SQL Server 2019 brings a very exciting new feature that, is long overdue. Resumable online index create is one of my favorite new things. This paired with the Resumable Index Rebuilds introduced with SQL Server 2017 really gives database administrators much more control over index processes.
Have you ever started to build a new index on very large table only to have users call and complain their process is hung, not completing, or system is slow? That’s when you realize you’re the cause because you tried to sneak in a new index. I have many times, because creating a new index can impact performance and can be a problematic process for users when you have no or little downtime windows available. When you kill the create process it rolls back requiring you to start from the beginning the next time. With resumable online index creation you now have the ability to pause and restart the build at the point it was paused. You can see where this can be very handy.
To use this option for creating the index you must include the RESUMABLE=ON
CREATE INDEX MyResumableIndex on MyTable (MyColumn) WITH (ONLINE=ON, RESUMABLE=ON, MAX_DURATION=30)
Let’s say you have only two 30-minute windows available to create this new index over the next two days. You could use the MAX_DURATION option with the new RESUMABLE=ON to specify the time interval for an index being built. Once the 30 minutes is up the index build automatically gets paused if it has not completed. When you’re ready the next day you can RESUME right where it left off allowing you to complete the process. Very cool.
Another added benefit is managing transaction log growth. As we all know, creating indexes especially large ones can cause hefty log growth events and can unfortunately lead to running out of disk space. This new functionality allows us to better manage that. We can now pause the process and truncate or backup the log mid process building the index in chunks.
In the case of when you create an index only to get complaints from users or manage your log growth you can simply do the below to PAUSE and restart it when a time is better, or your transaction log maintenance has completed.
You can KILL the SPID creating the index or run the below.
ALTER INDEX MyResumableIndex ON MyTable PAUSE;
To restart run the below or simply re-execute your CREATE INDEX statement
ALTER INDEX MyResumableIndex on MyTable RESUME
According to MSDN Resumable online index create supports the follow scenarios:
- Resume an index create operation after an index create failure, such as after a database fail over or after running out of disk space.
- Pause an ongoing index create operation and resume it later allowing to temporarily free system resources as required and resume this operation later.
- Create large indexes without using as much log space and a long-running transaction that blocks other maintenance activities and allowing log truncation.
*Note: SORT_IN_TEMPDB=ON is not supported when using RESUMABLE=ON
Once you pause it, how do you know how far the index got and how much is left to be created. With the Resumable REBUILD Index feature added in SQL Server 2017 we also got a new sys.index_resumable_operations system view. This view shows us the percentage complete, current state, start time, and last pause time.
I am very excited about this new Index Create feature I think this is a big WIN for SQL Server 2019.
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