how to use parameters like a pro …and boost performance guy glantser, ceo, madeira
TRANSCRIPT
How to Use Parameters Like a
Pro…and Boost Performance
Guy Glantser, CEO, Madeira
Name: Guy GlantserEmail Address: [email protected]: @guy_glantserBlog:
www.madeiradata.com/author/guyglantserPodcast: www.sqlserverradio.com
A Few Words about Me…
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Please silence cell phones
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Explore Everything PASS Has to Offer
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Let’s Beginwith a Story…
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What is Parameterization?
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Why is it So Important?
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When does it Become Problematic?
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How can we Deal with it?
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SELECTProductName ,ProductCategory
FROMProduction.Product
WHEREProductID = 17;
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SELECTProductName ,ProductCategory
FROMProduction.Product
WHEREProductID = 17;
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SELECTProductName ,ProductCategory
FROMProduction.Product
WHEREProductID = 63;
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SELECTProductName ,ProductCategory
FROMProduction.Product
WHEREProductID = @ProductID;
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The “Customers by Country” Case Study
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The “Customers by Country” Case Study
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SELECTId ,Name ,LastPurchaseDate
FROMMarketing.Customers
WHERECountry = N'IL';
Case StudyDemo
Plan Caching
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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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Plan Caching
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Plan CachingDemo
7 Ways…Demo
Parameter Sniffing
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The query optimizer “sniffs” the parameter values during first execution, and optimizes the query based on these values.
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Parameter Sniffing
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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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Parameter Sniffing
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Is Parameter SniffingGood or Bad?
Parameter Sniffing
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Parameter Sniffing
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Parameter Sniffing
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Parameter Sniffing
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Parameter SniffingDemo
Non-Uniform Data Distribution
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Possible Solutions:
• sys.sp_recompile
• WITH RECOMPILE
• OPTION (RECOMPILE)
• OPTION (OPTIMIZE FOR)
• Multiple Stored Procedures
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Changing Parameter Values
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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. @@
Changing Parameter ValuesDemo
Simple vs. Forced Parameterization
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In simple parameterization, the optimizer automatically parameterizes only simple plans, in which the parameter values have absolutely no effect on the plan chosen.
Simpl
e
Simple vs. Forced Parameterization
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In forced parameterization, the optimizer automatically parameterizes most plans.
Force
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Simple vs. Forced Parameterization
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Parameterization can be applied at the:
Database Level Query Template Level
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Simple vs. ForcedDemo
Summary
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Parameterization is a very important aspect of the query processor’s job when compiling and executing queries.
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Summary
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Inappropriate handling of parameterization can lead to poor performance.Unfortunately, it is common to neglect this area.
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Summary
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Tip #1Usually, data distribution is more or less uniform, so, in general, prefer parameterized queries over non-parameterized queries.
Summary
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Tip #2When data is not uniformly distributed, rewrite your code using one of the methods shown in this session.
Summary
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Tip #3Avoid the use of local variables as an alternative for parameters.Use parameters instead.
Summary
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Tip #4Don’t change parameter values inside your stored procedures.Pass the calculated values to inner stored procedures to use parameter sniffing.
Summary
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Tip #5Force parameterization only when you have no other choice.Prefer forced parameterization at the query template level.
Back to the Story…
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My Blog Series About Parameterization…
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http://www.madeiradata.com/tag/parameterization-s
eries/
Questions?
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Your feedback is important and valuable.
Name: Guy GlantserEmail Address: [email protected]: @guy_glantserBlog:
www.madeiradata.com/author/guyglantserPodcast: www.sqlserverradio.com
Keep in Touch…
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