SQL Server Execution Plans - Red Gate Software

Chapter 8: Advanced Topics
Examining a parallel execution plan
If you're performing these tests on a machine with a single processor, then you won't be
able to see any parallel plans. Kalen Delaney supplied a method for simulating multiple
processors in SQL Server Magazine, InstantDoc #95497 (available only to subscribers).
In the SQL Server Configuration Manager, right-click the appropriate SQL Server service
and edit the startup properties. Add a property "-Pn" which represents the number of
processors that you want to simulate. You must then restart the service. This simulates
parallel execution plans, but it does not actually give you parallel execution on a single
processor machine.
For more detail, read the article. However, I'll repeat the warning from the article: Never
do this on a production system.
We'll start with an aggregation query, of the sort that you might find in a data mart. If
the dataset this query operates against is very large, it might benefit from parallelism.
SELECT so.ProductID ,
COUNT(*) AS Order_Count
FROM Sales.SalesOrderDetail so
WHERE so.ModifiedDate >= '2003/02/01'
AND so.ModifiedDate < DATEADD(mm, 3, '2003/02/01')
GROUP BY so.ProductID
ORDER BY so.ProductID
Listing 8.5
Figure 8.4 shows the estimated execution plan, which seems straightforward.
Figure 8.4
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