c# - 插入，选择，删除的SQL Server死锁

Question

申请详情

C# web api(隐式并发)

用于执行 sql 的 dapper

要求

当四个用户被添加到“休息室”时，这意味着游戏已准备好开始。第四个添加的用户负责启动游戏。游戏开始后，必须将用户从“休息室”中移除。

表格

UserInLounge (LoungeId, UserId)注意，比lounge还多一个，

代码

var tran = connection.BeginTransaction();
connection.Execute("insert into UserInLounge(LoungeId, UserId, TimeEntered) values (@loungeId, @userId, @timeEntered)", new { loungeId, userId = user.Id, timeEntered = DateTime.UtcNow }, tran);
var userIds = connection.Query<string>("select UserId from UserInLounge where LoungeId = @loungeId", new { loungeId }, tran).ToList();
if (userIds.Count == 4)
{
    connection.Execute("delete from UserInLounge where LoungeId = @loungeId and UserId IN @userIds", new { loungeId, userIds }, tran);
}
tran.Commit();

问题

多用户运行(我用4个测试)会造成事务死锁。我使用一个事务，因为我需要在插入后准确知道现在是否有四个人，如果是，则将他们删除。

第二次尝试

var tran = connection.BeginTransaction();
var userIds = connection.Query<string>("select UserId from UserInLounge where LoungeId = @loungeId", new { loungeId }, tran).ToList();
if (userIds.Count == 3)
{
    connection.Execute("delete from UserInLounge where LoungeId = @loungeId and UserId IN @userIds", new { loungeId, userIds }, tran);
    tran.Commit();
}
else
{
    connection.Execute("insert into UserInLounge(LoungeId, UserId, TimeEntered) values (@loungeId, @userId, @timeEntered)", new { loungeId, userId = user.Id, timeEntered = DateTime.UtcNow }, tran);
tran.Commit();
 Log.InfoFormat("{0} added to Lounge: {1}; Now {2} users", user.UserName, ret.Name, userIds.Count);

}

第二次尝试时，if 语句永远不会为真。这是日志输出-

|INFO |FiveHundred.Web.Stores.DapperLoungeStore - user3@fivehundred.com added to Lounge: Main; Now 0 users
|INFO |FiveHundred.Web.Stores.DapperLoungeStore - user2@fivehundred.com added to Lounge: Main; Now 0 users
|INFO |FiveHundred.Web.Stores.DapperLoungeStore - user1@fivehundred.com added to Lounge: Main; Now 0 users
|INFO |FiveHundred.Web.Stores.DapperLoungeStore - user4@fivehundred.com added to Lounge: Main; Now 0 users

如果我按照建议添加 HOLDLOCK，我会遇到死锁

"select UserId from UserInLounge with (holdlock) where LoungeId = @loungeId"

Answer 1

我从这里得到了解决方案 - http://michaeljswart.com/2011/09/mythbusting-concurrent-updateinsert-solutions/

与上面基本相同，但加上 -

var tran = connection.BeginTransaction(IsolationLevel.Serializable);
var userIds = connection.Query<string>("select UserId from UserInLounge with (updlock) where LoungeId = @loungeId", new { loungeId }, tran).ToList();