在sql server中获取死锁

Posted 2023-03-23

【中文标题】在sql server中获取死锁

【英文标题】：Getting deadlocks in sqlserver

【发布时间】：2009-10-26 20:59:25

【问题描述】：

我偶尔会在 sql server 中遇到死锁。我创建了一个用于锁定非数据库操作（信用卡处理）的函数，因此不会发生重复。我的函数如下（对不起tcl，但是sql已经够清楚了）。谁能看到为什么偶尔会发生死锁？？？？

proc ims_syn_lock_object  db object timeout 30 wait 1     
    if [catch 
        while true 
            am_dbtransaction begin $db

            # read the object locks that aren't timed out       
            set result [am_db1cell $db "SELECT object from GranularLocks WITH (ROWLOCK,HOLDLOCK) where object = [ns_dbquotevalue $object] AND  timeActionMade > DATEADD(second,-timeout, GETDATE())"]

            # check to see if this object is locked and not timed out
            if  [string equal "" $result]  
                break;
             else 
                # another process has this object and it is not timed out. 
                # release the row lock
                am_dbtransaction rollback $db

                if  $wait  
                    # sleep for between 400 and 800 miliseconds
                    sleep [expr [ns_rand 400] + 400]                    
                 else 
                    # we aren't waiting on locked resources.
                    return 0;
                
                        
        

        # either the object lock has timed out, or the object isn't locked
        # create the object lock.          
        ns_db dml $db "DELETE FROM GranularLocks  WHERE object = [ns_dbquotevalue $object]"
        ns_db dml $db "INSERT INTO GranularLocks(object,timeout) VALUES ([ns_dbquotevalue $object],[ns_dbquotevalue $timeout int])"   

        # releases the row lock and commits the transaction
        am_dbtransaction commit $db    

     errMsg] 
        ns_log Notice "Could not lock $object. $errMsg"
        catch  
            am_dbtransaction rollback $db 
         errMsg
        return 0
    
    return 1     




proc ims_syn_unlock_object db object  

    #simply remove the objects lock
    ns_db dml $db "DELETE FROM GranularLocks WHERE object = [ns_dbquotevalue $object]"

【参考方案1】：

尝试将 UPDLOCK 添加到第一个选择以强制排他锁

试试为这种操作提供的sp_getapplock。

我个人更喜欢 2 号...

【讨论】：

我发誓我已经把那个holdlock读成updlock了，哈哈。我很确定你成功了。

【参考方案2】：

有死锁图会很有用。

SQL 死锁的发生不仅是因为涉及的查询，而且同样重要的是涉及的架构。例如，您可以获得具有完全有效和“正确”查询的Reader-Writer deadlocks，这仅仅是因为读取和写入选择了不同的数据访问路径。如果在不覆盖“对象”列的 GranularLocks 上存在 timeActionMade 索引，我可以看到这种情况发生。但同样，解决方案将取决于实际的死锁是什么。