为了优化方法,我查看代码的每一行以及每个生成的请求,以便消除其中的最大数量。我对以下部分有严重怀疑:
计划包含多个项目。一个项目包含多个活动。我首先加载所有活动以备将来使用。正如预期的那样,这会在"活动"表上生成"选择在何处"请求
var planningProjectIds = p.PlanningProjects.Select(x => x.PlanningProjectId).ToList();
var planningActivities = _db.PlanningActivities.Where(x => planningProjectIds.Contains(x.PlanningProjectId));
var planningActivitiesArr = planningActivities.ToLookup(x => x.PlanningProjectId);
这是第一次尝试。以下代码生成不需要的请求(在日志行 9b 和 10 之间)
foreach (PlanningProject pp in p.PlanningProjects)
{
// ...
sw.WriteLine("9");
pp.PlanningActivities = planningActivitiesArr[pp.PlanningProjectId].ToList();
sw.WriteLine("9b");
pp.PlanningActivities = pp.PlanningActivities.OrderBy(x => x.Position).ThenBy(x => x.PlanningActivityId).ToList();
sw.WriteLine("10");
// ...
}
这是第二次尝试。此代码不生成查询
foreach (PlanningProject pp in p.PlanningProjects)
{
// ...
sw.WriteLine("9");
pp.PlanningActivities = planningActivitiesArr[pp.PlanningProjectId]
.OrderBy(x => x.Position)
.ThenBy(x => x.PlanningActivityId)
.ToList();
sw.WriteLine("10");
// ...
}
你能告诉我原因吗?提前谢谢你;)
这是日志的摘录,我们可以看到额外的请求
9b
Opened connection at 06/07/2017 10:22:15 +02:00
SELECT
[Extent1].[PlanningActivityId] AS [PlanningActivityId],
[Extent1].[FriendlyName] AS [FriendlyName],
[Extent1].[PlanningProjectId] AS [PlanningProjectId],
[Extent1].[ActivityId] AS [ActivityId],
[Extent1].[ScheduleID] AS [ScheduleID],
[Extent1].[Position] AS [Position]
FROM [dbo].[PlanningActivities] AS [Extent1]
WHERE [Extent1].[PlanningProjectId] = @EntityKeyValue1
-- EntityKeyValue1: '847' (Type = Int32, IsNullable = false)
-- Executing at 06/07/2017 10:22:15 +02:00
-- Completed in 7 ms with result: SqlDataReader
Closed connection at 06/07/2017 10:22:15 +02:00
10
不要犹豫,告诉我我是否可以忘记有价值的细节来解决这个小问题:)
在您的第一个块中,pp
仍然连接到数据库上下文,因此将延迟加载PlanningActivities
。如果在单个查询中执行所有操作并使用Include
加载子实体,则可以获得更好的性能和更少的查询。例如:
var projects = _db.Plannings
.Where(pl => pl.PlanningId == 1234)
.PlanningProjects
.Include(pl => pl.PlanningProjects
.Select(pp => pp.PlanningActivities))
.ToList();
当你枚举p.PlanningProjects
时,你只会得到PlanningProject
实体作为局部变量pp
。
此时,它不会填充任何导航属性。
foreach (PlanningProject pp in p.PlanningProjects)
{
// ...
}
调用属性获取器为"9b"和"10"之间的PlanningProject
填充PlanningActivities
后,将查询数据库以获取这些规划活动:
sw.WriteLine("9b");
pp.PlanningActivities = pp.PlanningActivities.OrderBy(x => x.Position).ThenBy(x => x.PlanningActivityId).ToList();
sw.WriteLine("10");
因此,查询:
SELECT ....
FROM [dbo].[PlanningActivities] where [PlanningProjectId] = @EntityKeyValue1
@EntityKeyValue1
是pp
变量的PlanningProject.PlanningProjectId
。
如果不需要数据提取查询,请使用 include 一次加载所有数据。