如何將OPTION重新添加到實體框架中

Question

我有時遇到parameter sniffing問題。 所以我想添加OPTION（RECOMPILE）到查詢的最後來修復它。 如何在EF 6中做到這一點？

Answer 1

我實現了IDbCommandInterceptor接口來修復參數嗅探錯誤。

新的攔截器的用法：

using (var dataContext = new AdventureWorks2012Entities()) 
    { 
    var optionRecompileInterceptor = new OptionRecompileInterceptor(); 
    DbInterception.Add(optionRecompileInterceptor); 

    string city = "Seattle"; 
    var seattle = (
     from a in dataContext.Addresses 
     where a.City == city 
     select a).ToList(); 

    DbInterception.Remove(optionRecompileInterceptor); //Remove interceptor to not affect other queries 
    } 

攔截器的執行情況：

public class OptionRecompileInterceptor : DbCommandInterceptor 
{ 
    static void AddOptionToCommand(DbCommand command) 
    { 
    string optionRecompileString = "\r\nOPTION (RECOMPILE)"; 
    if (!command.CommandText.Contains(optionRecompileString)) //Check the option is not added already 
    { 
     command.CommandText += optionRecompileString; 
    } 
    } 


    public override void NonQueryExecuting(
    DbCommand command, DbCommandInterceptionContext<int> interceptionContext) 
    { 
    AddOptionToCommand(command); 
    } 

    public override void ReaderExecuting(
    DbCommand command, DbCommandInterceptionContext<DbDataReader> interceptionContext) 
    { 
    AddOptionToCommand(command); 
    } 

    public override void ScalarExecuting(
    DbCommand command, DbCommandInterceptionContext<object> interceptionContext) 
    { 
    AddOptionToCommand(command); 
    } 
}