What Are The Implications Of Using The `OPTION (RECOMPILE)` Query Hint Versus Enabling The ` PARAMETER SNIFFING` Option At The Database Level On The Performance And Plan Caching Behavior Of A Stored Procedure That Uses A Mix Of Auto-parameterized And Explicitly Declared Parameters In SQL Server 2019, Particularly When Dealing With Queries That Involve Complex Joins And Subqueries?

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The choice between using OPTION (RECOMPILE) and enabling PARAMETER SNIFFING at the database level in SQL Server 2019 for a stored procedure with mixed parameters and complex queries involves several considerations:

OPTION (RECOMPILE)

  • Plan Caching: No plan is cached; a new plan is generated each execution.
  • Performance: Ensures optimal plans for current parameters but incurs compilation overhead, which can be significant for complex queries.
  • Parameter Sensitivity: Highly sensitive, generating plans tailored to each parameter set, which is beneficial for varying parameters.

PARAMETER SNIFFING (Enabled)

  • Plan Caching: The initial parameters determine the cached plan, reused for subsequent executions.
  • Performance: Efficient if parameters are consistent but may degrade with varying parameters, leading to suboptimal plans.
  • Parameter Sensitivity: Optimizes for initial parameters, potentially causing issues with widely varying parameters.

Considerations

  • Complex Queries: RECOMPILE may be beneficial for complex joins and subqueries as it tailors plans to current parameters.
  • Parameter Variability: If parameters vary significantly, RECOMPILE ensures optimal plans. For stable parameters, PARAMETER SNIFFING may suffice.
  • Compilation Overhead: Frequent recompiles can increase CPU usage, which must be balanced against plan optimality.

Conclusion

For a stored procedure with varying parameters and complex queries, OPTION (RECOMPILE) is recommended to ensure optimal execution plans despite the overhead. If parameters are stable, enabling PARAMETER SNIFFING may offer better performance. The decision hinges on workload specifics, parameter variability, and system resources.