What is parameter sniffing and how can it hurt performance?

Problem Statement

Explanation

With parameter sniffing, the first execution influences the cached plan. If that value is atypical, later executions may reuse a poor plan and run slowly. Mitigations include query hints or option recompile, separating skewed cases, or using plan guides and better statistics on skewed columns.

Code Solution

SolutionRead Only

-- SQL Server example
EXEC sp_executesql N'SELECT * FROM t WHERE status=@s', N'@s nvarchar(10)', @s='HOT';

Practice Sets

This question appears in the following practice sets:

Query Plans & Performance Tuning

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What is parameter sniffing and how can it hurt performance?

Problem Statement

Explanation

Code Solution

Practice Sets

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Master Interviews Anywhere, Anytime

What is parameter sniffing and how can it hurt performance?

Problem Statement

Explanation

Code Solution

Practice Sets

Related Questions

Which SQL statement retrieves all columns and rows from a table named employees?

Which clause filters rows before aggregation and affects which rows are grouped?

What is the default sort order when ORDER BY is used without ASC or DESC?

Which construct is commonly used to paginate results in SQL engines like Postgres and MySQL?

Which predicate correctly checks for missing values in standard SQL?

More from SQL & Databases

Master Interviews
Anywhere, Anytime