:
Reset the database data content by running the following command in SSMS, to delete all the data that was inserted by any previous runs:
Copy the text of the preceding ostress.exe command line to your clipboard.
<placeholders>for the parameters -S -U -P -d with the correct real values.
Run your edited command line in an RML Cmd window.
Result is a duration
ostress.exe finishes, it writes the run duration as its final line of output in the RML Cmd window. For example, a shorter test run lasted about 1.5 minutes:
11/12/15 00:35:00.873 [0x000030A8] OSTRESS exiting normally, elapsed time: 00:01:31.867
Reset, edit for _ondisk, then rerun
After you have the result from the _inmem run, perform the following steps for the _ondisk run:
Reset the database by running the following command in SSMS to delete all the data that was inserted by the previous run:
Edit the ostress.exe command line to replace all _inmem with _ondisk.
Rerun ostress.exe for the second time, and capture the duration result.
Again, reset the database (for responsibly deleting what can be a large amount of test data).
Expected comparison results
Our In-Memory tests have shown that performance improved by nine times for this simplistic workload, with
ostress running on an Azure VM in the same Azure region as the database.
2. Install the In-Memory Analytics sample
In this section, you compare the IO and statistics results when you're using a columnstore index versus a traditional b-tree index.
For real-time analytics on an OLTP workload, it's often best to use a nonclustered columnstore index. For details, see Columnstore Indexes Described.
Prepare the columnstore analytics test
Use the Azure portal to create a fresh AdventureWorksLT database from the sample.
- Use that exact name.
- Choose any Premium service tier.
Copy the sql_in-memory_analytics_sample to your clipboard.
- The T-SQL script creates the necessary In-Memory objects in the AdventureWorksLT sample database that you created in step 1.
- The script creates the Dimension table and two fact tables. The fact tables are populated with 3.5 million rows each.
- The script might take 15 minutes to complete.
Paste the T-SQL script into SSMS, and then execute the script. The COLUMNSTORE keyword in the CREATE INDEX statement is crucial, as in:
CREATE NONCLUSTERED COLUMNSTORE INDEX ...;
Set AdventureWorksLT to compatibility level 130:
ALTER DATABASE AdventureworksLT SET compatibility_level = 130;
Level 130 is not directly related to In-Memory features. But level 130 generally provides faster query performance than 120.
Key tables and columnstore indexes
dbo.FactResellerSalesXL_CCI is a table that has a clustered columnstore index, which has advanced compression at the data level.
dbo.FactResellerSalesXL_PageCompressed is a table that has an equivalent regular clustered index, which is compressed only at the page level.
Key queries to compare the columnstore index
There are several T-SQL query types that you can run to see performance improvements. In step 2 in the T-SQL script, pay attention to this pair of queries. They differ only on one line:
FROM FactResellerSalesXL_PageCompressed a
FROM FactResellerSalesXL_CCI a
A clustered columnstore index is in the FactResellerSalesXL_CCI table.
The following T-SQL script excerpt prints statistics for IO and TIME for the query of each table.
/********************************************************************* Step 2 -- Overview -- Page Compressed BTree table v/s Columnstore table performance differences -- Enable actual Query Plan in order to see Plan differences when Executing */ -- Ensure Database is in 130 compatibility mode ALTER DATABASE AdventureworksLT SET compatibility_level = 130 GO -- Execute a typical query that joins the Fact Table with dimension tables -- Note this query will run on the Page Compressed table, Note down the time SET STATISTICS IO ON SET STATISTICS TIME ON GO SELECT c.Year ,e.ProductCategoryKey ,FirstName + ' ' + LastName AS FullName ,count(SalesOrderNumber) AS NumSales ,sum(SalesAmount) AS TotalSalesAmt ,Avg(SalesAmount) AS AvgSalesAmt ,count(DISTINCT SalesOrderNumber) AS NumOrders ,count(DISTINCT a.CustomerKey) AS CountCustomers FROM FactResellerSalesXL_PageCompressed a INNER JOIN DimProduct b ON b.ProductKey = a.ProductKey INNER JOIN DimCustomer d ON d.CustomerKey = a.CustomerKey Inner JOIN DimProductSubCategory e on e.ProductSubcategoryKey = b.ProductSubcategoryKey INNER JOIN DimDate c ON c.DateKey = a.OrderDateKey GROUP BY e.ProductCategoryKey,c.Year,d.CustomerKey,d.FirstName,d.LastName GO SET STATISTICS IO OFF SET STATISTICS TIME OFF GO -- This is the same Prior query on a table with a clustered columnstore index CCI -- The comparison numbers are even more dramatic the larger the table is (this is an 11 million row table only) SET STATISTICS IO ON SET STATISTICS TIME ON GO SELECT c.Year ,e.ProductCategoryKey ,FirstName + ' ' + LastName AS FullName ,count(SalesOrderNumber) AS NumSales ,sum(SalesAmount) AS TotalSalesAmt ,Avg(SalesAmount) AS AvgSalesAmt ,count(DISTINCT SalesOrderNumber) AS NumOrders ,count(DISTINCT a.CustomerKey) AS CountCustomers FROM FactResellerSalesXL_CCI a INNER JOIN DimProduct b ON b.ProductKey = a.ProductKey INNER JOIN DimCustomer d ON d.CustomerKey = a.CustomerKey Inner JOIN DimProductSubCategory e on e.ProductSubcategoryKey = b.ProductSubcategoryKey INNER JOIN DimDate c ON c.DateKey = a.OrderDateKey GROUP BY e.ProductCategoryKey,c.Year,d.CustomerKey,d.FirstName,d.LastName GO SET STATISTICS IO OFF SET STATISTICS TIME OFF GO
In a database with the P2 pricing tier, you can expect about nine times the performance gain for this query by using the clustered columnstore index compared with the traditional index. With P15, you can expect about 57 times the performance gain by using the columnstore index.
Monitor In-Memory OLTP storage for In-Memory OLTP
See Common Workload Patterns and Migration Considerations (which describes workload patterns where In-Memory OLTP commonly provides significant performance gains)