LINQ实体建立多层子查询的更有效方法

Question

I am using the EF linq to entities. I need to get multiple layers of items for filling an treeview. The code below is really slow and takes a long time to load. The query generated by the EF is like 200 lines (checked this with SQL Profiler).

I was wondering if there is an more efficient way of doing this, maybe with multiple queries or code reordering. The performance is not really accaptable this way.

DBContext db = _DbProvider.GetContext();
List<Level1TreeviewRegion> treeList = (
    from level1Item in db.Level1Table
     join customer in db.Clients on level1Item.Customer_ID equals customer.Customer_ID
     let rentableLocations = (from level4 in db.Location where level4.Rentable_Unit == "J" && level1Item.Customer_ID == level4.Customer_ID && level1Item.Level1_Id == level4.Level1_Id select level4).FirstOrDefault()
     orderby customer.Treeview_sort_level_1_by == "n" ? level1Item.Name : "", customer.Treeview_sort_level_1_by != "n" ? level1Item.Level1_Id : 0
     where level1Item.Customer_ID == customerAreaId && rentableLocations != null
     select new Level1TreeviewRegion
     {
         Record_Number = level1Item.Record_Number,
         LEVEL1_ID = level1Item.Level1_Id,
         LEVEL1_NAME_WithoutCodes = !string.IsNullOrEmpty(level1Item.Name) ? level1Item.Name.Trim() : "",
         LEVEL1_NAME_WithCodes = !string.IsNullOrEmpty(level1Item.Name) ? level1Item.Level1_Id + "-" + level1Item.Name.Trim() : "",
         SearchString = !string.IsNullOrEmpty(level1Item.Name) ? level1Item.Level1_Id + level1Item.Name.Trim() : "",
         Level2List = (from level2 in db.Level2Table
                     let rentableLocations1 = (from level4 in db.Location where level4.Rentable_Unit == "J" && level2.KP_PERSNEEL == level4.Customer_ID && level2.Level1_Id == level4.Level1_Id && level2.Level2_Id == level4.Level2_Id select level4).FirstOrDefault()
                     orderby customer.Treeview_sort_level_2_by == "n" ? level2.Name : "", customer.Treeview_sort_level_2_by != "n" ? level2.Level2_Id : ""
                     where level2.KP_PERSNEEL == customerAreaId && level2.Level1_Id == level1Item.Level1_Id && rentableLocations1 != null
                     select new Level2TreeviewRegion
                     {
                         Record_Number = level2.Record_Number,
                         LEVEL2_CODE = level2.Level2_Id.Trim(),
                         LEVEL2_NAME_WithoutCodes = !string.IsNullOrEmpty(level2.Name) ? level2.Name.Trim() : "",
                         LEVEL2_NAME_WithCodes = !string.IsNullOrEmpty(level2.Name) ? level2.Level2_Id.Trim() + "-" + level2.Name.Trim() : "",
                         SearchString = !string.IsNullOrEmpty(level2.Name) ? level2.Level2_Id.Trim() + level2.Name.Trim() : "",
                         LEVEL1_ID = level2.Level1_Id,
                         Level3List = (from level3 in db.Level3Table
                                          let rentableLocations2 = (from level4 in db.Location where level4.Rentable_Unit == "J" && level3.Customer_ID == level4.Customer_ID && level3.Level1_Id == level4.Level1_Id && level3.Level2_Id == level4.Level2_Id && level3.Level3_Id == level4.Level3_Id select level4).FirstOrDefault()
                                          let objectsInObjectModule = (from om in db.Object_Module where om.Customer_ID == level2.KP_PERSNEEL && om.Level2_Id == level2.Level2_Id && om.Level1_Id == level2.Level1_Id && om.ModuleId == WishModules.VB2.ToString() select om.Level3_Id)
                                          orderby customer.Treeview_sort_level_3_by == "n" ? level3.Name : "", customer.Treeview_sort_level_3_by != "n" ? level3.Level3_Id : ""
                                          where (level3.Level2_Id.Trim() == level2.Level2_Id.Trim() && level3.Customer_ID == customerAreaId
                                                 // extra check with the LEVEL3_MODULE table, it was Object.MJP = J, now it needs a record in the LEVEL3_MODULE table
                                                 //so if no objects are found, it is good (all are visible) OR objects are found, only they are visible
                                                 && (!objectsInObjectModule.Any() || objectsInObjectModule.Contains(level3.Level3_Id)) && rentableLocations2 != null)
                                          select new Level3TreeviewRegion
                                          {
                                              Record_Number = level3.Record_Number,
                                              LEVEL1_ID = level3.Level1_Id,
                                              LEVEL2_CODE = level3.Level2_Id.Trim(),
                                              LEVEL3_CODE = level3.Level3_Id.Trim(),
                                              LEVEL3_NAME_WithoutCodes = !string.IsNullOrEmpty(level3.Name) ? level3.Name.Trim() : "",
                                              LEVEL3_NAME_WithCodes = !string.IsNullOrEmpty(level3.Name) ? level3.Level3_Id.Trim() + "-" + level3.Name.Trim() : "",
                                              SearchString = !string.IsNullOrEmpty(level3.Name) ? level3.Level3_Id.Trim() + level3.Name.Trim() : "",
                                              LEVEL3_PLAATS = level3.City.Trim(),
                                              Ownership = string.IsNullOrEmpty(level3.Ownership) == false && (new[] { "j", "ja", "y", "yes" }).Contains(level3.Ownership.ToLower().Trim()),
                                              Level4List = (from level4 in db.Level4Table
                                                              orderby customer.Treeview_sort_level_4_by == "n" ? level4.Description : "", customer.Treeview_sort_level_4_by != "n" ? level4.Code : ""
                                                              where level4.Rentable_Unit == "J" && level3.Level2_Id.Trim() == level4.Level2_Id.Trim() && level3.Customer_ID == level4.Customer_ID && level3.Level1_Id == level4.Level1_Id && level3.Level3_Id == level4.Level3_Id
                                                              select new Level4TreeviewRegion
                                                              {
                                                                  Record_Number = level4.Record_Number,
                                                                  LEVEL1_ID = level3.Level1_Id,
                                                                  LEVEL2_CODE = level3.Level2_Id.Trim(),
                                                                  LEVEL3_CODE = level3.Level3_Id.Trim(),
                                                                  LEVEL4_CODE = level4.Code.Trim(),
                                                                  LEVEL4_NAME_WithoutCodes = !string.IsNullOrEmpty(level4.Description) ? level4.Description.Trim() : "",
                                                                  LEVEL4_NAME_WithCodes = !string.IsNullOrEmpty(level4.Description) ? level4.Code.Trim() + "-" + level4.Description.Trim() : "",
                                                                  SearchString = !string.IsNullOrEmpty(level4.Description) ? level4.Code.Trim() + level4.Description.Trim() : "",
                                                              }).ToList()
                                          }).ToList()
                     }).ToList()
     }).ToList();

The relevant database part:

Level1Table
[RECNUM] [int] NOT NULL IDENTITY(1, 1),
[Level1_Id] [smallint] NOT NULL,

Level2Table
[RECNUM] [int] NOT NULL IDENTITY(1, 1),
[Level1_Id] [smallint] NOT NULL,
[Level2_Id] [char] (10),
[NAAM1] [char] (60),

Level3Table
[RECNUM] [int] NOT NULL IDENTITY(1, 1),
[Level1_Id] [smallint] NOT NULL,
[Level2_Id] [char] (10),
[Level3_Id] [char] (10),
[NAAM] [char] (60),

Level4Table
[RECNUM] [int] NOT NULL IDENTITY(1, 1),
[Level1_Id] [smallint] NOT NULL,
[Level2_Id] [char] (10) COLLATE,
[Level3_Id] [char] (10) COLLATE,
[Level4_Id] [char] (10) COLLATE,

Answer 1

Here are a few things you can do:

Move the logic of the property population into constructors:

public class Level1TreeviewRegion
{
    public Level1TreeviewRegion(Level1Item level1Item)
    {
        Record_Number = level1Item.Record_Number;
        LEVEL1_ID = level1Item.Level1_Id;
        LEVEL1_NAME_WithoutCodes = !string.IsNullOrEmpty(level1Item.Name) ? level1Item.Name.Trim() : "";
        LEVEL1_NAME_WithCodes = !string.IsNullOrEmpty(level1Item.Name) ? level1Item.Level1_Id + "-" + level1Item.Name.Trim() : "";
        SearchString = !string.IsNullOrEmpty(level1Item.Name) ? level1Item.Level1_Id + level1Item.Name.Trim() : "";
    }
    //...
}

Do this for all the Level[x]TreeViewRegion classes.

Turn rentablelocations into a count and use it on the where statement:

List<Level1TreeviewRegion> treeList = (
        from level1Item in db.Level1Table
        join customer in db.Clients on level1Item.Customer_ID equals customer.Customer_ID            
        orderby 
            customer.Treeview_sort_level_1_by == "n" ? level1Item.Name : "", 
            customer.Treeview_sort_level_1_by != "n" ? level1Item.Level1_Id : "0"
        where level1Item.Customer_ID == customerAreaId &&
        db.Location.Count(level4 =>
            level4.Rentable_Unit == "J" &&
            level1Item.Customer_ID == level4.Customer_ID &&
            level1Item.Level1_Id == level4.Level1_Id
        ) > 0

Do the same for rentableLocations1 and rentableLocations2 .

objectsInObjectModule does not need to be part of the level 3 subquery. It only uses stuff from level2 so you can move it up one level.

Remove the ToList() calls all over the place. You only need the last one.

The end result should be something along the lines of:

List<Level1TreeviewRegion> treeList = (
        from level1Item in db.Level1Table
        join customer in db.Clients on level1Item.Customer_ID equals customer.Customer_ID            
        orderby 
            customer.Treeview_sort_level_1_by == "n" ? level1Item.Name : "", 
            customer.Treeview_sort_level_1_by != "n" ? level1Item.Level1_Id : "0"
        where level1Item.Customer_ID == customerAreaId &&
        db.Location.Count(level4 =>
            level4.Rentable_Unit == "J" &&
            level1Item.Customer_ID == level4.Customer_ID &&
            level1Item.Level1_Id == level4.Level1_Id
        ) > 0
        select new Level1TreeviewRegion(level1Item)
        {
            Level2List = (from level2 in db.Level2Table                             
                          let objectsInObjectModule =
                            (
                                from om in db.Object_Module
                                where
                                    om.Customer_ID == level2.KP_PERSNEEL &&
                                    om.Level2_Id == level2.Level2_Id &&
                                    om.Level1_Id == level2.Level1_Id &&
                                    om.ModuleId == WishModules.VB2.ToString()
                                select om.Level3_Id
                            )
                          orderby customer.Treeview_sort_level_2_by == "n" ? level2.Name : "", customer.Treeview_sort_level_2_by != "n" ? level2.Level2_Id : ""
                          where 
                            level2.KP_PERSNEEL == customerAreaId && 
                            level2.Level1_Id == level1Item.Level1_Id && 
                            db.Location.Count(level4 =>
                                level4.Rentable_Unit == "J" &&
                                level2.KP_PERSNEEL == level4.Customer_ID &&
                                level2.Level1_Id == level4.Level1_Id &&
                                level2.Level2_Id == level4.Level2_Id
                            ) > 0
                          select new Level2TreeviewRegion(level2)
                          {
                              Level3List = (from level3 in db.Level3Table                                                                                                
                                            orderby 
                                                customer.Treeview_sort_level_3_by == "n" ? level3.Name : "", 
                                                customer.Treeview_sort_level_3_by != "n" ? level3.Level3_Id : ""
                                            where 
                                                (
                                                    level3.Level2_Id.Trim() == level2.Level2_Id.Trim() && 
                                                    level3.Customer_ID == customerAreaId
                                                   // extra check with the LEVEL3_MODULE table, it was Object.MJP = J, now it needs a record in the LEVEL3_MODULE table
                                                   //so if no objects are found, it is good (all are visible) OR objects are found, only they are visible
                                                   && (
                                                        !objectsInObjectModule.Any() || 
                                                        objectsInObjectModule.Contains(level3.Level3_Id)
                                                      ) 
                                                   && db.Location.Count(level4 =>
                                                    level4.Rentable_Unit == "J" &&
                                                    level3.Customer_ID == level4.Customer_ID &&
                                                    level3.Level1_Id == level4.Level1_Id &&
                                                    level3.Level2_Id == level4.Level2_Id &&
                                                    level3.Level3_Id == level4.Level3_Id) > 0
                                                )
                                            select new Level3TreeviewRegion(level3)
                                            {
                                                Level4List = (from level4 in db.Level4Table
                                                              orderby 
                                                              customer.Treeview_sort_level_4_by == "n" ? level4.Description : "", 
                                                              customer.Treeview_sort_level_4_by != "n" ? level4.Code : ""
                                                              where 
                                                                level4.Rentable_Unit == "J" && 
                                                                level3.Level2_Id.Trim() == level4.Level2_Id.Trim() && 
                                                                level3.Customer_ID == level4.Customer_ID && 
                                                                level3.Level1_Id == level4.Level1_Id && 
                                                                level3.Level3_Id == level4.Level3_Id
                                                              select new Level4TreeviewRegion(level4, level3))
                                            })
                          })
        }).ToList();

From past experience, when you end up with complex queries and logic that looks strikingly similar, it usually means you need to take a step back and rethink your design.