Question

我正在使用实体框架和linq来执行多个左外连接，但是通过实体框架运行查询需要3秒。

我使用了((System.Data.Objects.ObjectQuery)query).ToTraceString();并在管理工作室中测试了sql语句，并立即执行。

这是linq代码。

 var query = from Inventory in db.INVENTORies                        

                    join NewInventory in db.NEW_INVENTORY on Inventory.Barcode equals NewInventory.Barcode into lj_1                          
                    from q_NewInventory in lj_1.DefaultIfEmpty()
                    join Categories in db.Categorys on Inventory.CAT_ID equals Categories.CAT_ID into lj_2
                    from q_Categories in lj_2.DefaultIfEmpty()
                    join SCategories in db.StoneCategories on Inventory.TP_ID equals SCategories.TP_ID into lj_3
                    from q_SubCategory in lj_3.DefaultIfEmpty()
                    join qSupplier in db.Suppliers on Inventory.SUP_ID equals qSupplier.SUP_ID into lj_4
                    from q_Supplier in lj_4.DefaultIfEmpty()
                    join qStatus in db.Statuses on Inventory.ST_ID equals qStatus.ST_ID into lj_5
                    from q_Status in lj_5.DefaultIfEmpty()
                    join q_Locations in db.Locations on Inventory.LOC_ID equals q_Locations.LOC_ID into lj_7
                    from q_locations in lj_7.DefaultIfEmpty()
                    join q_Stone1 in db.Stones on Inventory.StoneID_1 equals q_Stone1.STONE_ID into lj_s1
                    from q_stone1 in lj_s1.DefaultIfEmpty()
                    join q_Stone2 in db.Stones on Inventory.StoneID_2 equals q_Stone2.STONE_ID into lj_s2
                    from q_stone2 in lj_s2.DefaultIfEmpty()
                    join q_Stone3 in db.Stones on Inventory.StoneID_3 equals q_Stone3.STONE_ID into lj_s3
                    from q_stone3 in lj_s3.DefaultIfEmpty()
                    join q_Stone4 in db.Stones on Inventory.StoneID_4 equals q_Stone4.STONE_ID into lj_s4
                    from q_stone4 in lj_s4.DefaultIfEmpty()
                    join q_Stone5 in db.Stones on Inventory.StoneID_5 equals q_Stone5.STONE_ID into lj_s5
                    from q_stone5 in lj_s5.DefaultIfEmpty()
                    join q_Stone6 in db.Stones on Inventory.StoneID_6 equals q_Stone6.STONE_ID into lj_s6
                    from q_stone6 in lj_s6.DefaultIfEmpty()
                    join q_Stone7 in db.Stones on Inventory.StoneID_7 equals q_Stone7.STONE_ID into lj_s7
                    from q_stone7 in lj_s7.DefaultIfEmpty()
                    join q_Stone8 in db.Stones on Inventory.StoneID_8 equals q_Stone8.STONE_ID into lj_s8
                    from q_stone8 in lj_s8.DefaultIfEmpty()
                    join qMasterInventory in db.MASTERINVENTORies on q_NewInventory.InvItemNo equals qMasterInventory.INVITEMNO into lj_6
                    from q_MasterInventory in lj_6.DefaultIfEmpty()
                    where Inventory.Barcode == _Barcode

                    select new 
                    { 
                        inv_InvID = Inventory.INV_ID, inv_Barcode = Inventory.Barcode,
                        inv_catID = Inventory.CAT_ID, inv_SubCatID = Inventory.TP_ID, inv_Price = Inventory.ITEM_PRICE, inv_Cost = Inventory.ITEM_COST,
                        inv_PricePoint = Inventory.PricePoint, inv_StatusID = Inventory.ST_ID, inv_StID = Inventory.ST_ID, inv_SupID = Inventory.SUP_ID,
                        inv_LocID = Inventory.LOC_ID, inv_LabSupplier = Inventory.LabSupplier, inv_LabStone1 = Inventory.LabStone1, inv_LabCategory = Inventory.LabCategory,
                        inv_LabExtra = Inventory.LabExtra, inv_LabMadeIn = Inventory.LabMadeIn, inv_Width = Inventory.ChainThickNess, inv_Size = Inventory.ChainSize,
                        inv_Stone1 = Inventory.StoneID_1,inv_Stone2 = Inventory.StoneID_2,inv_Stone3 = Inventory.StoneID_3,inv_Stone4 = Inventory.StoneID_4,inv_Stone5 = Inventory.StoneID_5,inv_Stone6 = Inventory.StoneID_6,inv_Stone7 = Inventory.StoneID_7,inv_Stone8 = Inventory.StoneID_8,inv_Stone9 = Inventory.StoneID_9,inv_Stone10 = Inventory.StoneID_10,
                        stat_Status = q_Status.DESCRIPTION,
                        cat_Category = q_Categories.DESCRIPTION,
                        subCat_SubCategory = q_SubCategory.DESCRIPTION,
                        sup_Supplier = q_Supplier.Name,
                        loc_Location = q_locations.DESCRIPTION,

                        mas_SKU = q_MasterInventory.INVITEMNO,
                        mas_GUID = q_MasterInventory.ItemGUID,

                        stone1 = q_stone1.DESCRIPTION,
                        stone2 = q_stone2.DESCRIPTION,
                        stone3 = q_stone3.DESCRIPTION,
                        stone4 = q_stone4.DESCRIPTION,
                        stone5 = q_stone5.DESCRIPTION,
                        stone6 = q_stone6.DESCRIPTION,
                        stone7 = q_stone7.DESCRIPTION,
                        stone8 = q_stone8.DESCRIPTION,

                    };

Answer 1

为此查询创建数据库视图，并将视图映射到新的只读实体。之后比较纯LINQ执行和新执行之间的差异。如果问题是将可怕的LINQ查询转换为SQL，则可以通过使用此方法来避免它。如果它仍然很慢，问题将在其他地方。

Answer 2

评论中的家伙说你必须在T-SQL中重写它。真正。您可以尝试SQL to LINQ converter tools之一。
还可以使用MS SQL Profiler查看发生的情况并提高TSQL性能。
尝试添加索引but not too much：）

实体框架左外连接永远（性能问题）

2 个答案: