使用LINQ子查询填充子集合属性

Question

对于LINQ来说，我相当新，但我已经设法弄清楚了目前为止得到我想要的结果。下面的LINQ2SQL查询产生期望的结果，其中有位置对象，每个位置对象都有它们自己的单位集合。初始变量声明是为了设置我需要查询的值而设置的，并且不应与我的问题相关，但是需要用于上下文。

我遇到的问题是，有400多个位置，目前我有查询结构的方式，它是击中每个数据库而不是一个大查询。这导致性能受到很大的影响，需要30多秒才能使整个结果回来，这是不可接受的。我有一个存储过程SQL查询，只返回一两秒钟的结果。

有没有一种方法来重组这个查询，以便我没有击中每个位置的数据库？我确定它是由Units子查询中额外的“ToList（）”引起的，但我不知道如何在没有ToList（）的情况下对结果进行形状修改。任何性能调整将是一个巨大的帮助。谢谢你的帮助！

Dim curNames1 = (From ons In dc.organization_names _ 
    Where ons.eff_date <= ssDate _ 
    Order By ons.eff_date Descending _ 
    Group ons By ons.organization_id Into gNames = Group _ 
    Select New With { _ 
    Key .Key = organization_id, _ 
    .Result = gNames.Take(1)}) _ 
    .SelectMany(Function(a) (a.Result)) 

Dim curLocs1 = (From oLocs In dc.organization_locations _ 
    Where oLocs.eff_date <= ssDate _ 
    Order By oLocs.eff_date Descending _ 
    Group oLocs By oLocs.organization_id Into gLocs = Group _ 
    Select New With { _ 
    Key .Key = organization_id, _ 
    Result = gLocs.Take(1)}) _ 
    .SelectMany(Function(a) (a.Result)) 

Dim curStatuses1 = (From oEDate In dc.organization_conversion_dates _ 
    Where oEDate.edate <= ssDate _ 
    Order By oEDate.edate Descending _ 
    Group oEDate By oEDate.organization_id Into gEDates = Group _ 
    Select New With { _ 
    Key .Key = organization_id, _ 
    .Result = gEDates.Take(1)}) _ 
    .SelectMany(Function(a) (a.Result)) 

Dim curCommand1 = (From oCommand In dc.organization_service_assigneds _ 
    Where oCommand.eff_date <= ssDate _ 
    Order By oCommand.eff_date Descending _ 
    Group oCommand By oCommand.organization_id Into gCmds = Group _ 
    Select New With { _ 
    Key .Key = organization_id, _ 
    .Result = gCmds.Take(1)}) _ 
    .SelectMany(Function(a) (a.Result)) 

Dim curComponent1 = (From oCompo In dc.organization_compos _ 
    Where oCompo.eff_date <= ssDate _ 
    Order By oCompo.eff_date Descending _ 
    Group oCompo By oCompo.organization_id Into gCompos = Group _ 
    Select New With { _ 
    Key .Key = organization_id, _ 
    .Result = gCompos.Take(1)}) _ 
    .SelectMany(Function(a) (a.Result)) 

ss.Locations = New ObservableCollection(Of Location)((_ 
    From map In dc.MapBackgrounds Where map.MapID = options.Map _ 
    Let Locs = map.Schemes.SchemeLocations _ 
    From SchemeLoc In Locs _ 
    Where (options.Locations.Count = 0 Or _ 
     options.Locations.Contains(SchemeLoc.Location.ID)) _ 
    Select New Location With { _ 
    .ID = SchemeLoc.Location.ID, .Name = SchemeLoc.Location.Location, _ 
    .Y = SchemeLoc.Y, .X = SchemeLoc.X, _ 
    .Country = New Country With _ 
    {.ID = SchemeLoc.Location.Countries.ID, _ 
    .Name = SchemeLoc.Location.Countries.country}, _ 
    .State = If(SchemeLoc.Location.State = -1, Nothing, _ 
    New USState With {.ID = SchemeLoc.Location.States.ID, _ 
    .Name = SchemeLoc.Location.States.state, _ 
    .Abbreviation = SchemeLoc.Location.States.state}), _ 
    .Units = New ObservableCollection(Of MillitaryUnit)((_ 
    From curLoc In curLocs1 _ 
    Where curLoc.location = SchemeLoc.Location.ID _ 
    From curName In curNames1 _ 
    Where curName.organization_id = curLoc.organization_id _ 
    And (options.UnitSizes.Count = 0 Or _ 
     options.UnitSizes.Contains(curName.UnitSize)) _ 
    And (options.UnitTypes.Count = 0 Or _ 
    options.UnitTypes.Contains(curName.UnitType)) _ 
    From curEDate In curStatuses1 _ 
    Where curEDate.organization_id = curLoc.organization_id _ 
    And (options.Statuses.Count = 0 Or _ 
    options.Statuses.Contains(curEDate.status)) _ 
    From curCmd In curCommand1 _ 
    Where curCmd.organization_id = curLoc.organization_id _ 
    And (options.Commands.Count = 0 Or _ 
    options.Commands.Contains(curCmd.service_assigned)) _ 
    From curCompo In curComponent1 _ 
    Where curCompo.organization_id = curLoc.organization_id _ 
    And (options.Components.Count = 0 Or _ 
    options.Components.Contains(curCompo.compo)) _ 
    From curTable In curLoc.Organization.organization_tables _ 
    Where curTable.organization_id = curLoc.organization_id _ 
    And (options.Tables.Count = 0 Or _ 
    (options.Tables.Contains(curTable.table_id) Or _ 
    curTable.Tables.Any(Function(a) (options.Tables.Contains(a.parent_id))))) _ 
     Select New MillitaryUnit With { _ 
     .ID = curLoc.organization_id, _ 
     .Name = curName.name, _ 
     .IconPath = curName.icon, _ 
     .ConversionStatus = curEDate.Status1.status, _ 
     .ServiceCommand = curCmd.Service_Assigneds.service_assigned, _ 
     .Component = curCompo.Components.compo}).Distinct().ToList())}).ToList()) 

UPDATE（2009/3/3上午10点58）： 我设法使用下面的查询来获取数据传回在一个查询，但它是一个平坦的桌面结果。我怎样才能塑造这个组织，使得组织的东西在每个地点都变得层次分明？我相信我想使用“Group Join”之类的东西，但我并不熟悉它的工作原理。位置信息是直到“OrgID”列的所有信息。我需要将这些数据塑造成一系列位置，每个位置都有一个“单位”属性，该属性是位于该位置的组织的集合。任何指导？

Dim locationsquery = (From map In dc.MapBackgrounds Where map.MapID = 1 Let Locs = map.Schemes.SchemeLocations _ 
        From SchemeLoc In Locs Join curLoc In curLocs1 On SchemeLoc.LocID Equals curLoc.location _ 
        Join curName In curNames1 On curLoc.organization_id Equals curName.organization_id _ 
        Join curStatus In curStatuses1 On curLoc.organization_id Equals curStatus.organization_id _ 
        Join curCommand In curCommand1 On curLoc.organization_id Equals curCommand.organization_id _ 
        Join curComponent In curComponent1 On curLoc.organization_id Equals curComponent.organization_id _ 
        Select New With {.LocationID = SchemeLoc.LocID, .X = SchemeLoc.X, .Y = SchemeLoc.Y, _ 
             .LocationName = SchemeLoc.Location.Location, _ 
             .CountryID = SchemeLoc.Location.Countries.id, .CountryName = SchemeLoc.Location.Countries.country, _ 
             .StateID = SchemeLoc.Location.State, .StateName = SchemeLoc.Location.States.state, .StateAbbrev = SchemeLoc.Location.States.state, _ 
             .OrgID = curLoc.organization_id, _ 
             .OrgName = curName.name, _ 
             .OrgLocID = curLoc.location, _ 
             .IconPath = curName.icon, _ 
             .ConversionStatus = curStatus.status1.status, _ 
             .CurCmd = curCommand.service_assigneds.service_assigned, _ 
             .CurCompo = curComponent.components.compo}) 

Answer 1

所以我结束了重做的事情，并与下面的解决方案只查询数据库两次，更快想出了：

Dim locationsOnly = (From map In dc.MapBackgrounds Where map.MapID = 1 Let Locs = map.Schemes.SchemeLocations _ 
            From SchemeLoc In Locs _ 
            Where (options.Locations.Count = 0 Or options.Locations.Contains(SchemeLoc.LocID)) _ 
            Select New With {.LocationID = SchemeLoc.LocID, .X = SchemeLoc.X, .Y = SchemeLoc.Y, _ 
             .LocationName = SchemeLoc.Location.Location, _ 
             .CountryID = SchemeLoc.Location.Countries.ID, .CountryName = SchemeLoc.Location.Countries.country, _ 
             .StateID = SchemeLoc.Location.State, .StateName = SchemeLoc.Location.States.state, .StateAbbrev = SchemeLoc.Location.States.state}).ToList() 


Dim orgsOnly = (From curLoc In curLocs1 _ 
        Join curName In curNames1 On curLoc.organization_id Equals curName.organization_id _ 
        Join curStatus In curStatuses1 On curLoc.organization_id Equals curStatus.organization_id _ 
        Join curCommand In curCommand1 On curLoc.organization_id Equals curCommand.organization_id _ 
        Join curComponent In curComponent1 On curLoc.organization_id Equals curComponent.organization_id _ 
        Join curTable In dc.organization_tables On curLoc.organization_id Equals curTable.organization_id _ 
        Where (options.UnitSizes.Count = 0 Or options.UnitSizes.Contains(curName.UnitSize)) _ 
         And (options.UnitTypes.Count = 0 Or options.UnitTypes.Contains(curName.UnitType)) _ 
         And (options.Statuses.Count = 0 Or options.Statuses.Contains(curStatus.status)) _ 
         And (options.Commands.Count = 0 Or options.Commands.Contains(curCommand.service_assigned)) _ 
         And (options.Components.Count = 0 Or options.Components.Contains(curComponent.compo)) _ 
         And (options.Tables.Count = 0 Or (options.Tables.Contains(curTable.table_id) Or curTable.Tables.Any(Function(a) (options.Tables.Contains(a.parent_id))))) _ 
        Select New With {.OrgLocID = curLoc.location, _ 
         .MilUnit = New MillitaryUnit With { _ 
         .ID = curLoc.organization_id, _ 
         .Name = curName.name, _ 
         .IconPath = curName.icon, _ 
         .ConversionStatus = curStatus.Status1.status, _ 
         .ServiceCommand = curCommand.Service_Assigneds.service_assigned, _ 
         .Component = curComponent.Components.compo}}).Distinct().ToList() 


ss.Locations = New System.Collections.ObjectModel.ObservableCollection(Of Location)((From loc In locationsOnly _ 
        Group Join org In orgsOnly On loc.LocationID Equals org.OrgLocID Into Orgs = Group _ 
        Select New Location With { _ 
         .ID = loc.LocationID, _ 
         .Name = loc.LocationName, _ 
         .X = loc.X, _ 
         .Y = loc.Y, _ 
         .Country = New Country With {.ID = loc.CountryID, .Name = loc.CountryName}, _ 
         .State = New USState With {.ID = loc.StateID, .Name = loc.StateName, .Abbreviation = loc.StateAbbrev}, _ 
         .Units = New System.Collections.ObjectModel.ObservableCollection(Of MillitaryUnit)((From curOrg In Orgs _ 
          Select curOrg.MilUnit).ToList())}).ToList()) 

感谢您的帮助casperOne！

Answer 2

代替构件暴露作为List<T>的，更改属性类型到IEnumerable<T>或IQueryable<T>。然后，您可以删除对ToList的呼叫，并且您的查询应该能够在服务器上一次性完成执行。

另外，这种代码是LINQ to SQL开始崩溃的地方，IMO。我认为如果你有一个存储过程可以给你想要的结果，那么你应该使用它，并且让LINQ to SQL处理返回数据到你的对象的映射。