如何摆脱SQL Server 2005和C#应用程序中的死锁？

Question

我在C#for Windows服务中有一个代码,它主要负责更新我的数据库中的表中的记录,但是我的日志中总是出现很多错误,所有错误都是关于资源的死锁,

这是错误:

System.Data.SqlClient.SqlException(0x80131904):事务(进程ID 57)在锁资源上与另一个进程死锁,并被选为死锁牺牲品.重新运行该交易.在System.Data.SqlClient.SqlConnection.OnError(SqlException异常,Boolean breakConnection,Action1 wrapCloseInAction) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose) at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady) at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString) at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async, Int32 timeout, Task& task, Boolean asyncWrite) at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, TaskCompletionSourceSystem.Data.SqlClient.SqlCommand.ExecuteNonQuery的System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1完成,String methodName,Boolean sendToPipe,Int32 timeout,Boolean asyncWrite)中的1完成,Int32超时,任务和任务,布尔asyncWrite) ()在WheelTrackListener.DataAccess.SQLDBA.ExecuteNQuery(SqlCommand cmd,Boolean isShowError,ConnectionStringType CountryCode,String deviceID,Int32 retry,String functionCallName)ClientConnectionId:e45e4cf1-a113-46b7-b9b5-dc5ee8111406

现在,我想问一下,我可以尝试或检查资源是否被锁定？如果锁定如何等待更新,直到它被释放？

这是我目前的代码:

public static int updateVehicleLastPosition(string UTCDate, string UTC_Time, 
              string NS_Indicator, string Latitude, string EWIndicator, 
              string Longtitude, string Speed, string Processed, 
              string Near_ByLocation, string Near_ByLocation_AR, 
              string Gis_dataID, string address, string ar_adress, string Device_ID)
{
        SQLMethods sql = new SQLMethods();
        SqlCommand cmd = sql.cmdUpdateVehicleLastPosition(UTCDate, UTC_Time, NS_Indicator, Latitude, EWIndicator, Longtitude, Speed, Processed, Near_ByLocation, Near_ByLocation_AR, Gis_dataID, address, ar_adress, Device_ID);
        SQLDBA sqlDBA = new SQLDBA();
        return sqlDBA.ExecuteNQuery(cmd, true, ConnectionStringType.OMN, Device_ID, 10, "updateVehicleLastPosition");
}

public SqlCommand cmdUpdateVehicleLastPosition(string UTCDate, string UTC_Time, 
                      string NS_Indicator, string Latitude, string EWIndicator, 
                      string Longtitude, string Speed, string Processed, 
                      string Near_ByLocation, string Near_ByLocation_AR, 
                      string Gis_dataID, string address, string ar_adress, 
                      string Device_ID)
 {
        string sql = "UPDATE CTS_VehicleLastPosition SET [UTCDate] = @UTCDate, [UTC_Time] = @UTC_Time, [NS_Indicator] = @NS_Indicator, [Latitude] = @Latitude, [EWIndicator] = @EWIndicator, [Longtitude] = @Longtitude, [Speed] = @Speed, [Processed] = @Processed, [Near_ByLocation] = @Near_ByLocation, [Near_ByLocation_AR] = @Near_ByLocation_AR, [Gis_dataID] = @Gis_dataID, [address] = @address, [ar_adress] = @ar_adress WHERE [Device_ID] = @Device_ID";

        SqlCommand cmd = new SqlCommand(sql);
        cmd.Parameters.AddWithValue("@UTCDate", UTCDate);
        cmd.Parameters.AddWithValue("@UTC_Time", UTC_Time);
        cmd.Parameters.AddWithValue("@NS_Indicator", NS_Indicator);
        cmd.Parameters.AddWithValue("@Latitude", Latitude);
        cmd.Parameters.AddWithValue("@EWIndicator", EWIndicator);
        cmd.Parameters.AddWithValue("@Longtitude", Longtitude);
        cmd.Parameters.AddWithValue("@Speed", Speed);
        cmd.Parameters.AddWithValue("@Processed", Processed);
        cmd.Parameters.AddWithValue("@Near_ByLocation", Near_ByLocation);
        cmd.Parameters.AddWithValue("@Near_ByLocation_AR", Near_ByLocation_AR);
        cmd.Parameters.AddWithValue("@Gis_dataID", Gis_dataID);
        cmd.Parameters.AddWithValue("@address", address);
        cmd.Parameters.AddWithValue("@ar_adress", ar_adress);
        cmd.Parameters.AddWithValue("@Device_ID", Device_ID);
        return cmd;
}

public int ExecuteNQuery(SqlCommand cmd, bool isShowError, 
                    DataAccess.ConnectionStringType CountryCode, string deviceID, 
                    int retry, string functionCallName)
{
        ConnectionManager Connection = new ConnectionManager();
        try
        {
            Connection.GetConnection(CountryCode);
            if ((Connection.con == null) || (Connection.con.State != ConnectionState.Open))
            {
                if (retry <= 0) return 0;
                else return ExecuteNQuery(cmd, isShowError, CountryCode, deviceID, retry - 1, functionCallName);
            }
            int rowsAffected = 0;
            cmd.Connection = Connection.con;
            rowsAffected = cmd.ExecuteNonQuery();
            return rowsAffected;
        }
        catch (SqlException sqlexception)
        {
            if (isShowError)
                LEAMRALogger.Logger.WriteByDate("Logs\\SQLDBA\\" + functionCallName + "\\" + String.Format("{0:dd-MM-yyyy}", DateTime.Now), "SQLDBA", "SQLDBA_ERROR", "ExecuteNQuery Function: [deviceID: " + deviceID + " | retry: " + retry + "] " + sqlexception.ToString());
        }
        catch (Exception ex)
        {
            if (isShowError)
                LEAMRALogger.Logger.WriteByDate("Logs\\SQLDBA\\" + functionCallName + "\\" + String.Format("{0:dd-MM-yyyy}", DateTime.Now), "SQLDBA", "SQLDBA_ERROR", "ExecuteNQuery Function: [deviceID: " + deviceID + " | retry: " + retry + "] " + ex.ToString());
        }
        finally
        {
            if ((Connection.con != null) && (Connection.con.State == ConnectionState.Open))
            {
                Connection.con.Close();
                Connection.con.Dispose();
            }

            GC.Collect();
        }
        if (retry <= 0) return 0;
        else return ExecuteNQuery(cmd, isShowError, CountryCode, deviceID, retry - 1, functionCallName);
}

Answer 1

我在代码中看不到任何明确的事务范围,因此我不知道在您进行更新时已经存在哪些锁; 还不清楚你正在使用什么隔离级别.但是在这种情况下最常见的情况是,在同一事务中,您在稍后尝试升级的相同行上发出了select(读锁定).这将导致锁升级,如果两个事务尝试执行相同的操作,则可能导致死锁:

1. 事务A:选择读锁定
2. 事务B:选择读锁定
3. 事务A:更新 - 想要将其读锁升级为写锁,但必须等待事务B释放其读锁
4. 事务B:更新 - 想要将其读锁升级为写锁,但必须等待事务A释放其读锁.

答对了!死锁,因为A和B都在等待彼此释放现有的读锁,然后才能进行更新.

要防止这种情况,您需要在选择中使用updlock提示,例如,

select * from table with (updlock) where blah blah

这将确保您的select使用写锁定而不是读锁定,这将防止并发事务之间的锁升级.