确定死锁的原因

Question

我有2+并发进程。在它们内部有一个执行重复验证(select) +保存(insert)操作的迭代。以下是关于死锁的sql-server-profiler信息：

<deadlock-list>
     <deadlock victim="process8e09048">
      <process-list>
       <process id="process8e09048" taskpriority="0" logused="1088" waitresource="PAGE: 29:1:376823" waittime="920" ownerId="1276429306" transactionname="user_transaction" lasttranstarted="2012-09-26T20:59:44.367" XDES="0x3077833c0" lockMode="S" schedulerid="1" kpid="4872" status="suspended" spid="79" sbid="0" ecid="0" priority="0" trancount="1" lastbatchstarted="2012-09-26T20:59:44.427" lastbatchcompleted="2012-09-26T20:59:44.427" clientapp=".Net SqlClient Data Provider" hostname="PORTAL" hostpid="5348" loginname="IIS APPPOOL\ASP.NET v4.0 Classic" isolationlevel="read committed (2)" xactid="1276429306" currentdb="29" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
        <executionStack>
         <frame procname="adhoc" line="1" stmtstart="282" sqlhandle="0x02000000b79df8046665e3984d6dc129fec20a3029fce9bc">
    SELECT id FROM [WP_CashCenter_StockTransactionLine] WHERE StockTransaction_id=@StockTransaction_id and Direction=@Direction and IsVerified=@IsVerified and QualificationType=@QualificationType and id &lt;&gt; @id and Product_id is null and Material_id=@Material_id and StockContainer_id is null and StockLocation_id=@StockLocation_id     </frame>
         <frame procname="unknown" line="1" sqlhandle="0x000000000000000000000000000000000000000000000000">
    unknown     </frame>
        </executionStack>
        <inputbuf>
    (@id bigint,@StockTransaction_id bigint,@Direction int,@IsVerified bit,@QualificationType int,@Material_id nvarchar(3),@StockLocation_id int)SELECT id FROM [WP_CashCenter_StockTransactionLine] WHERE StockTransaction_id=@StockTransaction_id and Direction=@Direction and IsVerified=@IsVerified and QualificationType=@QualificationType and id &lt;&gt; @id and Product_id is null and Material_id=@Material_id and StockContainer_id is null and StockLocation_id=@StockLocation_id    </inputbuf>
       </process>
       <process id="process5c13948" taskpriority="0" logused="2636" waitresource="PAGE: 29:1:376823" waittime="920" ownerId="1276429252" transactionname="user_transaction" lasttranstarted="2012-09-26T20:59:44.337" XDES="0x222e64e80" lockMode="S" schedulerid="6" kpid="2956" status="suspended" spid="70" sbid="0" ecid="0" priority="0" trancount="1" lastbatchstarted="2012-09-26T20:59:44.427" lastbatchcompleted="2012-09-26T20:59:44.427" clientapp=".Net SqlClient Data Provider" hostname="PORTAL" hostpid="5348" loginname="IIS APPPOOL\ASP.NET v4.0 Classic" isolationlevel="read committed (2)" xactid="1276429252" currentdb="29" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
        <executionStack>
         <frame procname="adhoc" line="1" stmtstart="238" sqlhandle="0x02000000d77dd1038a9b7f6d7158436117c042e42767242d">
    SELECT id FROM [WP_CashCenter_StockTransactionLine] WHERE StockTransaction_id=@StockTransaction_id and Direction=@Direction and IsVerified=@IsVerified and QualificationType=@QualificationType and id &lt;&gt; @id and Product_id is null and Material_id=@Material_id and StockContainer_id is null and StockLocation_id is null     </frame>
         <frame procname="unknown" line="1" sqlhandle="0x000000000000000000000000000000000000000000000000">
    unknown     </frame>
        </executionStack>
        <inputbuf>
    (@id bigint,@StockTransaction_id bigint,@Direction int,@IsVerified bit,@QualificationType int,@Material_id nvarchar(3))SELECT id FROM [WP_CashCenter_StockTransactionLine] WHERE StockTransaction_id=@StockTransaction_id and Direction=@Direction and IsVerified=@IsVerified and QualificationType=@QualificationType and id &lt;&gt; @id and Product_id is null and Material_id=@Material_id and StockContainer_id is null and StockLocation_id is null    </inputbuf>
       </process>
      </process-list>
      <resource-list>
       <pagelock fileid="1" pageid="376823" dbid="29" objectname="Edsson_WebPortal_v5.01.dbo.WP_CashCenter_StockTransactionLine" id="lock9302c80" mode="IX" associatedObjectId="72057594148028416">
        <owner-list>
         <owner id="process5c13948" mode="IX"/>
        </owner-list>
        <waiter-list>
         <waiter id="process8e09048" mode="S" requestType="convert"/>
        </waiter-list>
       </pagelock>
       <pagelock fileid="1" pageid="376823" dbid="29" objectname="Edsson_WebPortal_v5.01.dbo.WP_CashCenter_StockTransactionLine" id="lock9302c80" mode="IX" associatedObjectId="72057594148028416">
        <owner-list>
         <owner id="process8e09048" mode="IX"/>
        </owner-list>
        <waiter-list>
         <waiter id="process5c13948" mode="S" requestType="convert"/>
        </waiter-list>
       </pagelock>
      </resource-list>
     </deadlock>
    </deadlock-list>

​

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语句是selects conditions。这些selects的where子句仅使用包含在非聚集索引中的列。执行计划：

​

Answer 1

在这个死锁图中，两个进程都成功地执行了插入，并且在同一页上持有IX锁。它们必须在同一页中的两个单独行上也持有一个X锁。

由于SELECT被NC索引覆盖，因此死锁所涉及的页面必须属于NC索引。

您的SELECT语句正在尝试获取一个页级锁，该锁已经通过INSERT语句拥有一个IX锁。

因此，如果您的插入不属于同一StockTransaction_id，只需将行锁提示添加到SELECT就可以解决死锁情况。

RCSI保证读取器不会被写入器阻塞，反之亦然。但是，如果您的应用程序设计依赖于任何阻塞行为，这可能是一个问题。

您可以阅读更多关于由于不同的锁粒度here而导致的死锁的信息