How do I fix parameter sniffing in SQL Server?

Workarounds for SQL Server Parameter Sniffing

1. Create SQL Server Stored Procedures using the WITH RECOMPILE Option.
2. Use the SQL Server Hint OPTION (RECOMPILE)
3. Use the SQL Server Hint OPTION (OPTIMIZE FOR)
4. Use Dummy Variables on SQL Server Stored Procedures.
5. Disable SQL Server Parameter Sniffing at the Instance Level.

What is SQL Server parameter sniffing?

Parameter Sniffing is the process of looking to the first passed parameters values when compiling the stored procedure in order to create an optimal execution plan that fits these parameters values and use it for all values.

What is with recompile in SQL?

If a database undergoes significant changes to its data or structure, recompiling a procedure updates and optimizes the procedure’s query plan for those changes. When SQL Server executes procedures, any parameter values that are used by the procedure when it compiles are included as part of generating the query plan.

What causes parameter sniffing?

Something Smells Funny. And it’s not the elephant. SQL Server uses a process called parameter sniffing when it executes stored procedures that have – you guessed it – parameters. When the procedure is compiled or recompiled, the value passed into the parameter is evaluated and used to create an execution plan.

How do you identify a parameter sniffing?

The explicitness symptoms of parameter sniffing can be: The stored procedure performance execution performance shows inconsistency. It means that the procedure runs efficiently sometimes, but inefficiently at other times. Sudden degradation of procedure performance.

Can stored procedures be used as a security layer?

Stored Procedures can also act as an additional security layer. We pass data as a parameter in a Stored Procedure so SPs avoid SQL injection. We can also implement a security model on SPs rather than tables or views.

Should I disable parameter sniffing?

Now, do not think parameter sniffing is bad for your system, the matter of fact, it is enabled by the default shows that for most of the queries it is advantages. You should only disable it for certain queries with proper consultation.

What does Option recompile do?

OPTION(RECOMPILE) tells the server not to cache the pan for given query. This means that another execution of the same query will require to elaborate a new(maybe different) plan. This is used in the queries with parameters to prevent parameter sniffing issue.

What is parameter sniffing issue?

The problem with parameter sniffing is the fact that the first set of parameter values are used to determine the execution plan. To overcome this problem, all you need to do is to recompile the stored procedure every time it is executed.

What is parameter in SQL query?

Parameters are used to exchange data between stored procedures and functions and the application or tool that called the stored procedure or function: Input parameters allow the caller to pass a data value to the stored procedure or function. User-defined functions cannot specify output parameters.

Why would you need to use procedure Code when SQL is so powerful?

Reasons we need SQL Stored Procedures One reason is for maintainability. Also SQL stored procedures provide stronger security. They help assuage SQL injection attacks and they can also control what code a user can see. So if you have sensitive queries, you can avoid having users actually see the query code that is run.

How to optimize parameter sniffing in SQL Server?

A very underutilized technique indeed. This new database level enhancement was introduced recently which can help you overcome any issue with the parameter sniffing. The oldest and most traditional technique to not cache the query plans and compile your stored procedure or queries every single time to get optimal performance.

Is there a recompile option for parameter sniffing?

Today is the last blog post of the year 2019 and this is also a final blog post in the series of Parameter Sniffing which I have been writing. I strongly recommend that you read my earlier blog posts on this topic before you consider the option of recompile suggested in this blog post.

How to enable recompile in SQL Server management studio?

First, let us create a stored procedure that contains the keyword OPTION (RECOMPILE). Now enable the execution plan for your query window in SQL Server Management Studio (SSMS).

Is there parameter sniffing in T-SQL scalar functions?

Parameter sniffing occurs with T-SQL functions as well, though the way execution plans are generated can make this more difficult to see. There are good reasons to avoid T-SQL scalar and multi-statement functions in general, so for educational purposes only, here is a T-SQL multi-statement table-valued function version of our test query: