Question

我偶尔会在sql server中遇到死锁。我创建了一个锁定非数据库操作（信用卡处理）的功能，因此不会发生重复操作。我的功能如下（抱歉tcl，但sql足够清晰）。任何人都可以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]"

}

Answer 1

尝试将UPDLOCK添加到第一个选择以强制独占锁定
尝试为此类操作提供的sp_getapplock。

我更喜欢2号，个人......

Answer 2

拥有死锁图会很有用。

SQL死锁的发生不仅仅是因为涉及查询，而且涉及的模式同样重要。例如，您可以获得具有完全有效和“正确”查询的Reader-Writer deadlocks，因为读取和写入选择不同的数据访问路径。如果在GranularLocks上存在timeActionMade的索引并且不包含'object'列，我可以看到这种情况发生在你的情况下。但同样，解决方案将取决于实际的死锁是什么。

在sqlserver中获取死锁

2 个答案: