Question

虽然我无法透露有关真实表格的信息（如果我可以，但我会）导致上一个问题中描述的问题，我从头开始构建了一个（非）工作示例，它准确地再现了数据类型 - 类型，列大小按列大小）我面临的问题。所以我创建了一个名为“QueueTest”的新数据库并运行以下脚本：

CREATE TABLE Request
(
    RequestID   BIGINT PRIMARY KEY,
    Priority    TINYINT,
    DateEntered DATETIME
)

CREATE TABLE Options
(
    RequestIDRef    BIGINT PRIMARY KEY,
    SomeOptions     NVARCHAR(MAX)
)

ALTER TABLE Options ADD

    CONSTRAINT FK_REQUESTIDREF FOREIGN KEY ( RequestIDRef ) REFERENCES [Request] ( RequestID )

GO

INSERT INTO Request VALUES ( 1, 2, GETDATE() )
INSERT INTO Request VALUES ( 2, 1, GETDATE() )
INSERT INTO Request VALUES ( 3, 3, GETDATE() )
INSERT INTO Request VALUES ( 4, 2, GETDATE() )

INSERT INTO Options VALUES ( 1, 'Options1' )
INSERT INTO Options VALUES ( 2, 'Options2' )
INSERT INTO Options VALUES ( 3, 'Options3' )
INSERT INTO Options VALUES ( 4, 'Options4' )

CREATE NONCLUSTERED INDEX IX_OPTIONS_REQUESTIDREF ON [Options] ( RequestIDRef )
CREATE NONCLUSTERED INDEX IX_REQUEST_PRIORITY_DATEENTERED ON [Request] ( Priority , DateEntered ) INCLUDE ( RequestID )

之后我打开了两个新查询Query1和Query2，并运行以下脚本来模拟问题：

BEGIN TRANSACTION

SELECT TOP 2 RequestID FROM ( Request R WITH ( ROWLOCK , UPDLOCK , READPAST ) INNER JOIN Options O WITH ( ROWLOCK , UPDLOCK , READPAST ) ON ( R.RequestID = O.RequestIDRef ) ) ORDER BY Priority ASC , DateEntered ASC

WAITFOR DELAY '00:00:02.500'

COMMIT TRANSACTION

我得到的结果是

Query1 | Query 2
   2   |
   1   |

当然，我当时正在等待

Query1 | Query 2
   2   |    4
   1   |    3

所以，我假设即使我有上述索引，Query1仍然锁定整个表。以下是两个查询的执行计划：

执行计划

StmtText
-----------------------
SET SHOWPLAN_TEXT ON

(1 row(s) affected)

StmtText
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

BEGIN TRANSACTION

SELECT TOP 2 RequestID FROM ( Request R WITH ( ROWLOCK , UPDLOCK , READPAST ) INNER JOIN Options O WITH ( ROWLOCK , UPDLOCK , READPAST ) ON ( R.RequestID = O.RequestIDRef ) ) ORDER BY Priority ASC , DateEntered ASC

(2 row(s) affected)

StmtText
------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  |--Top(TOP EXPRESSION:((2)))
       |--Nested Loops(Inner Join, WHERE:([QueueTest].[dbo].[Options].[RequestIDRef] as [O].[RequestIDRef]=[QueueTest].[dbo].[Request].[RequestID] as [R].[RequestID]))
            |--Index Scan(OBJECT:([QueueTest].[dbo].[Request].[IX_REQUEST_PRIORITY_DATEENTERED] AS [R]), ORDERED FORWARD)
            |--Clustered Index Scan(OBJECT:([QueueTest].[dbo].[Options].[PK__Options__5366EEE80BC6C43E] AS [O]))

(4 row(s) affected)

StmtText
---------------------------------

WAITFOR DELAY '00:00:02.500'

COMMIT TRANSACTION

(2 row(s) affected)

请注意，当我使用SET SHOWPLAN_TEXT ON运行两个查询时，我认为WAITFOR DELAY指令未得到遵守 - 事实上，第一个查询立即完成，所以当我运行第二个查询时它已经完成。

导致锁定问题的原因是什么？请帮助我，因为我自己无法想象它。

修改：请注意，我无法使用SELECT TOP 2指令创建视图。这里的2仅用于说明目的，而在实际情况下，它是传递给存储过程的参数，然后运行此SELECT。另请注意，使用

创建索引视图

SET QUOTED_IDENTIFIER ON
GO

ALTER VIEW TestView WITH SCHEMABINDING AS

    SELECT RequestID , Priority , DateEntered FROM( dbo.Request R INNER JOIN dbo.Options O ON ( R.RequestID = O.RequestIDRef ) )

GO

CREATE UNIQUE CLUSTERED INDEX IX_TESTE_1 ON TestView ( RequestID )
CREATE NONCLUSTERED INDEX IX_TESTE_2 ON TestView ( Priority ASC , DateEntered ASC ) INCLUDE ( RequestID )

然后从TestView WITH ( ROWLOCK , UPDLOCK , READPAST )中选择也不起作用，无论有没有ORDER BY子句。

Answer 1

你有一个“聚集索引扫描”和一个“索引扫描”，它阻止了两个表中的所有行正如我在之前的回答中所说的那样。

同样来自之前的答案：

使用索引视图
视图

调用视图时添加NOEXPAND提示

最后，索引IX_REQUEST_PRIORITY_DATEENTERED没有JOIN条件。这可能会删除其中一个扫描

如果你不听上面的“查看”位，那么试试这两个

CREATE NONCLUSTERED INDEX IX_REQUEST_PRIORITY_DATEENTERED ON [Request] (RequestID , Priority , DateEntered ) CREATE NONCLUSTERED INDEX IX_REQUEST_PRIORITY_DATEENTERED ON [Request] (Priority , DateEntered , RequestID )

ORDER BY和UPDLOCK-A（非）工作示例

1 个答案: