SQL Server 2008：U 和 X 锁 - 在没有任何索引的一张表上死锁。如何？

Question

我观察到我的数据库非常奇怪的行为。 我有一张小表（大约 300 行），其中一个字段不断更新。

我在那里遇到了很多死锁 - 表的更新导致同一张表的类似更新死锁（U 锁与 X 锁）。

所以我决定删除聚集索引（所以表现在没有任何索引）来修复死锁。但它没有帮助，现在我在 U 和 X 锁定模式之间陷入僵局。

所以一张表，没有索引和 2 个会话更新一张表

受害者

update dbo.MyNumber set
  @nextno = nextno = nextno + 1
where [type] = @type
  and yearid = @yearid

获胜查询：

update dbo.MyNumber set
  @nextno = nextno = nextno + 1
where [type] = @TYPE
  and yrclosedyn = 0

行肯定不同，但页面相同。

这怎么可能？也许它与锁升级有关，或者......？

我非常感谢任何建议。

提前致谢 迈克

死锁 XML：

<deadlock-list>
 <deadlock victim="process6c492e8">
  <process-list>
   <process id="processb6a988" taskpriority="0" logused="1848" waitresource="RID: 5:1:127478:16" waittime="3478" ownerId="17153439" transactionname="user_transaction" lasttranstarted="2012-12-18T12:31:40.147" XDES="0xffffffff89482258" lockMode="U" schedulerid="7" kpid="4248" status="suspended" spid="98" sbid="0" ecid="0" priority="0" transcount="2" lastbatchstarted="2012-12-18T12:31:49.913" lastbatchcompleted="2012-12-18T12:31:49.913" clientapp="PenAIR" hostname="S16047425" hostpid="9300" loginname="sa" isolationlevel="read committed (2)" xactid="17153439" currentdb="5" lockTimeout="4294967295" clientoption1="673185824" clientoption2="128056">
    <executionStack>
     <frame procname="MYDATABASE.dbo.MyStoredProcedure" line="92" stmtstart="9062" stmtend="9388" sqlhandle="0x030005002d15a05e58b5710016a100000100000000000000">
UPDATE dbo.MyNumber Set
  @NEXTNO = NEXTNO = NEXTNO + 1
WHERE  (TYPE = @TYPE) AND (YRCLOSEDYN = 0)     </frame>
    </executionStack>
    <inputbuf>
Proc [Database Id = 5 Object Id = 1587549485]    </inputbuf>
   </process>
   <process id="process6c492e8" taskpriority="0" logused="192" waitresource="RID: 5:1:127478:20" waittime="8252" ownerId="17153562" transactionname="user_transaction" lasttranstarted="2012-12-18T12:31:45.140" XDES="0x6583b1e0" lockMode="U" schedulerid="13" kpid="19824" status="suspended" spid="143" sbid="0" ecid="0" priority="0" transcount="2" lastbatchstarted="2012-12-18T12:31:45.140" lastbatchcompleted="2012-12-18T12:31:45.140" clientapp="PenAIR" hostname="S16047425" hostpid="4760" loginname="sa" isolationlevel="read committed (2)" xactid="17153562" currentdb="5" lockTimeout="4294967295" clientoption1="673185824" clientoption2="128056">
    <executionStack>
     <frame procname="MYDATABASE.dbo.MyStoredProcedure" line="92" stmtstart="9062" stmtend="9388" sqlhandle="0x030005002d15a05e58b5710016a100000100000000000000">
UPDATE dbo.MyNumber Set
  @NEXTNO = NEXTNO = NEXTNO + 1
WHERE  ([TYPE] = @TYPE) AND (YRCLOSEDYN = 0)     </frame>
    </executionStack>
    <inputbuf>
Proc [Database Id = 5 Object Id = 1587549485]    </inputbuf>
   </process>
  </process-list>
  <resource-list>
   <ridlock fileid="1" pageid="127478" dbid="5" objectname="MYDATABASE.dbo.MyNumber" id="lock464f2640" mode="X" associatedObjectId="72057594131120128">
    <owner-list>
     <owner id="processb6a988" mode="X"/>
    </owner-list>
    <waiter-list>
     <waiter id="process6c492e8" mode="U" requestType="wait"/>
    </waiter-list>
   </ridlock>
   <ridlock fileid="1" pageid="127478" dbid="5" objectname="MYDATABASE.dbo.MyNumber" id="lockfffffffff1974980" mode="X" associatedObjectId="72057594131120128">
    <owner-list>
     <owner id="process6c492e8" mode="X"/>
    </owner-list>
    <waiter-list>
     <waiter id="processb6a988" mode="U" requestType="wait"/>
    </waiter-list>
   </ridlock>
  </resource-list>
 </deadlock>
</deadlock-list>

Answer 1

Shredding your deadlock graph转换成表格形式显示如下。

+----------+-------------------------+-----------+-----------+------------+----------+--------------------+--------------------+---------+
| LockMode |      LockedObject       | TranCount | LockEvent | LockedMode | WaitMode |    WaitResource    |   IsolationLevel   | LogUsed |
+----------+-------------------------+-----------+-----------+------------+----------+--------------------+--------------------+---------+
| U        | MYDATABASE.dbo.MyNumber | NULL      | rid       | X          | U        | RID: 5:1:127478:20 | read committed (2) |     192 |
| U        | MYDATABASE.dbo.MyNumber | NULL      | rid       | X          | U        | RID: 5:1:127478:16 | read committed (2) |    1848 |
+----------+-------------------------+-----------+-----------+------------+----------+--------------------+--------------------+---------+

你还没有回答我在 cmets 中关于序列生成代码是否在每个事务中只调用一次的问题。

如果没有，很容易生成类似于您帖子中的死锁图。

设置

CREATE TABLE dbo.MyNumber
  (
     [TYPE]     CHAR(1),
     YRCLOSEDYN INT,
     NEXTNO     INT
  )

INSERT INTO dbo.MyNumber
VALUES      ('X', 0, 1),
            ('Y', 0, 1)

GO

CREATE PROC MyStoredProcedure @TYPE   CHAR(1),
                              @NEXTNO INT OUTPUT
AS
    UPDATE dbo.MyNumber
    SET    @NEXTNO = NEXTNO = NEXTNO + 1
    WHERE  ( [TYPE] = @TYPE )
           AND ( YRCLOSEDYN = 0 )

连接 1

BEGIN TRAN

DECLARE @NEXTNO INT

EXEC MyStoredProcedure 'Y', @NEXTNO OUTPUT

WAITFOR DELAY '00:00:05'

EXEC MyStoredProcedure 'X', @NEXTNO OUTPUT

ROLLBACK 

连接 2

（执行连接1中的代码后立即运行）

BEGIN TRAN
DECLARE @NEXTNO INT

EXEC MyStoredProcedure 'X', @NEXTNO OUTPUT

EXEC MyStoredProcedure 'Y', @NEXTNO OUTPUT

ROLLBACK

其中的死锁图输出与上面的非常相似

+----------+-------------------------+-----------+-----------+------------+----------+-----------------+--------------------+---------+
| LockMode |      LockedObject       | TranCount | LockEvent | LockedMode | WaitMode |  WaitResource   |   IsolationLevel   | LogUsed |
+----------+-------------------------+-----------+-----------+------------+----------+-----------------+--------------------+---------+
| U        | MYDATABASE.dbo.MyNumber |         2 | rid       | X          | U        | RID: 11:1:144:1 | read committed (2) |     248 |
| U        | MYDATABASE.dbo.MyNumber |         2 | rid       | X          | U        | RID: 11:1:144:0 | read committed (2) |     248 |
+----------+-------------------------+-----------+-----------+------------+----------+-----------------+--------------------+---------+

如果这是对您问题的解释，您需要确保在所有事务中以相同的顺序更新序列（我认为您不能只使用 an IDENTITY column based solution 一定有充分的理由）