Linq编译查询和性能问题

Question

我有一些linq编译查询的性能问题。

using (var txn = new TransactionScope(TransactionScopeOption.Required, new TransactionOptions { IsolationLevel = System.Transactions.IsolationLevel.ReadUncommitted })) 
     { 
      DateTime dealcheck = new DateTime(1753, 2, 2); 

      Func<DealDataClassesDataContext, string, IQueryable<DealsDetails>> DD = 
      CompiledQuery.Compile<DealDataClassesDataContext, string, IQueryable<DealsDetails>> 

    ((DealDataClassesDataContext nw, string sCity) => 

     from D in nw.Deals 

     where D.Address == City && (D.DealTime >= DateTime.Now || D.DealTime == dealcheck) && PriceMax >= D.DealPrice && D.DealPrice >= PriceMin && DisCountMax >= D.SavingsRate && D.SavingsRate >= DiscountMin && (D.DealTime >= DateTime.Now.AddDays(TimeMin) && D.DealTime <= DateTime.Now.AddDays(TimeMax) || D.DealTime == dealcheck) 

     select new DealsDetails(
          lst, 
          D.DealId, 
          D.DealHeadline, 
          D.DealCategory, 
          D.BuyPrice, 
          D.DealPrice, 
          D.SavingsRate, 
          D.SavingAmount, 
          D.RelatedWebsite, 
          D.Address, 
          string.Empty, 
          D.DealImage, 
          string.Empty, 
          string.Empty, 
          D.Time, D.CurrentTime, D.DealTime, 
         D.Location, string.Empty, string.Empty, D.Latitude, D.Longitude, D.Islocal, D.VendorMail, D.MerchantInfo, D.Review, D.HowItWork, D.DealUrl 
         )); 

      string jString = ""; 

      //int a = q(DealDbContext1, "London").Count(); 

      using (DealDataClassesDataContext db = new DealDataClassesDataContext()) 
      { 
       IQueryable<DealsDetails> DDD = DD.Invoke(DealDbContext, "London"); 

       if (lstSite.Count > 0 && lstSite[0] != "AllDeals") 
       { 
        DDD = DDD.Where(D => D.RelatedWebsite.Split(',').Where(x => lstSite.Contains(x)).Any()); //.Where(row => row.Category.ToList().Where(x => lst.Contains(x)).Any()).ToList(); 
       } 
       if (lst.Count > 0) 
       { 
        DDD = DDD.Where(D => D.Categories.Split(',').Where(x => lst.Contains(x)).Any()); //.Where(row => row.Category.ToList().Where(x => lst.Contains(x)).Any()).ToList(); 
       } 
       if (sortby == "Time" && orderby == "Asc") 
       { 
        DDD = (from d in DDD orderby d.Time ascending select d).Skip((Page - 1) * PageSize).Take(PageSize); 
       } 
       else if (sortby == "Time" && orderby == "Desc") 
       { 
        DDD = (from d in DDD orderby d.Time descending select d).Skip((Page - 1) * PageSize).Take(PageSize); 
       } 
       else if (sortby == "Price" && orderby == "Asc") 
       { 
        DDD = (from d in DDD orderby d.DealPrice ascending select d).Skip((Page - 1) * PageSize).Take(PageSize); 
       } 
       else if (sortby == "Price" && orderby == "Desc") 
       { 
        DDD = (from d in DDD orderby d.DealPrice descending select d).Skip((Page - 1) * PageSize).Take(PageSize); 
       } 
       else if (sortby == "Percent" && orderby == "Asc") 
       { 
        DDD = (from d in DDD orderby d.SavingsRate ascending select d).Skip((Page - 1) * PageSize).Take(PageSize); 
       } 
       else if (sortby == "Percent" && orderby == "Desc") 
       { 
        DDD = (from d in DDD orderby d.SavingsRate descending select d).Skip((Page - 1) * PageSize).Take(PageSize); 
       } 
       else 
       { 
        DDD = DDD.Skip((Page - 1) * PageSize).Take(PageSize); 
       } 

       string Currency = "$"; 
       foreach (DealsDetails item in DDD) 
       { 
        //Creating Html String Here 
       } 

       return jString; 

我附上了我的整个代码，请检查一下这个问题是什么，它需要很长的时间才能回复20秒。

主要是foreach循环超过17秒。

请让我知道如何编译此查询。

在此先感谢。

Answer 1

除了预编译查询，你应该pre-generate the local query views