Assume that you use SQL Server 2017. You will notice that ALTER INDEX REORGANIZE skips over the rowgroup with DICTIONARY_SIZE, regardless of how many deleted rows exist in therowgroup. When you do a merge operation, this improvement will increase the index efficiency by using a thresholdthat is the number of deleted rows in the rowgroup.
This improvement is included in the following cumulative update 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: