Assume that you have created a clustered columnstore index (CCI) on a table that has lots of data in Microsoft SQL Server 2014. After you execute an UPDATE or INSERT statement on the table, the sys.partitions system view does not match the actual row count. In this situation, you may encounter the following issues:
Updates to row count for CCI may be incorrect after you run an UPDATE statement.
Delta store is not closed and recreated during the INSERT INTO…SELECT statements.
Delta store may generate an incorrect row count after rollbacks.
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Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.