EntityFramework和EntityFramework.Extended使用說明——性能,語法和產生的sql

本文轉載自查看原文 2016-06-20 20:01 1371 ORM/ EntityFramework EntityFramework.Extended

環境說明:EntityFramework 6.1.3和.Net Framework4.5
性能注意事項:https://msdn.microsoft.com/zh-cn/library/cc853327.aspx
比較精髓的一點:查詢執行的各個階段中的准備查詢,每個唯一查詢一次。包括編寫查詢命令、基於模型和映射元數據生成命令樹和定義所返回數據的形狀的成本。因為實體 SQL查詢命令和 LINQ 查詢現已緩存，所以，以后執行相同查詢所需的時間較少。
如果有緩存的話,那么查詢命令轉成sql語句的性能會進一步提高,是不是ORM的效率更接近Ado.Net了呢?

性能注意點:此處參考了 http://www.cnblogs.com/jake1/archive/2013/04/25/3043664.html
a.在數據庫里面分頁
b.延遲加載要合理使用
c.需要連表的地方要連表查詢
d.查詢數據庫的次數和發出的sql語句的數量和長度
e.NoTracking的使用

表ContactInfo,GroupInfo說明:

CREATE TABLE [dbo].[ContactInfo](
    [ID] [int] IDENTITY(1,1) NOT NULL,
    [ContactId] [nvarchar](128) NOT NULL,
    [IsDelete] [int] NOT NULL,
    [Account] [nvarchar](64) NOT NULL,
    [ContactName] [nvarchar](50) NOT NULL,
    [CommonMobile] [nvarchar](50) NULL,
    [HeadPortrait] [nvarchar](256) NULL,
    [AttFile] [nvarchar](256) NULL,
    [GroupId] [int] NULL,
 CONSTRAINT [PK_ContactInfo] PRIMARY KEY CLUSTERED 
(
    [ID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

CREATE TABLE [dbo].[GroupInfo](
    [GroupId] [int] IDENTITY(1,1) NOT NULL,
    [GroupName] [nvarchar](300) NOT NULL,
 CONSTRAINT [PK_GroupInfo] PRIMARY KEY CLUSTERED 
(
    [GroupId] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

表的說明

1.0 分頁查詢

c#語句:

var db = new PhoneBookEntities();
db.GroupInfo.Where(c => c.GroupName.Length>=2).OrderByDescending(c => c.GroupId).Skip(2).Take(3).ToArray();

sql語句:

SELECT TOP (3) 
[Filter1].[GroupId] AS [GroupId], 
[Filter1].[GroupName] AS [GroupName]
FROM 
( SELECT [Extent1].[GroupId] AS [GroupId], [Extent1].[GroupName] AS [GroupName], 
row_number() OVER (ORDER BY [Extent1].[GroupId] DESC) AS [row_number]
FROM [dbo].[GroupInfo] AS [Extent1]
WHERE (LEN([Extent1].[GroupName])) >= 2
) AS [Filter1]

WHERE [Filter1].[row_number] > 2
ORDER BY [Filter1].[GroupId] DESC

2.0 FirstOrDefault,First

c#語句:

var db = new PhoneBookEntities();
db.GroupInfo.FirstOrDefault(c => c.GroupId == 1);

sql語句:

SELECT TOP (1) 
[Extent1].[GroupId] AS [GroupId], 
[Extent1].[GroupName] AS [GroupName]
FROM [dbo].[GroupInfo] AS [Extent1]
WHERE 1 = [Extent1].[GroupId]

延遲加載:

var db = new PhoneBookEntities();
var ci = db.ContactInfo.FirstOrDefault(c => c.ID == 9);

/* 此時產生的sql:*/

SELECT TOP (1) 
[Extent1].[ID] AS [ID], 
[Extent1].[ContactId] AS [ContactId], 
[Extent1].[IsDelete] AS [IsDelete], 
[Extent1].[Account] AS [Account], 
[Extent1].[ContactName] AS [ContactName], 
[Extent1].[CommonMobile] AS [CommonMobile], 
[Extent1].[HeadPortrait] AS [HeadPortrait], 
[Extent1].[AttFile] AS [AttFile], 
[Extent1].[GroupId] AS [GroupId]
FROM [dbo].[ContactInfo] AS [Extent1]
WHERE 9 = [Extent1].[ID]

var gn= ci.GroupInfo.GroupName;

/* (運行到此行c#代碼才會)產生sql:*/

exec sp_executesql N'SELECT 
[Extent1].[GroupId] AS [GroupId], 
[Extent1].[GroupName] AS [GroupName]
FROM [dbo].[GroupInfo] AS [Extent1]
WHERE [Extent1].[GroupId] = @EntityKeyValue1',N'@EntityKeyValue1 int',@EntityKeyValue1=1

如果是一條數據,用延遲加載是OK的.如果上面查詢有多條如10條結果,每條結果都使用到GroupInfo屬性,那么一共會有11條sql請求.效率低.應該使用連表,一條sql搞定.寫法如下.

第一種寫法 Join:

那如果是多條數據,應使用預加載.
c#語句:

var db = new PhoneBookEntities();
var ci = db.ContactInfo.Where(c => c.ID >3).Join(db.GroupInfo,c=>c.GroupId,g=>g.GroupId,(c,g)=>new{c.ContactName,g.GroupName});
foreach (var item in ci)
{
    MessageBox.Show(item.ContactName + "->" + item.GroupName);
}

sql語句:

SELECT 
[Extent1].[ID] AS [ID], 
[Extent1].[ContactName] AS [ContactName], 
[Extent2].[GroupName] AS [GroupName]
FROM [dbo].[ContactInfo] AS [Extent1]
INNER JOIN [dbo].[GroupInfo] AS [Extent2] ON [Extent1].[GroupId] = [Extent2].[GroupId]
WHERE [Extent1].[ID] > 3

說明:GroupJoin的用法,和Join使用類似.區別在於第四個參數resultSelector.

Join的第四個參數是 Func<ContactInfo,GroupInfo,anonymous type>.
GroupJoin的第四個參數是 Func<ContactInfo,IEnumerable<GroupInfo>,anonymous type>.
使用場景:聯系人和他的好友.聯系人一張表,好友關系一張表.聯系人表和好友關系表做連接,查出多個聯系人數據(包含他的好友),就應該使用GroupJoin.
簡單說:
public partial class ContactInfo
{
public int ID { get; set; }
public string ContactName { get; set; }
public Nullable<int> GroupId { get; set; }
public virtual GroupInfo GroupInfo { get; set; }
}
ContactInfo和GroupInfo一對一,該用Join;
如果是這種情況(僅僅是假設)
public partial class ContactInfo
{
public int ID { get; set; }
public string ContactName { get; set; }
public Nullable<int> GroupId { get; set; }
public virtual List<GroupInfo> GroupInfo { get; set; }
}
ContactInfo和GroupInfo一對多,該用GroupJoin;

第二種寫法 Include:

注意:數據庫設計ContactInfo,GroupInfo 要有主外鍵關系.
c#語句:

var db = new PhoneBookEntities();
var ci = db.ContactInfo.Include("GroupInfo").Where(c => c.ID > 3).Select(c => new { c.ContactName, c.GroupInfo.GroupName }); //或者 Include(c=>c.GroupInfo)
foreach (var item in ci)
{
    MessageBox.Show(item.ContactName + "->" + item.GroupName);
}

sql語句:

SELECT 
[Extent1].[ID] AS [ID], 
[Extent1].[ContactName] AS [ContactName], 
[Extent2].[GroupName] AS [GroupName]
FROM [dbo].[ContactInfo] AS [Extent1]
LEFT OUTER JOIN [dbo].[GroupInfo] AS [Extent2] ON [Extent1].[GroupId] = [Extent2].[GroupId]
WHERE [Extent1].[ID] > 3

3.0 Add

c#語句:

var db = new PhoneBookEntities();
var giModel = new GroupInfo();
giModel.GroupName = "Test";
db.GroupInfo.Add(giModel);
db.SaveChanges();
//Add方法之后,會把數據庫表記錄中的GroupId給giModel.

sql語句:

exec sp_executesql N'INSERT [dbo].[GroupInfo]([GroupName])
VALUES (@0)
SELECT [GroupId]
FROM [dbo].[GroupInfo]
WHERE @@ROWCOUNT > 0 AND [GroupId] = scope_identity()',N'@0 nvarchar(300)',@0=N'Test'

4.0 AddRange

c#語句:

var db = new PhoneBookEntities();
var gi = new GroupInfo[] { new GroupInfo() { GroupName = "g1" }, new GroupInfo() { GroupName = "g2" }, new GroupInfo() { GroupName = "g3" }, };
db.GroupInfo.AddRange(gi);
db.SaveChanges();

sql語句:

exec sp_executesql N'INSERT [dbo].[GroupInfo]([GroupName])
VALUES (@0)
SELECT [GroupId]
FROM [dbo].[GroupInfo]
WHERE @@ROWCOUNT > 0 AND [GroupId] = scope_identity()',N'@0 nvarchar(300)',@0=N'g1'

exec sp_executesql N'INSERT [dbo].[GroupInfo]([GroupName])
VALUES (@0)
SELECT [GroupId]
FROM [dbo].[GroupInfo]
WHERE @@ROWCOUNT > 0 AND [GroupId] = scope_identity()',N'@0 nvarchar(300)',@0=N'g2'

...

共執行3次.但是連接只打開關閉了1次.

5.0 Remove

c#語句:

var db = new PhoneBookEntities();
var ci= db.GroupInfo.FirstOrDefault(c => c.GroupId == 214);
db.GroupInfo.Remove(ci);
db.SaveChanges();

sql語句:

SELECT TOP (1) 
[Extent1].[GroupId] AS [GroupId], 
[Extent1].[GroupName] AS [GroupName]
FROM [dbo].[GroupInfo] AS [Extent1]
WHERE 214 = [Extent1].[GroupId]

exec sp_executesql N'DELETE [dbo].[GroupInfo]
WHERE ([GroupId] = @0)',N'@0 int',@0=214

感覺繁瑣啦?解決方案,1,自己定義方法;2,引用EntityFramework.Extended

來源https://www.nuget.org/packages/EntityFramework.Extended/或者在當前項目里,引用點擊右鍵,選擇管理NuGet程序包,聯機搜索並下載.
引用之后操作就簡單了.

c#語句:

var db = new PhoneBookEntities(); 
db.GroupInfo.Delete(c => c.GroupName == "Test");//過時的方法
db.GroupInfo.Where(c => c.GroupName == "Test").Delete();//如果查到的記錄數為0,也不報錯.上邊的先查 FirstOrDefault 后刪 Remove,你猜猜報錯嗎
db.SaveChanges();

sql語句:

DELETE [dbo].[GroupInfo]
FROM [dbo].[GroupInfo] AS j0 INNER JOIN (
SELECT 
[Extent1].[GroupId] AS [GroupId]
FROM [dbo].[GroupInfo] AS [Extent1]
WHERE N'Test' = [Extent1].[GroupName]
) AS j1 ON (j0.[GroupId] = j1.[GroupId])

一條sql語句搞定刪除.

6.0 更新操作

基於EntityFramework.Extended的更新操作.
c#語句:

db.GroupInfo.Where(c => c.GroupName.Contains("g")).Update(c => new GroupInfo() { GroupName = c.GroupName+"!"});
//此處沒有db.SaveChanges();,一樣執行了操作.

sql語句:

UPDATE [dbo].[GroupInfo] SET 
[GroupName] = [GroupName] + N'!' 
FROM [dbo].[GroupInfo] AS j0 INNER JOIN (
SELECT 
[Extent1].[GroupId] AS [GroupId]
FROM [dbo].[GroupInfo] AS [Extent1]
WHERE [Extent1].[GroupName] LIKE N'%g%'
) AS j1 ON (j0.[GroupId] = j1.[GroupId])

也是一條sql語句搞定批量修改.

(注意:update語句中只set了GroupName字段;
不用EntityFramework.Extended,用EF的先查后改,sql語句也是只set了GroupName字段.
更特殊的情況,以下例子:

var gi = db.GroupInfo.FirstOrDefault(c => c.GroupId == 219 );//此條記錄的GroupName為"Test"
gi.GroupName = "Test";
db.SaveChanges();

EF會自動優化,最終結果只有一個select語句,而沒有update語句. 此處細節,贊!

對比NHibernate 4,以下兩行代碼產生的sql語句會set Product表的[所有]字段
var pl = session.Query<Product>().FirstOrDefault(c => c.Name == "cnblogs");
pl.Name = "ICE";
)
如果先查出來要更改的數據,再修改.也是可以的. 但是從效率考慮,不管是c#寫法還是產生的sql語句,基於EntityFramework.Extended的更新操作更優.

7.0 EntityFramework.Extended中Future的使用

c#語句:

var db = new PhoneBookEntities();
var fci = db.ContactInfo.Where(c => c.ID > 1).FutureFirstOrDefault();
var fgi = db.GroupInfo.Where(c => c.GroupId > 2).FutureFirstOrDefault();
ContactInfo ci= fci.Value;
GroupInfo gi = fgi.Value;

//采用Future的寫法,不會立即查詢數據庫.只要調用結果的任意一個 .ToList,.ToArray或者.Value ,才會查數據庫.並且只發一個請求(Query #1 + Query #2 拼接好后發給數據庫,一起執行語句).

sql語句:

-- Query #1

SELECT TOP (1) 
[Extent1].[ID] AS [ID], 
[Extent1].[ContactId] AS [ContactId], 
[Extent1].[IsDelete] AS [IsDelete], 
[Extent1].[Account] AS [Account], 
[Extent1].[ContactName] AS [ContactName], 
[Extent1].[CommonMobile] AS [CommonMobile], 
[Extent1].[HeadPortrait] AS [HeadPortrait], 
[Extent1].[AttFile] AS [AttFile], 
[Extent1].[GroupId] AS [GroupId]
FROM [dbo].[ContactInfo] AS [Extent1]
WHERE [Extent1].[ID] > 1;

-- Query #2

SELECT TOP (1) 
[Extent1].[GroupId] AS [GroupId], 
[Extent1].[GroupName] AS [GroupName]
FROM [dbo].[GroupInfo] AS [Extent1]
WHERE [Extent1].[GroupId] > 2;

標注:EntityFramework.Extended相關部分參考了顧振印的博文: http://www.cnblogs.com/GuZhenYin/p/5482288.html

8.0 AsNoTracking

c#語句:

var db = new PhoneBookEntities();
var gi = db.GroupInfo.FirstOrDefault(c => c.GroupId == 219);
MessageBox.Show(db.Entry(gi).State.ToString());//Unchanged
var giAnk = db.GroupInfo.AsNoTracking().FirstOrDefault(c => c.GroupId == 219);
MessageBox.Show(db.Entry(giAnk).State.ToString());//Detached

免責聲明！

本站轉載的文章為個人學習借鑒使用，本站對版權不負任何法律責任。如果侵犯了您的隱私權益，請聯系本站郵箱yoyou2525@163.com刪除。