1. How to Use Parameters Like a Pro
…and Boost Performance
Guy Glantser

2. A Few Words about Me…
Name: Guy Glantser Address: Blog: Podcast:
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3. Let’s Begin
with a Story…

4. What is Parameterization?
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5. Why is it So Important?
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6. When does it Become Problematic?
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7. How can we Deal with it?
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8. SELECT
ProductName ,
ProductCategory
FROM
Production.Product
WHERE
ProductID =
17;

9. 17; SELECT ProductName , ProductCategory FROM Production.Product WHERE
ProductID =
17;

10. 63; SELECT ProductName , ProductCategory FROM Production.Product WHERE
ProductID =
63;

11. @ProductID; SELECT ProductName , ProductCategory FROM
Production.Product
WHERE
ProductID =
@ProductID;

12. The “Customers by Country” Case Study
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13. The “Customers by Country” Case Study
SELECT
Id ,
Name ,
LastPurchaseDate
FROM
Marketing.Customers
WHERE
Country = N'IL';

14. Case Study
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15. Plan Caching
Query plans are cached in the plan cache in order to be reused and avoid the cost of recompiling the same queries again and again.
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16. Plan Caching

17. Plan Caching
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18. 7 Ways To Execute Your Query

19. 7 Ways…
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20. Parameter Sniffing
The query optimizer “sniffs” the parameter values during first execution, and optimizes the query based on these values.
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21. Parameter Sniffing
Local variables are not parameters, so the query optimizer has nothing to sniff. The values of local variables are only assigned at run-time.
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22. Parameter Sniffing Is Parameter Sniffing Good or Bad?
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23. Parameter Sniffing
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24. Parameter Sniffing
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25. Parameter Sniffing
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26. Parameter Sniffing
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27. Parameter Sniffing
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28. Non-Uniform Data Distribution
Possible Solutions:
sys.sp_recompile
WITH RECOMPILE
OPTION (RECOMPILE)
OPTION (OPTIMIZE FOR)
Multiple Stored Procedures
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29. Changing Parameter Values
The optimizer sniffs the parameter values at compile-time, so if you change the parameter values at run-time, the plan will not be suitable for the new values. @

30. Changing Parameter Values
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31. Simple vs. Forced Parameterization
In simple parameterization, the optimizer automatically parameterizes only simple plans, in which the parameter values have absolutely no effect on the plan chosen.
Simple

32. Simple vs. Forced Parameterization
In forced parameterization, the optimizer automatically parameterizes most plans.
Forced

33. Simple vs. Forced Parameterization
Parameterization can be applied at the:
Database Level
Query Template Level
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34. Simple vs. Forced
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35. Summary
Parameterization is a very important aspect of the query processor’s job when compiling and executing queries.
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36. Summary
Inappropriate handling of parameterization can lead to poor performance. Unfortunately, it is common to neglect this area.
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37. Summary
Tip #1
Usually, data distribution is more or less uniform, so, in general, prefer parameterized queries over non-parameterized queries.
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38. Summary
Tip #2
When data is not uniformly distributed, rewrite your code using one of the methods shown in this session.
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39. Summary
Tip #3
Avoid the use of local variables as an alternative for parameters.
Use parameters instead.
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40. Summary
Tip #4
Don’t change parameter values inside your stored procedures.
Pass the calculated values to inner stored procedures to use parameter sniffing or use OPTION (RECOMPILE).
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41. Summary
Tip #5
Force parameterization only when you have no other choice.
Prefer forced parameterization at the query template level.
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42. Back to the Story…

43. My Blog Series About Parameterization…
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44. Questions?
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45. Keep in Touch…
Name: Guy Glantser Address: Blog: Podcast:
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46. Image courtesy of David Castillo Dominici / FreeDigitalPhotos.net