How Can EF 6 Interception Mitigate Parameter Sniffing Performance Issues?

Parametric Sniffing in EF 6 Revisited

While dynamic queries offer flexibility, their size can lead to performance issues in EF 6. A common culprit is parameter sniffing, where the query plan is cached based on the initial execution parameters, leading to inefficient plans when parameters vary.

Addressing Parameter Sniffing with EF 6

To surmount parameter sniffing, it is crucial to inform the database engine to recomplile the query with each execution. While updating database statistics is standard practice, it may not fully address the issue.

Incorporating "OPTION RECOMPILE" with EF 6

Fortunately, EF 6 provides mechanisms to manipulate SQL commands before execution. One such technique involves using the interception feature.

Implementation via Interception

The following code sample illustrates the implementation of the OptionRecompileHintDbCommandInterceptor class:

public class OptionRecompileHintDbCommandInterceptor : IDbCommandInterceptor
{
    ...

    private static void addQueryHint(IDbCommand command)
    {
        ...
    }
}

This interceptor adds the OPTION RECOMPILE hint to SQL statements that begin with "select" and do not already contain the hint.

Usage

To leverage this interceptor, simply add the following code at the application startup:

DbInterception.Add(new OptionRecompileHintDbCommandInterceptor());

By utilizing this approach, you can force the database engine to recompile the query on each execution, mitigating parameter sniffing and improving query performance.

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