Analytics Optimization with Columnstore Indexes in Microsoft SQL Server by Unknown

Author:Unknown
Language: eng
Format: epub, pdf

Chapter 9 Delete anD UpDate OperatiOns

The rowgroup metadata can be seen in Figure 9-4.

Figure 9-4. Rowgroup metadata for a columnstore index, including deleted rows As is expected of a columnstore index that has had no delete operations executed against it, the deleted_rows column in sys.column_store_row_groups shows zero for each rowgroup. Executing the query in Listing 9-1 will delete a total of 15,400 rows from the columnstore index. Figure 9-5 shows the metadata details for the columnstore index after the deletion has completed.

Figure 9-5. Rowgroup metadata after a deletion has occurred

Each rowgroup now contains some number of deleted rows, depending on the

number of rows within them that happen to have been invoiced on 1/1/2016. Note that the total rows in each rowgroup and the size in bytes have not changed. This is expected and reflects the fact that rows were soft deleted via the delete bitmap.

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