0

我现在有一个关于此问题的简单示例，来自：由于 SQL Server 中的更新冲突，快照隔离事务中止

这是创建数据库表的脚本：

CREATE TABLE [dbo].[tblPPObjectChildObjectList](
    [SortIndex] [int] NOT NULL,
    [UpdateTime] [datetime] NULL,
    [InsertionID] [bigint] NOT NULL,
    [ChildInsertionID] [bigint] NOT NULL,
    [SortText] [nvarchar](260) NULL,
    [UpdateID] [bigint] NULL,
    [RemovalThreshold] [bigint] NULL,
 CONSTRAINT [PK_tblPPObjectChildObjectList] PRIMARY KEY CLUSTERED 
(
    [InsertionID] ASC,
    [ChildInsertionID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 85, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]
GO

CREATE NONCLUSTERED INDEX [IX_tblPPObjectChildObjectList_ChildInsertionID_INC_InsertionID_UpdateID_SortText_SortIndex_UpdateTime_RemovalThreshold] ON [dbo].[tblPPObjectChildObjectList]
(
    [ChildInsertionID] ASC
)
INCLUDE([InsertionID],[UpdateID],[SortText],[SortIndex],[UpdateTime],[RemovalThreshold]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 85, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY]
GO

CREATE NONCLUSTERED INDEX [IX_tblPPObjectChildObjectList_InsertionID_UpdateID_INC_SortText_SortIndex_UpdateTime_RemovalThreshold] ON [dbo].[tblPPObjectChildObjectList]
(
    [InsertionID] ASC,
    [UpdateID] ASC
)
INCLUDE([SortText],[SortIndex],[UpdateTime],[RemovalThreshold]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 85, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY]
GO

CREATE TYPE [dbo].[udtPPChildObjectList] AS TABLE(
    [InsertionId] [bigint] NOT NULL,
    [ChildInsertionId] [bigint] NOT NULL,
    [SortIndex] [int] NULL,
    [UpdateId] [bigint] NULL,
    [SortText] [nvarchar](260) NULL,
    [RemovalThreshold] [bigint] NULL,
    PRIMARY KEY CLUSTERED 
(
    [ChildInsertionId] ASC
)WITH (IGNORE_DUP_KEY = OFF)
)
GO

CREATE TYPE [dbo].[udtPPInsertionIDList] AS TABLE(
    [InsertionID] [bigint] NOT NULL,
    PRIMARY KEY CLUSTERED 
(
    [InsertionID] ASC
)WITH (IGNORE_DUP_KEY = OFF)
)
GO

必须在数据库中打开快照隔离，并且必须打开已提交读快照。

此脚本应用于填充表：

declare @i int
set @i = 1

while (@i < 200)
begin

    insert into [dbo].[tblPPObjectChildObjectList]
    select -1, GetUTCDate(), @i, @i * 1000, null, 1, null

    set @i = @i + 1

end
GO

然后有两个必须同时运行的脚本。这是更新脚本：

SET TRANSACTION ISOLATION LEVEL READ COMMITTED
GO 

declare @insertionid bigint
set @insertionid = 1

while (1 = 1)
begin

    BEGIN TRY
     
        BEGIN TRANSACTION;  

        WAITFOR DELAY '00:00:01';

        declare @updatetime datetime
        set @updatetime = GetUTCDate()

        declare @values dbo.udtPPChildObjectList
        delete from @values

        insert into @values select 1, 1000, -1, 1, null, null
        insert into @values select 2, 2000, -1, 1, null, null
        insert into @values select 3, 3000, -1, 1, null, null
        insert into @values select 4, 4000, -1, 1, null, null
        insert into @values select 5, 5000, -1, 1, null, null
        insert into @values select 6, 6000, -1, 1, null, null
        insert into @values select 7, 7000, -1, 1, null, null
        insert into @values select 8, 8000, -1, 1, null, null
        insert into @values select 9, 9000, -1, 1, null, null
        insert into @values select 10, 10000, -1, 1, null, null
                    
        update t 
        set t.UpdateTime = @updatetime
        from tblPPObjectChildObjectList as t 
        join @values as s
        on s.ChildInsertionId = t.ChildInsertionID

        select t.ChildInsertionID
        from tblPPObjectChildObjectList as t with (updlock, rowlock) 
        left join @values as s
        on s.InsertionId = t.InsertionID and s.ChildInsertionId = t.ChildInsertionID
        where (t.InsertionID in (select InsertionId from @values)) and (s.ChildInsertionId is null)

        COMMIT TRANSACTION; 

    END TRY
    BEGIN CATCH 

        ROLLBACK TRANSACTION;

        print 'ERROR :' + ERROR_MESSAGE()
        break;

    END CATCH

end 
GO

这是删除脚本：

SET TRANSACTION ISOLATION LEVEL SNAPSHOT
GO  

while (1 = 1)
begin

    BEGIN TRY

        WAITFOR DELAY '00:00:01';

        declare @insertionids dbo.udtPPInsertionIDList

        declare @i int
        set @i = 1

        while (@i < 150)
        begin

            insert into @insertionids
            select 90000000 + @i

            set @i = @i + 1

        end

        set deadlock_priority low
        set nocount on

        -- Create the required temporary tables
        declare @LocalInsertionIDs table (InsertionID bigint, PRIMARY KEY (InsertionID))
        
        delete from @LocalInsertionIDs
        insert into @LocalInsertionIDs 
        select InsertionID from @insertionids

        if ((select count(*) from @LocalInsertionIDs) > 0)
        begin
        
            declare @c4 int
            select @c4 = count(*) 
            from tblPPObjectChildObjectList as pocol
            join @LocalInsertionIDs as ii
            on pocol.InsertionID = ii.InsertionID

            delete from pocol with (rowlock, updlock) 
            from tblPPObjectChildObjectList as pocol with (rowlock, updlock) 
            join @LocalInsertionIDs as ii
            on pocol.InsertionID = ii.InsertionID
            
            declare @c5 int
            select @c5 = count(*) 
            from tblPPObjectChildObjectList as pocol
            join @LocalInsertionIDs as ii
            on pocol.ChildInsertionID = ii.InsertionID

            delete from pocol with (rowlock, updlock) 
            from tblPPObjectChildObjectList as pocol with (rowlock, updlock) 
            join @LocalInsertionIDs as ii
            on pocol.ChildInsertionID = ii.InsertionID

        end

        delete from @insertionids

    END TRY
    BEGIN CATCH 
        
        print 'ERROR :' + ERROR_MESSAGE()
        break;

    END CATCH

end
GO

10-15 分钟后，删除脚本将因更新错误而失败，即使被删除的行没有被更新（实际上它们甚至不存在）。

谁能看到为什么会引发这个异常？

4

1 回答 1

0

10-15 分钟后，删除脚本将失败并出现更新错误，即使要删除的行没有被插入或更新。

下面获取要删除的行的查询执行tblPPObjectBlobProperty表的完整扫描，因为在 上不存在索引UpdateTime。当UPDLOCK访问要删除的范围之外的行并且该行已被另一个事务修改时，锁定将失败。

    insert into @InsertionIDs               
    select distinct InsertionID, UpdateTime from tblPPObjectBlobProperty as poco with (rowlock, updlock) 
    where UpdateTime < @thresholddatetime

在列上添加索引，UpdateTime以便仅触及要删除的行。这应该避免更新冲突错误。

CREATE INDEX idx_tblPPObjectBlobProperty_UpdateTime ON dbo.tblPPObjectBlobProperty(UpdateTime);

附带说明一下，我建议您使用它THROW来促进故障排除。错误消息将包括脚本中问题陈述的行号。此外，SET XACT_ABORT ON;使用显式事务添加到脚本/过程中，以确保事务在错误、客户端超时或查询取消后立即回滚。下面是我使用的标准 catch 块。

BEGIN CATCH 

    IF @@TRANCOUNT > 0 ROLLBACK TRANSACTION;
    THROW;

END CATCH;
于 2022-01-16T12:33:21.457 回答