Parallel Loading Columnstore Indexes

Sunil Agarwal shows how to bulk load with parallelism into a clustered columnstore index from a staging table:

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).

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Wait Stats Related To Columnstore Indexes

Niko Neugebauer has some documentation on important wait stats around columnstore: I split the known wait types into the following distinct groups: – Batch Execution Mode (HTBUILD, HTDELETE, HTMEMO, HTREINIT, HTREPARTITION, PWAIT_QRY_BPMEMORY, BPSORT) – Columnstore Indexes (ROWGROUP_VERSION, ROWGROUP_OP_STATS, SHARED_DELTASTORE_CREATION, COLUMNSTORE_BUILD_THROTTLE, COLUMNSTORE_MIGRATION_BACKGROUND_TASK, COLUMNSTORE_COLUMNDATASET_SESSION_LIST) With an appearance in the next SQL Server version of the Batch Execution Mode for the RowStore […]

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Reserved Memory Allocation Waits And Trace Flag 834

Joe Obbish has another post looking at sub-optimal columnstore index performance: It is possible to see a scalability bottleneck in the form of high average wait time for the RESERVED_MEMORY_ALLOCATION_EXT wait if a highly concurrent workload is run on a server that consumes memory with batch mode operators. I believe that the severity of the bottleneck depends […]

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