Local Aggregation

Niko Neugebauer investigates a new line in the Columnstore Index Scan execution plan tooltip, Actual Number of Locally Aggregated Rows:

There is a new line in the properties of the iterator, showing the number of locally aggregated rows and that number equals 619255, that should be exactly the number of rows that is missing from the arrow connecting 2 iterators:

Gives us our perfect 12627608 rows.
Eureca!
Is there any more information on this operation?
Indeed, just right-click on the Columnstore Index Scan and select it’s properties:

This is tied to some columnstore performance improvements in SQL Server 2016.

Related Posts

Clustered Columnstore and Azure SQL DB

Arun Sirpal takes us through online clustered columnstore index creation in Azure SQL Database: What tier do you need to create one of these things? Let’s see. CREATE CLUSTERED  COLUMNSTORE INDEX cciSales ON [SalesLT].[ProductModelProductDescription] WITH ( ONLINE = ON ) But I get this message, Msg 40536, Level 16, State 32, Line 1‘COLUMNSTORE’ is not […]

Read More

Creating a Columnstore Index

Monica Rathbun shows a scenario where creating a clustered columnstore index can make data retrieval much faster: Using AdventureworksDW2016CTP3 we will work with the FactResellerSalesXL table which has 11.6 million rows in it. The simple query we will use as a demo just selects the ProductKey and returns some aggregations grouping them by the different […]

Read More

Categories

March 2016
MTWTFSS
« Feb Apr »
 123456
78910111213
14151617181920
21222324252627
28293031