SQL Server 2016 requires following conditions to be met for parallel insert on CCI
- Must specify TABLOCK
- No NCI on the clustered columnstore index
- No identity column
- Database compatibility is set to 130
While these restrictions are enforced in SQL Server 2016 but they represent important scenarios. We are looking into relaxing these in subsequent releases. Another interesting point is that you can also load into ‘rowstore HEAP’ in parallel as well.
The restriction I’d most like to see reduced would be the “no non-clustered indexes” part. The rest seem forgivable for most clustered columnstore setups (i.e., fact tables).