连接池应该比保持连接打开慢得多吗？

Question

正如我以前的问题：How to stay connected to database until screen close?

首先，让我向大家道歉，我不解释我的情况。

那么，我的情况是更新至多百条记录。我用For loop创建一个真正的工作并记录他们的结果。

private void button1_Click(object sender, EventArgs e) 
{ 
    int i; 
    KeyEventArgs keyEvent = new KeyEventArgs(Keys.Enter); //Create keydown event 

    Performance perf = new Performance(); //Class for measure time and logging 

    perf.Start(); //Start stopwatch 

    for (i = 1; i <= 100; i++) 
    { 
     txtLotNo.Text = i.ToString("0000000000") + "$01"; //Generate input ID 

     txtLotNo_KeyDown(sender, keyEvent); //Fire keydown event 
    } 

    perf.Stop(); //Stop stopwatch 

    perf.Log(frmInvCtrl.appPath,"Stock In (Stay connected)- " + frmInvCtrl.instance); //Logging 
} 

这是一个性能类。

class Performance 
{ 
    private Stopwatch _sw = new Stopwatch(); //Create stopwatch property 

    public double GetWatch 
    { 
     get 
     { 
      return this._sw.ElapsedMilliseconds; 
     } 
    } 

    public void Start() 
    { 
     Stop(); 

     _sw.Reset(); 
     _sw.Start(); 
    } 

    public void Stop() 
    { 
     if (_sw.IsRunning) 
     { 
      _sw.Stop(); 
     } 
    } 

    public void Log(string path,string menu) 
    { 
     string logName = path + "\\Log_" + System.DateTime.Now.ToString("yyyyMMdd") + ".txt"; 
     string logDetail = System.DateTime.Now.ToString("yyyy/MM/dd hh:mm:ss") + " - [" + menu + "] " 
      + "Process 100 record in [" + (((double)_sw.ElapsedMilliseconds/1000)).ToString() + "] seconds"; 

     using(StreamWriter writer = new StreamWriter(logName,true)) 
     { 
      writer.WriteLine(logDetail); //wirtelog 
     } 
    } 
} 

而这些日志结果

2017/02/19 08:16:05 - [Stock In - On Cloud] Process 100 record in [68.352] seconds 
2017/02/19 08:17:34 - [Stock In - On Cloud] Process 100 record in [70.184] seconds 
2017/02/19 08:20:28 - [Stock In - On Cloud] Process 100 record in [56.66] seconds 
2017/02/19 08:21:34 - [Stock In - On Cloud] Process 100 record in [60.605] seconds 
2017/02/19 08:22:44 - [Stock In - On Cloud] Process 100 record in [68.27] seconds 
2017/02/19 08:24:43 - [Stock In - Network Server] Process 100 record in [46.86] seconds 
2017/02/19 08:26:05 - [Stock In - Network Server] Process 100 record in [31.746] seconds 
2017/02/19 08:26:48 - [Stock In - Network Server] Process 100 record in [31.859] seconds 
2017/02/19 08:27:32 - [Stock In - Network Server] Process 100 record in [31.003] seconds 
2017/02/19 08:28:17 - [Stock In - Network Server] Process 100 record in [40.487] seconds 
2017/02/19 08:32:42 - [Stock In (Stay connected)- On Cloud] Process 100 record in [18.196] seconds 
2017/02/19 08:35:47 - [Stock In (Stay connected)- On Cloud] Process 100 record in [14.721] seconds 
2017/02/19 08:36:30 - [Stock In (Stay connected)- On Cloud] Process 100 record in [15.903] seconds 
2017/02/19 08:37:31 - [Stock In (Stay connected)- On Cloud] Process 100 record in [15.811] seconds 
2017/02/19 08:38:15 - [Stock In (Stay connected)- On Cloud] Process 100 record in [16.4] seconds 
2017/02/19 08:43:08 - [Stock In (Stay connected)- Network Server] Process 100 record in [13.09] seconds 
2017/02/19 08:43:25 - [Stock In (Stay connected)- Network Server] Process 100 record in [13.03] seconds 
2017/02/19 08:43:40 - [Stock In (Stay connected)- Network Server] Process 100 record in [13.051] seconds 
2017/02/19 08:43:55 - [Stock In (Stay connected)- Network Server] Process 100 record in [12.992] seconds 
2017/02/19 08:44:12 - [Stock In (Stay connected)- Network Server] Process 100 record in [14.953] seconds 

我是用连接池实施。但是，在许多记录情况下，显示的连接数据库的这些结果更快。

有没有适合这种情况的习惯？

编辑：2017年2月21日

下面是当打开表单代码开放的连接：

private void frm_Load(object sender, EventArgs e) //Open menu 
{ 
    ... //statement 

    frmMain.sqlConn1 = new SqlConnection(); 
    frmMain.sqlConn1.ConnectionString = frmMain.connectionString1; 
    frmMain.sqlConn1.Open(); 

    ... //statement 
} 

更新代码：

public static long ScanUpdate(string lotNo) 
{ 
    string scanLotNo = ""; 
    int scanIndex = 0; 

    if (!SplitBarcode(lotNo, ref scanLotNo, ref scanIndex)) 
    { 
     //Invalid Barcode data 
     return -919; 
    } 

    //Prepare sql command 
    string updStatus = (frmMain.shelfScan) ? "05" : "10"; 
    string sql = <sql statement> 

    try 
    { 
     using (SqlCommand sqlCmd = new SqlCommand(sql, frmMain.sqlConn1)) //frmMain.sqlConn1 is connection in form_Load() 
     { 
      if (sqlCmd.ExecuteNonQuery() <= 0) 
      { 
       //No row affect 
       //frmMain.sndPlay.Play(); 
       return -99; 
      } 
      else 
      { 
       //Completed 
       return 0; 
      } 
     } 
    } 
    catch 
    { 
     return 99; 
    } 
    finally 
    { 

    } 
} 

和Dispose连接时退出

private void btnBack_Click(object sender, EventArgs e) 
{ 
    frmMain.sqlConn1.Dispose(); 
    this.Close(); 
} 

Answer 1

大家在这里失踪的部分是它的Windows CE，它在紧凑版上的并不罕见的开放连接可能非常慢。

不过，这些时间看起来有点夸张。有关解决方法，请参阅此QA： How can I make my SQL Server CE connection open faster?

Answer 2

从单线程响应性的角度来看，保持连接打开将会更快。连接池的目的是通过在线程之间共享连接池来降低打开新连接的开销，同时不会消耗共享SQL Server上的过多连接数。

每次连接释放到连接池并重新使用时，协议栈都会调用sp_resetconnection来清除服务器上的状态。您可以通过针对SQL Server运行分析器跟踪来查看此信息。

由于每个进程对于每个连接字符串都有自己的连接池，因此如果在进程内存在连接争用，您将只能从连接池中受益。

Answer 3

有几个领域，您可以遇到上述代码的问题。

• 您正在创建单个SqlConnection实例。
• 所有的事件处理程序调用引用一个SqlConnection实例的静态函数。
• 您的事件处理程序不检查它们是否在主UI线程上运行。

该SqlConnection类将自动池连接下的封面。当您拨打close()函数时，连接只会回到池中。您可以使用连接字符串中的属性控制池化行为。通过为所有函数保留相同的连接对象，你迫使它们被序列化。

这是reference to some connection string properties。看看Connection Lifetime。

我会从form_load()功能删除SqlConnection实例，写ScanUpdate如下：

public static long ScanUpdate(string lotNo) 
{ 
    string scanLotNo = ""; 
    int scanIndex = 0; 

    if (!SplitBarcode(lotNo, ref scanLotNo, ref scanIndex)) 
    { 
     //Invalid Barcode data 
     return -919; 
    } 

    //Prepare sql command 
    string updStatus = (frmMain.shelfScan) ? "05" : "10"; 
    string sql = <sql statement> 

    try 
    { 
     using (SqlConnection conn = new SqlConection(frmMain.connectionString1)) { 
      SqlCommand sqlCmd = new SqlCommand(sql, conn); 
      if (sqlCmd.ExecuteNonQuery() <= 0) 
      { 
       //No row affect 
       //frmMain.sndPlay.Play(); 
       return -99; 
      } 
      else 
      { 
       //Completed 
       return 0; 
      } 
      conn.Close(); 
     }    
    } 
    catch 
    { 
     return 99; 
    } 
} 

为了您*_Click事件处理函数，请务必检查，以检查事件需要被重新调用：

private void button1_Click(object sender, EventArgs e) 
{ 
    if (this.InvokeRequired) 
    { 
     this.Invoke(new EventArgsDelegate(button1_Click), new object[] { sender, ea }); 
    } 

    // Do some stuff 
} 

有关事件处理的更详细见this answer。