SQL Server 2019 :: does features apply to previous compatibility level?

Question

I have a SQL Server 2019 instance on my hands but all database in it are set to Compatibility Level 110 (SQL Server 2012).

I would like to rebuild a few indexes with the options:

ALTER INDEX ALL ON [MyIndexName] 
REBUILD WITH(FILLFACTOR = 80, 
                ONLINE = ON, 
                SORT_IN_TEMPDB = ON
                RESUMABLE = ON,
                OPTIMIZE_FOR_SEQUENTIAL_KEY = ON);

My question is, as RESUMABLE = ON and OPTIMIZE_FOR_SEQUENTIAL_KEY = ON are features introduced from SQL Server 2019 will they apply to my databases as well even if they are still on Compatibility Level 110?

Answer 1

The reply is: we cannot tell.

• “[…] New features may work under older compatibility levels but beware of SET options.” (https://learn.microsoft.com/en-us/archive/blogs/sqlserverstorageengine/whats-the-difference-between-database-version-and-database-compatibility-level )
• “[…]For pre-existing databases running at lower compatibility levels, as long as the application does not need to leverage enhancements that are only available in a higher database compatibility level, it is a valid approach to maintain the previous database compatibility level. For new development work, or when an existing application requires use of new features such as Intelligent Query Processing, as well as some new Transact-SQL, plan to upgrade the database compatibility level to the latest available. For more information, see Compatibility levels and Database Engine upgrades.” (https://learn.microsoft.com/en-us/sql/t-sql/statements/alter-database-transact-sql-compatibility-level?view=sql-server-ver15 )

I also asked to Randolph West on a post and the reply is: "Some features apply to the instance level, while some apply only to databases in the correct compatibility level. Optimize for sequential key is a 150-level feature."

So we just need to try out on a test environment as suggested in the comments above.