We are delighted to announce that Resumable Online Index Rebuild (ROIR) is now available for public preview in Azure SQL DB. With this feature, you can resume a paused index rebuild operation from where the rebuild operation was paused rather than having to restart the operation at the beginning. Additionally, this feature rebuilds indexes using only a small amount of log space. You can use the new feature in the following scenarios:
- Resume an index rebuild operation after an index rebuild failure (such as after a database failover or after running out of disk space).
- Pause an ongoing index rebuild operation and resume it later.
- Rebuild large indexes without using a lot of log space and have a long-running transaction that blocks other maintenance activities.

Read about it in the Azure blog.