sql server死锁：identify导致的 insert 和 select max(id)

【1】死锁信息

【1.1】图

　　

左边：select max(id) from tab 
右边：insert into tab values.....

两个语句是同一个表，id是主键、聚集索引

【1.2】XML

Deadlock graph    <deadlock-list>
 <deadlock victim="process9ada68">
  <process-list>
   <process id="process9ada68" taskpriority="0" logused="0" waitresource="PAGE: 102:1:5940067" waittime="3953" ownerId="1571798125" transactionname="user_transaction" lasttranstarted="2020-11-16T12:04:38.950" XDES="0x55282258" lockMode="S" schedulerid="2" kpid="2896" status="suspended" spid="80" sbid="1" ecid="0" priority="0" transcount="1" lastbatchstarted="2020-11-16T12:04:38.950" lastbatchcompleted="2020-11-16T12:04:38.950" clientapp="Microsoft SQL Server" hostname="iZqcugpmvybrkfZ" hostpid="1596" loginname="sa" isolationlevel="read committed (2)" xactid="1571798125" currentdb="102" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
    <executionStack>
     <frame procname="adhoc" line="1" sqlhandle="0x020000002b707300c7eefdadd6f8dfe7f8457b5eb4e02c32">
SELECT MAX(&quot;Tbl1002&quot;.&quot;ID&quot;) &quot;Expr1003&quot; FROM &quot;QPRecordDB&quot;.&quot;dbo&quot;.&quot;RecordUserInout&quot; &quot;Tbl1002&quot;     </frame>
     <frame procname="unknown" line="1" sqlhandle="0x000000000000000000000000000000000000000000000000">
unknown     </frame>
    </executionStack>
    <inputbuf>
Proc [Database Id = 32767 Object Id = 315066412]    </inputbuf>
   </process>
   <process id="processfe03e8" taskpriority="0" logused="620" waitresource="PAGE: 102:1:5940068" waittime="3953" ownerId="1571798118" transactionname="user_transaction" lasttranstarted="2020-11-16T12:04:38.950" XDES="0x37f294a8" lockMode="IX" schedulerid="3" kpid="4960" status="suspended" spid="83" sbid="1" ecid="0" priority="0" transcount="2" lastbatchstarted="2020-11-16T12:04:38.950" lastbatchcompleted="2020-11-16T12:04:38.950" clientapp="Microsoft SQL Server" hostname="iZqcugpmvybrkfZ" hostpid="1596" loginname="sa" isolationlevel="read committed (2)" xactid="1571798118" currentdb="102" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
    <executionStack>
     <frame procname="adhoc" line="1" stmtstart="316" sqlhandle="0x020000002109bb37cd7e5870d56e6418e1fe6003a303a1c9">
INSERT [QPRecordDB].[dbo].[RecordUserInout]([UserID],[KindID],[ServerID],[EnterScore],[EnterUserMedal],[EnterLoveliness],[EnterMachine],[EnterClientIP]) VALUES(@Param000004,@Param000005,@Param000006,@Param000007,@Param000008,@Param000009,@Param000010,@Param000011)     </frame>
     <frame procname="unknown" line="1" sqlhandle="0x000000000000000000000000000000000000000000000000">
unknown     </frame>
    </executionStack>
    <inputbuf>
(@Param000004 int,@Param000005 int,@Param000006 int,@Param000007 bigint,@Param000008 int,@Param000009 int,@Param000010 nvarchar(33),@Param000011 nvarchar(15))INSERT [QPRecordDB].[dbo].[RecordUserInout]([UserID],[KindID],[ServerID],[EnterScore],[EnterUserMedal],[EnterLoveliness],[EnterMachine],[EnterClientIP]) VALUES(@Param000004,@Param000005,@Param000006,@Param000007,@Param000008,@Param000009,@Param000010,@Param000011)    </inputbuf>
   </process>
  </process-list>
  <resource-list>
   <pagelock fileid="1" pageid="5940067" dbid="102" objectname="QPRecordDB.dbo.RecordUserInout" id="lockffffffff80008e00" mode="IX" associatedObjectId="72057594056540160">
    <owner-list>
     <owner id="processfe03e8" mode="IX"/>
    </owner-list>
    <waiter-list>
     <waiter id="process9ada68" mode="S" requestType="wait"/>
    </waiter-list>
   </pagelock>
   <pagelock fileid="1" pageid="5940068" dbid="102" objectname="QPRecordDB.dbo.RecordUserInout" id="lockffffffffb86aa940" mode="S" associatedObjectId="72057594056540160">
    <owner-list>
     <owner id="process9ada68" mode="S"/>
    </owner-list>
    <waiter-list>
     <waiter id="processfe03e8" mode="IX" requestType="wait"/>
    </waiter-list>
   </pagelock>
  </resource-list>
 </deadlock>
</deadlock-list>
    

【2】分析思路

【2.1】语句分析

select max(id) from RecordUserInout

（1） 当我用max(id)查询的时候，它会顺着索引去找最大的，比如找到了最大记录在这个页，它会这个页上加上S锁

（2） 接着insert into values插入的时候，它需要同时在这两个页上写数据，于是向这个页上加IX锁

（3） 但是第一个页已经加了S锁，于是第一个页的IX就会等待，但是第二个页就不需要

怎么想都感觉不是很对

难道是这样？

（1）select max(id) 要扫描整个聚集索引树才能找到max(id)，对聚集索引树页都加了S锁
（2）同时，在select max(id) 还没找到的时候，insert into 插入到了最后面，然后它排它X了， 然后它需要X锁来更新聚集索引上层页
（3）但这个时候上层页正在被select 给S锁阻塞住了
（4）select max(id) 的后续扫描又被 insert 的X锁给阻塞了

感觉其实也不是很对，既然

【2.2】思路分析

可能是跟踪只是捕获到当前语句，但没有语句所在事务的相关上下文，找程序看一看

【3】解决思路

对select max(id)  from tab 做  with(nolock)