But there are furtherĬomplications with dynamic SQL, and since the facts about stored procedures are confusing enough I have deferred the discussion on dynamic Submits SQL statements directly, most of what I say this chapter is still applicable. If your application does not use stored procedures, but In this chapter we will look at how SQL Server compiles a stored procedureĪnd uses the plan cache. How SQL Server Compiles a Stored Procedure ![]() I would however recommend that you use the most recent version of SSMS which you can download here. If you use a different version of SSMS and/or SQL Server you may see slightly different results. This article will notĪll screenshots and output in this article were collected with SSMS 18.8 against an instance of SQL Server running SQL 2019 CU8. Not explain the basics in depth, as my focus is a little beyond that point. Little at query plans and if you have some basic knowledge of indexes. Performance tuning, but it certainly helps if you have looked a You don't need to have any prior experience of This is not a beginner-level article, but I assume that the reader has a (I have modified the original version to replace legacy LOB types with MAX types.) This is a old demo database from Microsoft, which you find in the file Northwind.sql. Beware that to run these queries you need to have the server-level permissionįor the examples in this article, I use the Northwind sample database. The article includes several queries to inspect the plan cache. The essence of this article applies to all versions of SQL Server from SQL 2005 and on. Getting Query Plans and Parameters from a TraceĮxamples of How to Fix Parameter-Sniffing Issues Getting the Most Recent Actual Execution Plan Getting the Query Plans and Parameters Directly from the Plan Cache Getting the Query Plans and Parameters with Management Studio Getting Information to Solve Parameter Sniffing Problems Statement Recompile and Table Variables and Table-Valued Parameters ![]() Section with links to Microsoft white papers and similar documents in this area. In the last chapter I look at how you can use Query Store, a feature that was introduced in SQL 2016 for your troubleshooting. May experience differences in performance between SSMS and the application withĭynamic SQL. Is compiled and interacts with the plan cache and why there are more reasons you Next comes a chapter where I discuss how dynamic SQL – both real-world situations I have encountered and more generic ones – and possible solutions. In the second chapter I discuss some scenarios Performance problems where parameter sniffing is involved. This is followed by two chapters how to deal with To discuss a few situations where there are other reasons for the difference in I first make a short break from the theme of parameter sniffing To understand how to address that performance problem in your application, you Will understand how come the query runs so much faster in SSMS. Multiple entries for a procedure in the cache. I explain how SQL Server uses the cache, and why there may be Is and why it is part of the equation in the vast majority of these confusing I explain how SQL Server compiles a stored procedure, what parameter sniffing ![]() In this article, I will try to straighten out why you get this seemingly inconsistent behaviour. Of how SQL Server compiles queries and maintains its plan cache, it may seem so.įurthermore, there are some unfortunate combinations of different defaults inĭifferent environments. But if you don't have a good understanding Procedure to run it stand-alone only to find that it runs much faster – or much A similar mystery is when a developer has extracted a query in his stored They are inclined to think that SQL Server is all about Management Studio (SSMS) to analyse it, only to find that the They take the SQL batch from the application and run it in SQL Server They have identified a slow query or slow stored procedure When I read various forums about SQL Server, I frequently see questions from This article is also available in Russian, translated by Dima Piliugin. See here for font conventions used in this article. Slow in the Application, Fast in SSMS? Slow in the Application, Fast in SSMS?Īn SQL text by Erland Sommarskog, SQL Server MVP.
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