SQL Server 2016 – How to Migrate Tables with Foreign Keys to In-Memory OLTP

No, in-memory really is this unpolished. If you are familiar with Agile you will know the concept of "minimal shippable product"; in-memory is that. I get the feeling that MS needed a response to SAP's Hana and its ilk. This is what they could get debugged in the timeframe for a 2014 release.

As with anything else in-memory has costs and benefits associated with it. The major benefit is the throughput that can be achieved. One of the costs is the overhead for change management, as you mentioned. This doesn't make it a useless product, in my opinion, it just reduces the number of cases where it will provide net benefit. Just as columnstore indexes are now updatable and indexes can be filtered I have no doubt that the functionality of in-memory will improve over coming releases.

SQL Server 2016 is now generally available. Just as I supposed, In-Memory OLTP has received a number of enhancements. Most of the changes implement functionality that traditional tables have enjoyed for some time. My guess is that future features will be released at the same time for both in-memory and traditional tables. Temporal tables is a case-in-point. New in this version it is supported by both In-Memory and disk-based tables.

Parallel Execution:

SQL Server does support parallel inserts into temp tables in SQL Server 2014 with the SELECT INTO syntax. In SQL Server 2016 parallel inserts are also supported into temp tables that are heaps. In SQL Server 2016 SP1 parallel inserts into heaps require the TABLOCK hint.

A query that modifies table variables will not contain any parallel zones. However, a query that references a table variable may run in parallel.

Memory:

Yes, memory-based tables can only be in RAM and cannot spill to disk. See this article.

Performance Boost:

My advice would be to first measure the performance of your stored procedure to confirm that the temp tables are the source of the unacceptable performance. If you confirm that consider the following simpler options first:

• Only save data to temp tables that you need. Apply filters when inserting data as soon as possible.

• Create columns with the right data types.

• Create indexes as appropriate for your temp tables.

• Drop your temp tables as soon as you no longer need them.

• Make sure that your tempdb database follows best practices. This could be a separate post but here's one resource.

If none of that works and you feel confident that you understand the limits of memory optimized table variables go ahead and test your procedures with them. The previously referenced blog post does mention that as a use case:

As replacement for traditional table variables, and in some cases for #temp tables that are local to a stored procedure. This is particularly useful if there is a lot of tempdb contention in the system.