第一笔交易完成后，第二笔交易仍在等待中

Question

在SSMS的2个窗口中一次又一次地延迟运行同一脚本。
我稍后启动的第二个实例完成，但是第一个实例保持锁定状态，直到我关闭第二个窗口。 这是怎么回事 为什么在COMMIT之后不释放锁？

SET TRAN ISOLATION LEVEL SERIALIZABLE
BEGIN TRAN

SELECT * FROM dbo.t1
WHERE id IN (1,3)

WAITFOR DELAY '00:00:20'

UPDATE t1 SET InUse=0
WHERE id IN (1,3)

COMMIT

编辑：

表结构如下：

CREATE TABLE [dbo].[t1](
    [id] [INT] NOT NULL,
    [InUse] [BIT] NOT NULL DEFAULT ((0)),
PRIMARY KEY CLUSTERED 
(
    [id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

Answer 1

您应该使用表结构更新您的问题。

由于您没有指定表是否具有索引，所以我假设它没有索引，即dbo.t1是heap 。

在这种情况下，您将获得经典的deadlock ：

session1希望从表中进行select ，并且需要S来读取它的任何行，并且因为dbo.t1上没有index ， dbo.t1整个表都被读取，并且在事务的整个持续时间内，表上的S-lock被保留。

同时， session2会执行相同的操作，并且还会在表上获取S-lock并将其保存。

Session1现在需要将其转换成S-lock到IX为了做update ，它是通过阻断session2持有S上dbo.t1 。

当session2尝试执行相同操作时，这将导致死锁，因为两个会话都需要IX并且都被另一个会话锁定。

这是相应的死锁图：

deadlock-list
 deadlock victim=process155d1d498
  process-list
   process id=process155d1d498 taskpriority=0 logused=0 waitresource=OBJECT: 26:1765581328:0  waittime=16222 ownerId=5528849 transactionname=user_transaction lasttranstarted=2019-02-07T13:39:38.837 XDES=0x15ec1c3a8 lockMode=IX schedulerid=4 kpid=8140 status=suspended spid=54 sbid=0 ecid=0 priority=0 trancount=2 lastbatchstarted=2019-02-07T13:39:38.833 lastbatchcompleted=2019-02-07T13:39:38.833 lastattention=2019-02-07T13:38:49.187 clientapp=Microsoft SQL Server Management Studio - Query hostname=pppp hostpid=12276 loginname=FINCONSGROUP\anna.savchenko isolationlevel=serializable (4) xactid=5528849 currentdb=26 lockTimeout=4294967295 clientoption1=671098976 clientoption2=390200
    executionStack
     frame procname=adhoc line=9 stmtstart=248 stmtend=334 sqlhandle=0x02000000f445021276fec0f5ec119082f65611ce316a4d280000000000000000000000000000000000000000
UPDATE t1 SET InUse=0
WHERE id IN (1,3)     
    inputbuf
SET TRAN ISOLATION LEVEL SERIALIZABLE
BEGIN TRAN
SELECT * FROM dbo.t1
WHERE id IN (1,3)
WAITFOR DELAY '00:00:20'
UPDATE t1 SET InUse=0
WHERE id IN (1,3)
COMMIT
   process id=process15649f868 taskpriority=0 logused=0 waitresource=OBJECT: 26:1765581328:0  waittime=1212 ownerId=5529084 transactionname=user_transaction lasttranstarted=2019-02-07T13:39:53.847 XDES=0x15ec1d048 lockMode=IX schedulerid=3 kpid=15516 status=suspended spid=57 sbid=0 ecid=0 priority=0 trancount=2 lastbatchstarted=2019-02-07T13:39:53.847 lastbatchcompleted=2019-02-07T13:39:53.847 lastattention=1900-01-01T00:00:00.847 clientapp=Microsoft SQL Server Management Studio - Query hostname=pppp hostpid=12276 loginname=FINCONSGROUP\anna.savchenko isolationlevel=serializable (4) xactid=5529084 currentdb=26 lockTimeout=4294967295 clientoption1=671098976 clientoption2=390200
    executionStack
     frame procname=adhoc line=9 stmtstart=248 stmtend=334 sqlhandle=0x0200000093b3ba1c08d586d1f142f473a7c8996074a369fc0000000000000000000000000000000000000000
UPDATE t1 SET InUse=0
WHERE id IN (1,3)     
    inputbuf
SET TRAN ISOLATION LEVEL SERIALIZABLE
BEGIN TRAN
SELECT * FROM dbo.t1
WHERE id IN (1,3)
WAITFOR DELAY '00:00:20'
UPDATE t1 SET InUse=0
WHERE id IN (1,3)
COMMIT    
  resource-list
   objectlock lockPartition=0 objid=1765581328 subresource=FULL dbid=26 objectname=parts.dbo.t1 id=lock152c2d300 mode=S associatedObjectId=1765581328
    owner-list
     owner id=process15649f868 mode=S
     owner id=process15649f868 mode=IX requestType=convert
    waiter-list
     waiter id=process155d1d498 mode=IX requestType=convert
   objectlock lockPartition=0 objid=1765581328 subresource=FULL dbid=26 objectname=parts.dbo.t1 id=lock152c2d300 mode=S associatedObjectId=1765581328
    owner-list
     owner id=process155d1d498 mode=S
     owner id=process155d1d498 mode=IX requestType=convert
    waiter-list
     waiter id=process15649f868 mode=IX requestType=convert