SQL CLR-lock语句有什么区别吗？

Question

I have written the following piece of code ( sql clr stored procedure ) that writes messages to a local file. The problem occurs when multiple connections call the stored proc at the same time. So I used a lock statement. But this doesn't seem to make any difference? What am I doing wrong here?

lock (SqlContext.Pipe)
{
    StreamWriter sw = File.AppendText("C:\Date.txt");
    int y = 50;

    while (y != 0)
    {
        sw.WriteLine(DateTime.Now + " " + serverName + " -- " + jobId.ToString() );
        System.Threading.Thread.Sleep(new Random().Next());
        y = y - 1;
    }
    sw.Close();

}

Answer 1

lock statement on its own doesn't protect anything. The magic happens only when all threads lock the same object . In you case, each thread locks its own context pipe, the behavior is going to be identical with or without lock.

Besides, from all the damage a CLR procedure can do inside SQL, hijacking a SQL worker to wait in Sleep() is definitely a top offender. I hope you only use it for experimental purposes.

To achieve what you probably want, ie. have only one procedure execute at any time, use an application lock: sp_getapplock . Either wrap the CLR procedure call in T-SQL sp_getapplock / sp_releaseapplock , or execute sp_getapplock on the context connection from your CLR code (and execute sp_releaseapplock on your way out).