Improvement
Assume that you use SQL Server 2016 or 2017. You will notice that ALTER INDEX REORGANIZE skips over the rowgroup with DICTIONARY_SIZE, regardless of how many deleted rows exist in the rowgroup. When you do a merge operation, this improvement will increase the index efficiency by using a threshold that is the number of deleted rows in the rowgroup.
Resolution
This improvement is included in the following cumulative updates for SQL Server:
About cumulative updates for SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:
References
Learn about the terminology that Microsoft uses to describe software updates.
