为什么 EF 获取所有记录，然后通过 PK 再次获取所有记录

Question

我有以下 EF6 提取

       dgOrders.DataSource = Context.Orders
            .Where(o => o.ProposedOrder == ProposedOrders
                && o.Inactive == false
                && o.OnHold == false
                && o.Archive == false
                && (!o.ManufactureSiteFlag.HasValue || (o.ManufactureSiteFlag & currentSite) > 0)
                && (FilterOnDispatch == "" 
                    || (FilterOnDispatch.Equals("YES") && o.Deliveries.Count(d => d.Dispatched == true) > 0)
                    || (FilterOnDispatch.Equals("NO") && o.Deliveries.Count(d => d.Dispatched == false) > 0)));

当它执行时，它会在服务器上产生以下 SQL 序列

(@p__linq__0 bit,@p__linq__1 int,@p__linq__2 nvarchar(4000),@p__linq__3 nvarchar(4000),@p__linq__4 nvarchar(4000))
SELECT 
[Project3].[OrderID] AS [OrderID], 
[Project3].[OrderNum] AS [OrderNum], 
....
[Project3].[OrderDeliveryStatusID] AS [OrderDeliveryStatusID]
FROM ( SELECT 
    [Project2].[OrderID] AS [OrderID], 
    [Project2].[OrderNum] AS [OrderNum], 
    ....
    [Project2].[OrderDeliveryStatusID] AS [OrderDeliveryStatusID]
    FROM ( SELECT 
        [Project1].[OrderID] AS [OrderID], 
        [Project1].[OrderNum] AS [OrderNum], 
        ....
        [Project1].[OrderDeliveryStatusID] AS [OrderDeliveryStatusID], 
        [Project1].[C1] AS [C1], 
        (SELECT 
            COUNT(1) AS [A1]
            FROM [dbo].[Deliveries] AS [Extent3]
            WHERE ([Project1].[OrderID] = [Extent3].[OrderID]) AND (0 = [Extent3].[Dispatched])) AS [C2]
        FROM ( SELECT 
            [Extent1].[OrderID] AS [OrderID], 
            [Extent1].[OrderNum] AS [OrderNum], 
            ....
            [Extent1].[OrderDeliveryStatusID] AS [OrderDeliveryStatusID], 
            (SELECT 
                COUNT(1) AS [A1]
                FROM [dbo].[Deliveries] AS [Extent2]
                WHERE ([Extent1].[OrderID] = [Extent2].[OrderID]) AND (1 = [Extent2].[Dispatched])) AS [C1]
            FROM [dbo].[Orders] AS [Extent1]
        )  AS [Project1]
    )  AS [Project2]
    WHERE ([Project2].[ProposedOrder] = @p__linq__0) AND (0 = [Project2].[Inactive]) AND (0 = [Project2].[OnHold]) AND (0 = [Project2].[Archive]) AND (([Project2].[ManufactureSiteFlag] IS NULL) OR ((( CAST( [Project2].[ManufactureSiteFlag] AS int)) & (@p__linq__1)) > 0)) AND ((N'' = @p__linq__2) OR ((N'YES' = @p__linq__3) AND ([Project2].[C1] > 0)) OR ((N'NO' = @p__linq__4) AND ([Project2].[C2] > 0)))
)  AS [Project3]

然后生成

SELECT 
[Extent1].[OrderID] AS [OrderID], 
[Extent1].[OrderNum] AS [OrderNum], 
...
[Extent1].[OrderDeliveryStatusID] AS [OrderDeliveryStatusID]
FROM [dbo].[Orders] AS [Extent1];

SELECT 
[Extent1].[OrderID] AS [OrderID], 
[Extent1].[OrderNum] AS [OrderNum], 
....
[Extent1].[OrderDeliveryStatusID] AS [OrderDeliveryStatusID]
FROM [dbo].[Orders] AS [Extent1]
WHERE [Extent1].[OrderID] IN (91,181,421,690,844,1544,2460,2682,2687,2736,2760,2806,2816,2817,2818,3134,3141,3154,3473,3726,4404,4583,4590,4641,4673,4677,4695,4737,4741,4789,4837,4885,4886,4887,4889,4993,5013,5018,5043,5046,5074,5090,5106,5134,5141,5231,5260,5261,5264,5265,5276,5369,5371,5421,5458,5513,5583,5688,5837,5863,5894,5895,5908,6002,6055,6084,6113,6128,6240,6432,6589,6590,6651,6676,6708,6733,6757,6772,6785,6831,6931,6934,6935,6936,7003,7004,7043,7068,7128,7135,7170,7172,7195,7223,7243,7325,7350,7360,7377,7452,7504,7508,7568,7613,7614,7641,7676,7714,7740,7764,7842,8008,8023,8174,8244,8250,8269,8312,8340,8346,8392,8437,8470,8488,8652,8664,8703,8710,8722,8750,8831,8920,9016,9181,9243,9262,9413,9421,9429,9621,9680,9707,9709,9710,9772,9787,9797,9832,9911,9918,9959,9961,9972,10042,10052,10056,10083,10120,10189,10221,10222,10253,10254,10293,10348,10413,10415,10430,10442,10452,10468,10491,10505,10529,10555,10573,10630,10662,10787,10791,10804,10838,10887,10933,10934,10955,10968,11010,11020,11059,11072,11078,11149,11151,11188,11281,11299,11421,11496,11502,11572,11647,11655,11758,11817,11948,12049,12082,12137,12201,12275,12406,12451,12466,12472,12516,12547,12581,12608,12650,12666,12720,12730,12732,12771,12775,12792,12807,12810,12843,12965,13074,13075,13085,13087,13102,13153,13198,13316,13326,13516,13763,13795,13800,13802,13867,13871,13878,13887,13891);

第二个 SQL 语句使用不同的主键值重复多次。

为什么第一个select语句不足以满足请求的要求。随后的一组语句似乎返回了数据集的缩小视图，没有任何额外好处。

是否与交货的外键link有关？

如何提高性能？

UPDATE：除了采用下面的一些评论和答案来提高原始查询的性能外，额外的提取被追溯到 Context.Refresh 选项，出于某种原因是此行为的煽动者。

Answer 1

如果您使用参数来打开或关闭部分查询，您应该将其组合起来，而不是将其放入查询本身。这应该会简化查询本身。

var query = Context.Orders
        .Where(o => o.ProposedOrder == ProposedOrders
            && o.Inactive == false
            && o.OnHold == false
            && o.Archive == false
            && (!o.ManufactureSiteFlag.HasValue || (o.ManufactureSiteFlag & currentSite) > 0);

if (FilterOnDispatch.Equals("YES"))
    query = query.Where(o=>o.Deliveries.Count(d => d.Dispatched == true) > 0);
else if (FilterOnDispatch.Equals("NO"))
    query = query.Where(o=>o.Deliveries.Count(d => d.Dispatched == false) > 0);

dgOrders.DataSource = query;

此外，您是否在查询中包含任何实体？后续查询可能是由于 EF 必须将相关实体与主要实体放在一起。

为什么 EF 获取所有记录，然后通过 PK 再次获取所有记录

Why does EF fetch all records, then fetch all again by PK

c#

sql-server

entity-framework