SQL查询枢轴太慢了

Question

我正在尝试改进SQL查询，并且在运行执行计划之后，我为主表创建了Index-Non-Clustered，现在花费的时间更少，但查询仍然很慢。

SELECT  
    *
FROM 
    (SELECT 
        i.CodigoInstalador as Code,
        e.Nombre,
        t.TipoOrden as OrderType,
        dbo.TotalValulaadic_codigoi(CodigoInstalador,@From,@To) as ValvulaAdic,
        dbo.TotalHechuraadic_codigoi(CodigoInstalador,@From,@To) as HechuraAdic
    FROM 
        Orden_Instalacion  i 
            LEFT JOIN Empleado e 
                on e.Codigo = i.CodigoInstalador
            LEFT JOIN Orden_Instalacion_Detalle d 
                on d.IdInstalacion = i.IdInstalacion 
            LEFT JOIN Orden_Tipo t 
                on t.IdTipoOrden = d.IdTipoOrden 
    WHERE  
        i.IdRegion = @idRegion AND 
        i.FechaInstalacion >= @FromAND 
        FechaInstalacion<=@To
        AND Ejecutado = 1
    ) AS ps
    PIVOT
    (
        COUNT (OrderType)
        FOR TipoOrden IN
        ( 
            [Instalacion medidor proporcionado por usuario]
            ,[Instalation 1/2'' MyCo]
            ,[Instalation valvula 3/4'' MyCo]
            ,[Instalation box]
        )
    ) AS pvt

是否存在替换枢轴以改善查询的方法或我可以做的其他事情？