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SQL Server In-Memory OLTP


In-Memory OLTP comes with Microsoft SQL Server 2014 and can significantly improve OLTP database application performance. It is a memory-optimized database engine integrated into the standard SQL Server engine. This system provides memory-optimized tables which are fully transactional and are accessed using class Translact-SQL instructions.

In-Memory Tables comes with some limitations. We won’t enumerate all but only those which are related to CodeFluent Entities:

  1. Foreign keys aren’t supported
  2. RowVersion and Timestamp columns aren’t supported: http://msdn.microsoft.com/en-us/library/dn133179.aspx
  3. Default constraints aren’t supported
  4. Some Transact-SQL constructs aren’t supported: http://msdn.microsoft.com/en-us/library/dn246937.aspx

Let’s handle those four points!

Foreign Keys

There are two options:

  • Don’t create relation 😦
  • Create relation without foreign key 🙂

The second solution requires the usage of an Aspect. Fortunately we already wrote it a few time ago: http://www.softfluent.com/forums/codefluent-entities/how-to-disable-creating-foreign-key-by-sql-producer-

Even if foreign keys do not exist anymore, CodeFluent Entities still generates LoadBy_Relation methods so you won’t see any difference in your code. 🙂

Foreign Keys

RowVersion

RowVersion is not supported by In Memory tables so let’s remove it. We have to set “Concurrency Mode” to “None”:

RowVersion

 

Default Constraints

Default constraints used by tracking columns (creation time & last write time) are not supported. Here we have two options:

  • Remove default constraints 😦
  • Move them into the Save stored procedure 🙂

The first option is available in the Property Grid at project or entity level by removing the tracking time columns:

Properties

The second option can be done with an Aspect as you can see in the full example (see below). The edited INSERT statement looks like:

    INSERT INTO [Customer] (
        [Customer].[Customer_Id],
        [Customer].[Customer_Name],
        [Customer].[Customer_ContactSource_Id],
        [Customer].[_trackCreationUser],
        [Customer].[_trackLastWriteUser],
        [Customer].[_trackLastWriteTime])
    VALUES (
        @Customer_Id,
        @Customer_Name,
        @Customer_ContactSource_Id,
        @_trackLastWriteUser,
        @_trackLastWriteUser,
        (GETDATE())) -- Default Value

Tansact SQL

By default the SQL Server Producer surround the procedure code with a transaction. This transaction isn’t supported when using In Memory Table. The following exception is thrown when calling the stored procedure:

Unhandled Exception: System.Data.SqlClient.SqlException: Accessing memory optimized tables using the READ COMMITTED isolation level is supported only for autocommit transactions. It is not supported for explicit or implicit transactions. Provide a supported isolation level for the memory optimized table using a table hint, such as WITH (SNAPSHOT).

To remove it, we have to configure the SQL Server to not produce it:

SQL Server

 

Migrate the table

After those small changes, we can migrate the table to an In Memory table:

Migration

Migration Result

 

We can now use the In Memory table from the application:

Customer customer = new Customer();
customer.Name = "John Doe";
customer.Save();

All-in-One method

All the previous steps are automated by an aspect. All you have to do is include the aspect and set “enabled” on tables:

SqlServer In Memory Aspect

The full code sample including the aspect is available on our GitHub repository.

The R&D Team

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