Question

我在一个相对简单的查询中遇到了僵局：

select coalesce((select max(id) from table where year < 2016),0)

错误：事务在使用另一个进程的通用可等待对象资源上死锁，并被选为死锁牺牲品。重新运行该交易。

详细说明：

该表大小约为40GB，行数为283M
该表具有聚簇列存储索引。
id是一个bigint和一个身份。
该表按年分区。
MaxDOP设置为4，成本阈值设置为50。
8个逻辑核心和32GB RAM，存储是非搜索SSD。
计算机正在运行Windows 8.1和SQL Server 2016 SP1 Developer 版。

如果我使用isnull而不是coalesce，则不会发生错误。

死锁图：

 <?xml version="1.0" encoding="UTF-8"?>
<deadlock>
   <victim-list>
      <victimProcess id="process697ca6c108" />
   </victim-list>
   <process-list>
      <process id="process697ca6c108" taskpriority="0" logused="20000" waittime="2630" schedulerid="4" kpid="648" status="suspended" spid="62" sbid="0" ecid="3" priority="0" trancount="0" lastbatchstarted="2017-04-10T09:30:00.030" lastbatchcompleted="2017-04-10T09:30:00.030" lastattention="1900-01-01T00:00:00.030" clientapp="Microsoft SQL Server Management Studio - Query" hostname="MyHost" hostpid="6328" isolationlevel="read committed (2)" xactid="90846084" currentdb="9" lockTimeout="4294967295" clientoption1="671090784" clientoption2="390200">
         <executionStack>
            <frame procname="adhoc" line="1" stmtend="160" sqlhandle="0x0200000000342d3438c95d7d95220ffb20aa484d79bf55d20000000000000000000000000000000000000000">unknown</frame>
         </executionStack>
         <inputbuf>select coalesce( (select max(id) from MyTable where year &amp;lt; 2016),0)</inputbuf>
      </process>
      <process id="process697c9c1088" taskpriority="0" logused="20000" waittime="3923" schedulerid="6" kpid="9016" status="suspended" spid="62" sbid="0" ecid="2" priority="0" trancount="0" lastbatchstarted="2017-04-10T09:30:00.030" lastbatchcompleted="2017-04-10T09:30:00.030" lastattention="1900-01-01T00:00:00.030" clientapp="Microsoft SQL Server Management Studio - Query" hostname="MyHost" hostpid="6328" isolationlevel="read committed (2)" xactid="90846084" currentdb="9" lockTimeout="4294967295" clientoption1="671090784" clientoption2="390200">
         <executionStack>
            <frame procname="adhoc" line="1" stmtend="160" sqlhandle="0x0200000000342d3438c95d7d95220ffb20aa484d79bf55d20000000000000000000000000000000000000000">unknown</frame>
         </executionStack>
         <inputbuf>select coalesce( (select max(id) from MyTable where year &amp;lt; 2016),0)</inputbuf>
      </process>
      <process id="process697ca4f848" taskpriority="0" logused="20000" waittime="3923" schedulerid="5" kpid="11792" status="suspended" spid="62" sbid="0" ecid="4" priority="0" trancount="0" lastbatchstarted="2017-04-10T09:30:00.030" lastbatchcompleted="2017-04-10T09:30:00.030" lastattention="1900-01-01T00:00:00.030" clientapp="Microsoft SQL Server Management Studio - Query" hostname="MyHost" hostpid="6328" isolationlevel="read committed (2)" xactid="90846084" currentdb="9" lockTimeout="4294967295" clientoption1="671090784" clientoption2="390200">
         <executionStack>
            <frame procname="adhoc" line="1" stmtend="160" sqlhandle="0x0200000000342d3438c95d7d95220ffb20aa484d79bf55d20000000000000000000000000000000000000000">unknown</frame>
         </executionStack>
         <inputbuf>select coalesce( (select max(id) from MyTable where year &amp;lt; 2016),0)</inputbuf>
      </process>
      <process id="process697ca38ca8" taskpriority="0" logused="20000" waittime="3923" schedulerid="2" kpid="16468" status="suspended" spid="62" sbid="0" ecid="1" priority="0" trancount="0" lastbatchstarted="2017-04-10T09:30:00.030" lastbatchcompleted="2017-04-10T09:30:00.030" lastattention="1900-01-01T00:00:00.030" clientapp="Microsoft SQL Server Management Studio - Query" hostname="MyHost" hostpid="6328" isolationlevel="read committed (2)" xactid="90846084" currentdb="9" lockTimeout="4294967295" clientoption1="671090784" clientoption2="390200">
         <executionStack>
            <frame procname="adhoc" line="1" stmtend="160" sqlhandle="0x0200000000342d3438c95d7d95220ffb20aa484d79bf55d20000000000000000000000000000000000000000">unknown</frame>
         </executionStack>
         <inputbuf>select coalesce( (select max(id) from MyTable where year &amp;lt; 2016),0)</inputbuf>
      </process>
   </process-list>
   <resource-list>
      <SyncPoint>
         <owner-list>
            <owner id="process697c9c1088" />
            <owner id="process697ca38ca8" />
            <owner id="process697ca4f848" />
         </owner-list>
         <waiter-list>
            <waiter id="process697ca6c108" />
         </waiter-list>
      </SyncPoint>
      <SyncPoint>
         <owner-list>
            <owner id="process697ca6c108" />
         </owner-list>
         <waiter-list>
            <waiter id="process697c9c1088" />
         </waiter-list>
      </SyncPoint>
      <SyncPoint>
         <owner-list>
            <owner id="process697ca6c108" />
         </owner-list>
         <waiter-list>
            <waiter id="process697ca4f848" />
         </waiter-list>
      </SyncPoint>
      <SyncPoint>
         <owner-list>
            <owner id="process697ca6c108" />
         </owner-list>
         <waiter-list>
            <waiter id="process697ca38ca8" />
         </waiter-list>
      </SyncPoint>
   </resource-list>
</deadlock>

Generic Waitable Object上的死锁 - Coalesce v IsNull？

0 个答案: