Question

今天我们有一个非常有趣的案例让我很烦恼。简而言之，我们进行了一些重构，从重复的代码中清除触发器，将其提取到单个可重用的存储过程中。我们认为这种重构没有副作用，但我们错了。发布后，我们遇到了很多死锁和性能下降，没有明显的原因。在检查系统表以查看所采用的DB之后，我们发现上面的重构已经涉及，我们最终还是回滚了更新。

我们没有在测试环境中重现问题来探测治疗方法，因此需要一些棘手的条件才能使问题可见。

以下是变更内容的详细信息。我们更新了很多触发器，但它们都非常相似，我会告诉你一个。它应该足够了，因为我发现死锁图表显示存在死锁，其中两个进程正在执行单个触发器（显示如下）并且死锁。

让我先从之前有效的解决方案开始（我们回滚到这个解决方案，看起来几乎与下面所示的死锁解决方案完全相同）。

CREATE TRIGGER [dbo].[TR__xyz__update_sync_publishers]
ON [dbo].[xyz]
AFTER INSERT, DELETE, UPDATE
AS 
BEGIN
    SET NOCOUNT ON;

    if(TRIGGER_NESTLEVEL() = 1)
    BEGIN
        create table #AffectedIDs (advisor_id int primary key)

        insert into #AffectedIDs
            select distinct t.id
            from
                (select id 
                 from inserted
                 inner join xyz a ON a.id = id
                 where [text] <> ''
                 union 
                 select id 
                 from inserted
                 inner join xyz a ON a.id = id
                 where [text] <> '') t

        declare @date datetime = getutcdate()
        declare @RegisteredObjectTypeID int = 2
        declare @SyncPublisherSourceID int = 1

        update pub
        set pub.master_update_date = @date
        from #AffectedIDs affected
        inner join sync_publishers pub on 
            pub.sync_registered_object_type_id = @RegisteredObjectTypeID 
            and pub.sync_publisher_source_id = @SyncPublisherSourceID
            and pub.sync_object_id = affected.advisor_id

        insert into sync_publishers (sync_object_id, sync_registered_object_type_id, sync_publisher_source_id , master_update_date)
        select 
            affected.advisor_id,
            @RegisteredObjectTypeID,
            @SyncPublisherSourceID,
            @date
        from #AffectedIDs affected
        left join sync_publishers pub on 
            pub.sync_registered_object_type_id = @RegisteredObjectTypeID
            and pub.sync_publisher_source_id = @SyncPublisherSourceID
            and pub.sync_object_id = affected.advisor_id
        where 
            pub.sync_object_id is null

        drop table #AffectedIDs
    END
END

这是死锁的新触发器。

CREATE TRIGGER [dbo].[TR__xyz__update_sync_publishers]
   ON [dbo].[xyz]
   AFTER INSERT,DELETE,UPDATE
AS 
BEGIN

    SET NOCOUNT ON;

    declare @ids dtInt

    insert into @ids
    select distinct t.id
    from
    (
        select id from inserted
        INNER JOIN xyz a ON a.id = id
        WHERE [text] <> ''
        union 
        select id from inserted
        INNER JOIN xyz a ON a.id = id
        WHERE [text] <> ''
    ) t

    exec SyncTracker_PublishEvent 2, @ids

END

以下是提取SP的定义：

CREATE PROCEDURE [dbo].[SyncTracker_PublishEvent]
    @objectTypeId int, 
    @ids dtInt readonly
AS
BEGIN
    SET NOCOUNT ON;

    if(TRIGGER_NESTLEVEL() > 1) RETURN;

    declare @pubSourceId int = 1
    declare @date datetime = getutcdate()

    update pub
    set pub.master_update_date = @date
    from @ids affected
    inner join sync_publishers pub
    on pub.sync_registered_object_type_id = @objectTypeId 
        and pub.sync_publisher_source_id = @pubSourceId
        and pub.sync_object_id = affected.value

    insert into sync_publishers (sync_object_id, sync_registered_object_type_id, sync_publisher_source_id , master_update_date)
    select affected.value, @objectTypeId, @pubSourceId, @date
    from @ids affected
    left join sync_publishers pub
    on pub.sync_registered_object_type_id = @objectTypeId
        and pub.sync_publisher_source_id = @pubSourceId
        and pub.sync_object_id = affected.value
    where 
        pub.sync_object_id is null
END
GO

dtInt的定义。

CREATE TYPE [dbo].[dtInt] AS TABLE
(
    [value] [int] NOT NULL,
    PRIMARY KEY CLUSTERED 
    (
        [value] ASC
    )
)

最后是死锁图。

<deadlock>
  <victim-list>
    <victimProcess id="processe1892fe8c8" />
  </victim-list>
  <process-list>
    <process id="processe1892fe8c8" taskpriority="0" logused="3824" waitresource="KEY: 5:72057602924150784 (4776e78e2961)" waittime="5686" ownerId="2583257965" transactionname="user_transaction" lasttranstarted="2016-10-03T08:30:42.500" XDES="0xe192b24408" lockMode="U" schedulerid="6" kpid="41296" status="suspended" spid="141" sbid="0" ecid="0" priority="0" trancount="2" lastbatchstarted="2016-10-03T08:30:42.503" lastbatchcompleted="2016-10-03T08:30:42.493" lastattention="2016-10-03T08:29:01.693" clientapp="..." hostname="..." hostpid="22572" loginname="kbuser" isolationlevel="read committed (2)" xactid="2583257965" currentdb="5" lockTimeout="4294967295" clientoption1="673316896" clientoption2="128056">
      <executionStack>
        <frame procname="63c1b4d8-1c55-4429-b057-81fb6da8f780.dbo.SyncTracker_PublishEvent" line="21" stmtstart="1178" stmtend="1680" sqlhandle="0x030005007bf23c4b5012b40092a6000001000000000000000000000000000000000000000000000000000000">
update pub
    set pub.master_update_date = @date
    from @ids affected
    inner join sync_publishers pub
    on pub.sync_registered_object_type_id = @objectTypeId 
        and pub.sync_publisher_source_id = @pubSourceId
        and pub.sync_object_id = affected.valu    </frame>
        <frame procname="63c1b4d8-1c55-4429-b057-81fb6da8f780.dbo.TR__xyz__update_sync_publishers" line="28" stmtstart="1300" stmtend="1372" sqlhandle="0x03000500f711233ddee4c60090a6000000000000000000000000000000000000000000000000000000000000">
exec SyncTracker_PublishEvent 2, @id    </frame>
        <frame procname="unknown" line="1" stmtstart="1054" stmtend="3032" sqlhandle="0x02000000912653235c5ef3529289f19ae4445e62ee1ccbc00000000000000000000000000000000000000000">
unknown    </frame>
        <frame procname="unknown" line="1" sqlhandle="0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000">
unknown    </frame>
      </executionStack>
    </process>
    <process id="processdfa401b848" taskpriority="0" logused="9384" waitresource="KEY: 5:72057602924150784 (1501093f83b4)" waittime="5814" ownerId="2582414029" transactionname="user_transaction" lasttranstarted="2016-10-03T08:30:09.933" XDES="0x104486ac408" lockMode="U" schedulerid="1" kpid="19548" status="suspended" spid="213" sbid="0" ecid="0" priority="0" trancount="2" lastbatchstarted="2016-10-03T08:30:53.047" lastbatchcompleted="2016-10-03T08:30:53.047" lastattention="1900-01-01T00:00:00.047" clientapp="..." hostname="..." hostpid="6196" loginname="kbuser" isolationlevel="read committed (2)" xactid="2582414029" currentdb="5" lockTimeout="4294967295" clientoption1="673316896" clientoption2="128056">
      <executionStack>
        <frame procname="63c1b4d8-1c55-4429-b057-81fb6da8f780.dbo.SyncTracker_PublishEvent" line="21" stmtstart="1178" stmtend="1680" sqlhandle="0x030005007bf23c4b5012b40092a6000001000000000000000000000000000000000000000000000000000000">
update pub
    set pub.master_update_date = @date
    from @ids affected
    inner join sync_publishers pub
    on pub.sync_registered_object_type_id = @objectTypeId 
        and pub.sync_publisher_source_id = @pubSourceId
        and pub.sync_object_id = affected.valu    </frame>
        <frame procname="63c1b4d8-1c55-4429-b057-81fb6da8f780.dbo.TR__xyz__update_sync_publishers" line="28" stmtstart="1300" stmtend="1372" sqlhandle="0x03000500f711233ddee4c60090a6000000000000000000000000000000000000000000000000000000000000">
exec SyncTracker_PublishEvent 2, @id    </frame>
        <frame procname="unknown" line="1" stmtstart="1120" stmtend="3132" sqlhandle="0x020000007414d821ed68a2ab4462b4eca6b2fdb4ba28cc350000000000000000000000000000000000000000">
unknown    </frame>
        <frame procname="unknown" line="1" sqlhandle="0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000">
unknown    </frame>
      </executionStack>
    </process>
  </process-list>
  <resource-list>
    <keylock hobtid="72057602924150784" dbid="5" objectname="63c1b4d8-1c55-4429-b057-81fb6da8f780.dbo.sync_publishers" indexname="IX__sync_publishers__registered_object_type_id__sync_object_id" id="lock10887a96b00" mode="X" associatedObjectId="72057602924150784">
      <owner-list>
        <owner id="processdfa401b848" mode="X" />
      </owner-list>
      <waiter-list>
        <waiter id="processe1892fe8c8" mode="U" requestType="wait" />
      </waiter-list>
    </keylock>
    <keylock hobtid="72057602924150784" dbid="5" objectname="63c1b4d8-1c55-4429-b057-81fb6da8f780.dbo.sync_publishers" indexname="IX__sync_publishers__registered_object_type_id__sync_object_id" id="lockdb7d7b8200" mode="X" associatedObjectId="72057602924150784">
      <owner-list>
        <owner id="processe1892fe8c8" mode="X" />
      </owner-list>
      <waiter-list>
        <waiter id="processdfa401b848" mode="U" requestType="wait" />
      </waiter-list>
    </keylock>
  </resource-list>
</deadlock>

此处提供了sync_publishers的定义：http://pastebin.com/LviwwCDi。

如果您对可行原因有任何想法 - 欢迎分享 - 我们将非常感谢！

更新1. UPDATE / INSERT到sync_publishers的实际执行计划

实际执行计划看起来非常相似。

新的执行计划（偶尔死锁）。

老执行计划（没有）。

更新2.尝试了一些建议

我今天尝试了一些建议：

由于删除列中的非聚集索引中缺少sync_publisher_source_id，因此在查询计划中删除了“密钥查找” - 在我们的实现中并不是必需的。
< / LI>

将UPDATE + INSERT重写为单个MERGE声明。

MERGE sync_publishers2 t
USING @ids s
ON s.[value] = t.sync_object_id
    and t.sync_registered_object_type_id = @objectTypeId
WHEN MATCHED
    THEN UPDATE
        SET master_update_date = @date
WHEN NOT MATCHED
    THEN INSERT
             (sync_object_id, sync_registered_object_type_id, master_update_date)
        VALUES
             (s.[value], @objectTypeId, @date);

开始在MERGE语句中遇到死锁。可以在此处查看新的死锁图：http://pastebin.com/QNJk7tea。

更新3.尝试MERGE提示

我尝试使用MERGE和xlock提示进行holdlock - 但没有运气 - 再次在MERGE上陷入僵局。

MERGE sync_publishers2 with(xlock, holdlock) t

Answer 1

这是3个工作负载会话并行1小时后似乎没有死锁的版本。我无法在第一时间找到死锁的确切原因，但我能做的是强调与死锁的区别尝试同时也接受MERGE语句：版本低于（似乎工作正常）使用CTE允许要以仅提及PK列（MERGE）的方式重写ON的{{1}}表达式。

sync_publisher_id

示例执行计划：

将部分触发器提取到存储过程后死锁

1 个答案: