Contents
How do you overcome parameter sniffing?
Workarounds for SQL Server Parameter Sniffing
- Create SQL Server Stored Procedures using the WITH RECOMPILE Option.
- Use the SQL Server Hint OPTION (RECOMPILE)
- Use the SQL Server Hint OPTION (OPTIMIZE FOR)
- Use Dummy Variables on SQL Server Stored Procedures.
- Disable SQL Server Parameter Sniffing at the Instance Level.
What causes parameter sniffing?
While this feature is almost always good, there are times it can cause unexpected performance problems. This primarily occurs when the set of parameters that the execution plan was optimized for ends up being drastically different than the parameters that are being passed in right now.
What is bad parameter sniffing?
Parameter sniffing is only bad when your data values are unevenly distributed and cached query plans are not optimal for all values. When a stored procedure executes efficiently sometimes, but inefficiently at other, and you swear nothing else in the environment is changing, that’s often a case of parameter sniffing.
What is parameter sniffing in SSRS?
Parameter sniffing is the process whereby SQL Server creates an optimal plan for a stored procedure by using the calling parameters that are passed the first time a stored procedure is executed. The important point for us is that those parameters passed are used to determine how SQL Server will process the query.
What is Concat_null_yields_null?
When SET CONCAT_NULL_YIELDS_NULL is ON, concatenating a null value with a string yields a NULL result. For example, SELECT ‘abc’ + NULL yields NULL . When SET CONCAT_NULL_YIELDS_NULL is OFF, concatenating a null value with a string yields the string itself (the null value is treated as an empty string).
What is primary key clustered?
A clustered index defines the order in which data is physically stored in a table. In SQL Server, the primary key constraint automatically creates a clustered index on that particular column.
What is option recompile?
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.