提示

Question

我有一个僵局，我不知道如何解决。我已经修复了来自EF端的其他一些查询，这些查询导致了相同的死锁（在sp的同一行），但是无法修改，这是一个非常基本的查询，我认为必须有一种更简便的方法来重写SP或修改索引以避免页面锁定。

三个表：

工作项（Id，DMC等）
收费（Id，...）
ChargeItems（Id，Charge_Id，Workitem_Id，...）

两个过程：

被多次调用的EF查询。（〜5-10 /分钟）
一种存储过程，它通过将存档移至另一个数据库并从源中删除它们来存档数据。

僵局：

当SP尝试删除空的Charges时，它在最后一步被抛出，其中ChargeItems没有记录。至此，它已经删除了所有ChargeItems，只需要删除空的Charge和工作项。

当SP尝试删除费用时，EF所运行的查询正在通过其DMC搜索工作项。

SELECT 
    [Limit1].[Id] AS [Id], 
    [Limit1].[DMC] AS [DMC], 
    [Limit1].[FirstSeen] AS [FirstSeen], 
    [Limit1].[DrawingNo] AS [DrawingNo], 
    [Limit1].[MachineId] AS [MachineId], 
    [Limit1].[WorkItemState_Id] AS [WorkItemState_Id], 
    [Limit1].[ItemType_Id] AS [ItemType_Id], 
    [Limit1].[Repaired] AS [Repaired], 
    [Limit1].[MachineCycle] AS [MachineCycle], 
    [Limit1].[FirstSeenCheck] AS [FirstSeenCheck], 
    [Limit1].[LastSeen] AS [LastSeen], 
    [Limit1].[Archive] AS [Archive], 
    [Limit1].[CastingDateString] AS [CastingDateString], 
    [Limit1].[Deleted] AS [Deleted], 
    [Limit1].[DMC2] AS [DMC2], 
    [Limit1].[Id1] AS [Id1], 
    [Limit1].[WorkPlace_Id] AS [WorkPlace_Id], 
    [Limit1].[CastingFormIdent_Id] AS [CastingFormIdent_Id], 
    [Limit1].[FormIdentItemType_Id] AS [FormIdentItemType_Id]
    FROM ( SELECT TOP (1) 
        [Extent1].[Id] AS [Id], 
        [Extent1].[DMC] AS [DMC], 
        [Extent1].[FirstSeen] AS [FirstSeen], 
        [Extent1].[DrawingNo] AS [DrawingNo], 
        [Extent1].[MachineId] AS [MachineId], 
        [Extent1].[WorkItemState_Id] AS [WorkItemState_Id], 
        [Extent1].[ItemType_Id] AS [ItemType_Id], 
        [Extent1].[Repaired] AS [Repaired], 
        [Extent1].[MachineCycle] AS [MachineCycle], 
        [Extent1].[FirstSeenCheck] AS [FirstSeenCheck], 
        [Extent1].[LastSeen] AS [LastSeen], 
        [Extent1].[Archive] AS [Archive], 
        [Extent1].[CastingDateString] AS [CastingDateString], 
        [Extent1].[Deleted] AS [Deleted], 
        [Extent1].[DMC2] AS [DMC2], 
        [Extent1].[WorkPlace_Id] AS [WorkPlace_Id], 
        [Extent1].[CastingFormIdent_Id] AS [CastingFormIdent_Id], 
        [Extent1].[FormIdentItemType_Id] AS [FormIdentItemType_Id], 
        [Extent2].[Id] AS [Id1]
        FROM WorkItems AS [Extent1]
        LEFT OUTER JOIN [dbo].[ChargeItems] AS [Extent2] ON [Extent1].[Id] = [Extent2].[WorkItem_Id]
        WHERE ([Extent1].[DMC] = '') OR (([Extent1].[DMC] IS NULL))
    )  AS [Limit1]

所选的执行计划：

部分SP：

;with chargesToDelete(id, ciid) as (
                    select c.id, ci.Id from @chargeids c
                    left join dbo.chargeitems ci on ci.Charge_Id = c.id
                    where ci.id is null
                )

                delete from dbo.charges
                    where Id in (select id from chargesToDelete)

死图XML：

    <deadlock>
 <victim-list>
  <victimProcess id="process6472ad498" />
 </victim-list>
 <process-list>
  <process id="process6472ad498" taskpriority="5" logused="152924" waitresource="PAGE: 5:1:531207 " waittime="794" ownerId="10001638" transactionname="DELETE" lasttranstarted="2018-08-29T11:50:14.510" XDES="0x6ff07f078" lockMode="IX" schedulerid="7" kpid="7620" status="suspended" spid="89" sbid="0" ecid="0" priority="-5" trancount="2" lastbatchstarted="2018-08-29T11:22:53.457" lastbatchcompleted="2018-08-29T11:22:53.457" lastattention="1900-01-01T00:00:00.457" clientapp="Microsoft SQL Server Management Studio - Query" hostname="PCSERVER151" hostpid="6480" loginname="PRC\administrator" isolationlevel="read uncommitted (1)" xactid="10001638" currentdb="5" lockTimeout="4294967295" clientoption1="673187936" clientoption2="390200">
   <executionStack>
    <frame procname="LP_R.dbo.Archive_Finish" line="190" stmtstart="12876" stmtend="13044" sqlhandle="0x03000500063ecd76e962c80014a9000001000000000000000000000000000000000000000000000000000000">
delete from LP_R.dbo.workitems where id in (select id from @workitemIds);    </frame>
    <frame procname="LP_R.dbo.Archive" line="64" stmtstart="5142" stmtend="5244" sqlhandle="0x030005007886b57874f2b30014a9000001000000000000000000000000000000000000000000000000000000">
exec Archive_Finish @Day, @Dryrun, @MaxWorkitems;    </frame>
    <frame procname="adhoc" line="4" stmtstart="62" stmtend="200" sqlhandle="0x0100050010f3f82c309a63770600000000000000000000000000000000000000000000000000000000000000">
EXEC    @return_value = [dbo].[Archive]
        @Day = 450,
        @Dryrun = 0    </frame>
   </executionStack>
   <inputbuf>

DECLARE @return_value int

EXEC    @return_value = [dbo].[Archive]
        @Day = 450,
        @Dryrun = 0

SELECT  'Return Value' = @return_value

   </inputbuf>
  </process>
  <process id="process66f184558" taskpriority="0" logused="0" waitresource="PAGE: 5:1:114492 " waittime="913" ownerId="10002051" transactionname="SELECT" lasttranstarted="2018-08-29T11:50:15.210" XDES="0x6b379ad00" lockMode="S" schedulerid="5" kpid="3860" status="suspended" spid="67" sbid="2" ecid="0" priority="0" trancount="0" lastbatchstarted="2018-08-29T11:50:15.210" lastbatchcompleted="2018-08-29T11:50:15.210" lastattention="1900-01-01T00:00:00.210" clientapp="EntityFramework" hostname="PCSERVER151" hostpid="3520" loginname="sa" isolationlevel="read committed (2)" xactid="10002051" currentdb="5" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
   <executionStack>
    <frame procname="adhoc" line="1" stmtstart="56" sqlhandle="0x02000000412fd7099fe0d3410b538a2193192ac8c5143cf20000000000000000000000000000000000000000">
SELECT 
    [Limit1].[Id] AS [Id], 
    [Limit1].[DMC] AS [DMC], 
    [Limit1].[FirstSeen] AS [FirstSeen], 
    [Limit1].[DrawingNo] AS [DrawingNo], 
    [Limit1].[MachineId] AS [MachineId], 
    [Limit1].[WorkItemState_Id] AS [WorkItemState_Id], 
    [Limit1].[ItemType_Id] AS [ItemType_Id], 
    [Limit1].[Repaired] AS [Repaired], 
    [Limit1].[MachineCycle] AS [MachineCycle], 
    [Limit1].[FirstSeenCheck] AS [FirstSeenCheck], 
    [Limit1].[LastSeen] AS [LastSeen], 
    [Limit1].[Archive] AS [Archive], 
    [Limit1].[CastingDateString] AS [CastingDateString], 
    [Limit1].[Deleted] AS [Deleted], 
    [Limit1].[DMC2] AS [DMC2], 
    [Limit1].[Id1] AS [Id1], 
    [Limit1].[WorkPlace_Id] AS [WorkPlace_Id], 
    [Limit1].[CastingFormIdent_Id] AS [CastingFormIdent_Id], 
    [Limit1].[FormIdentItemType_Id] AS [FormIdentItemType_Id]
    FROM ( SELECT TOP (1) 
        [Extent1].[Id] AS [Id], 
        [Extent1].[DMC] AS [DMC], 
        [Extent1].[FirstSeen] AS [FirstSeen], 
        [Extent1    </frame>
    <frame procname="unknown" line="1" sqlhandle="0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000">
unknown    </frame>
   </executionStack>
   <inputbuf>
(@p__linq__0 nvarchar(4000))SELECT 
    [Limit1].[Id] AS [Id], 
    [Limit1].[DMC] AS [DMC], 
    [Limit1].[FirstSeen] AS [FirstSeen], 
    [Limit1].[DrawingNo] AS [DrawingNo], 
    [Limit1].[MachineId] AS [MachineId], 
    [Limit1].[WorkItemState_Id] AS [WorkItemState_Id], 
    [Limit1].[ItemType_Id] AS [ItemType_Id], 
    [Limit1].[Repaired] AS [Repaired], 
    [Limit1].[MachineCycle] AS [MachineCycle], 
    [Limit1].[FirstSeenCheck] AS [FirstSeenCheck], 
    [Limit1].[LastSeen] AS [LastSeen], 
    [Limit1].[Archive] AS [Archive], 
    [Limit1].[CastingDateString] AS [CastingDateString], 
    [Limit1].[Deleted] AS [Deleted], 
    [Limit1].[DMC2] AS [DMC2], 
    [Limit1].[Id1] AS [Id1], 
    [Limit1].[WorkPlace_Id] AS [WorkPlace_Id], 
    [Limit1].[CastingFormIdent_Id] AS [CastingFormIdent_Id], 
    [Limit1].[FormIdentItemType_Id] AS [FormIdentItemType_Id]
    FROM ( SELECT TOP (1) 
        [Extent1].[Id] AS [Id], 
        [Extent1].[DMC] AS [DMC], 
        [Extent1].[FirstSeen] AS [F   </inputbuf>
  </process>
 </process-list>
 <resource-list>
  <pagelock fileid="1" pageid="531207" dbid="5" subresource="FULL" objectname="LP_R.dbo.WorkItems" id="lock6d7b2d800" mode="S" associatedObjectId="72057594043891712">
   <owner-list>
    <owner id="process66f184558" mode="S" />
   </owner-list>
   <waiter-list>
    <waiter id="process6472ad498" mode="IX" requestType="wait" />
   </waiter-list>
  </pagelock>
  <pagelock fileid="1" pageid="114492" dbid="5" subresource="FULL" objectname="LP_R.dbo.WorkItems" id="lock5cd1a2b00" mode="IX" associatedObjectId="72057594043891712">
   <owner-list>
    <owner id="process6472ad498" mode="IX" />
   </owner-list>
   <waiter-list>
    <waiter id="process66f184558" mode="S" requestType="wait" />
   </waiter-list>
  </pagelock>
 </resource-list>
</deadlock>

Answer 1

（作为旁注）

delete c 
from dbo.charges c
inner join @chargeids t
  on t.id = c.id
where not exists(
  select 1 from dbo.chargeitems ci 
  where ci.Charge_id = c.id
)

我想在这个阶段实际上还没有chargeitems。并且可能在此delete语句之前将它们删除了。因此，归档流程事务可能要比显示的更长。

因此，您的删除过程将删除特定的rows并在页面上放置一个Intent-X锁，而读取过程则可能以不同的顺序扫描pages。 FK s可以放置更多的锁（如果有）。

提示

看看select语句的实际执行计划。它没有顺序地请求TOP 1，使用远远不够精确的where谓词，并在chargeitems上加入workitem_id（也许上面没有索引）。修复它可能有助于在阅读时摆脱scan（如果有）。也许您可以尝试选择top1 workitem，然后再选择top1 chargeitem。

例如，您可以尝试在读取语句上应用READPAST提示（不会等待锁定的页面）或将删除语句的粒度提高到PAGLOCK。如果删除过程很少执行，并且对本系统来说还不错，请尝试TABLOCK进行删除。

UPD

实际上，我错过了要点：您指的是从charges中删除，而死锁位于WorkItem上（如死锁图清楚地显示）。但这并不能抵消其余的假设。如执行计划所示，WorkItem是真正扫描的，而删除是在特定行上执行的：

delete from LP_R.dbo.workitems where id in (select id from @workitemIds);

您可以应用我帖子中的提示来选择语句和/或删除语句（所有这些都在归档过程中）。

Answer 2

首先，由于此死锁中有S锁，请考虑将数据库切换为READ COMMITTED SNAPSHOT，以便您的SELECT查询将使用行版本控制而不是S锁来读取数据库。一键解决所有S / X死锁和其他阻塞，但是您需要进行测试。

第二，要解决此僵局，请在存储过程中使用事务，并尽早获得大锁。例如，代替IX锁，它强制使用TABLOCKX提示获取排他表锁。仅当两个会话 first 获得兼容的锁，然后以后尝试获取不兼容的锁时，才会发生死锁。 IX和S锁是此死锁的开始，因此您可以通过确保存储过程不获取弱IX来阻止它，并等待直到它可以获取将使其成功完成的锁为止。 >

IX页锁的SQL Server死锁

2 个答案:

提示

UPD