Jam*_*s D 6 sql-server deadlock identity isolation-level
继承的死锁问题需要帮助！
下面给出的代码似乎已经写了一段时间，试图解决围绕在更大/更胖的 [IDs] 父表上分配新 ID 值的争用问题，首先在较小的 [ID_Stub ] 桌子。然而，持续死锁的存在表明这段代码引起的问题似乎比它解决的问题要多。
我们经常在下表中的 INSERT 语句周围遇到死锁（表名和列名已被混淆）。该表没有触发器或外键依赖项，但具有如下聚簇索引和非聚簇索引。
CREATE TABLE dbo.ID_Stub (
ID int IDENTITY(1,1) NOT NULL,
IDReference nchar(25) NULL,
AdditionalID int NULL,
CreatedBy int NOT NULL,
CreatedOn datetime NOT NULL,
CONSTRAINT PK_ID_Stub PRIMARY KEY CLUSTERED (ID) WITH
(
PAD_INDEX = OFF,
STATISTICS_NORECOMPUTE = OFF,
SORT_IN_TEMPDB = OFF,
IGNORE_DUP_KEY = OFF,
ONLINE = OFF,
ALLOW_ROW_LOCKS = ON,
ALLOW_PAGE_LOCKS = ON,
FILLFACTOR = 90
)
);
GO
CREATE NONCLUSTERED INDEX idx_IDReference ON dbo.ID_Stub (IDReference) 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 = 70
);
GO
该表在任何时候平均包含大约 70,000 行（一个进程运行以每晚修剪记录数）。
默认的实例事务隔离级别是 READ COMMITTED，但是这与隐式事务一起被覆盖（在发生死锁的存储过程中）为 SERIALIZABLE。不幸的是，现阶段我们不能考虑转向优化锁定策略，例如 RCSI。
为了完整起见，下面给出了整个隐式事务，但死锁发生在 ID_Stub 上的最终 INSERT 语句附近。
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;
BEGIN TRANSACTION
-- If a reference has been provided...
IF ISNULL(@IDReference, '') > ''
BEGIN
IF @ID IS NULL
BEGIN
-- Attempt to locate record based on provided reference.
SELECT @ID = MAX(ID)
FROM dbo.IDs I
WHERE I.IDReference = LTRIM(RTRIM(@IDReference))
AND I.CreatedBy = @CreatedBy
AND I.AdditionalID = @AdditionalID
IF @ID IS NULL
BEGIN
-- If there is no corresponding record, the subsequent ID creation after the stub failed.
SET @OriginallyCreated =
(
SELECT MAX(CreatedOn)
FROM dbo.ID_Stub IDS
WHERE IDS.IDReference = LTRIM(RTRIM(@IDReference))
AND IDS.CreatedBy = @CreatedBy
AND IDS.AdditionalID = @AdditionalID
);
-- Delete the stub record if created more than 90 seconds ago.
IF @OriginallyCreated IS NOT NULL
BEGIN
IF DATEDIFF(s, @OriginallyCreated, GETDATE()) < 90
SELECT @FailureMessage = 'The ID for reference ' + RTRIM(@IDReference) + ' is still being processed. Please try later.';
ELSE
DELETE dbo.ID_Stub
WHERE IDReference = LTRIM(RTRIM(@IDReference))
AND CreatedBy = @CreatedBy
AND AdditionalID = @AdditionalID;
END
END
END
ELSE
BEGIN
IF NOT EXISTS
(
SELECT ID
FROM dbo.IDs I
WHERE I.ID = @ID
AND I.CreatedBy = @CreatedBy
)
SELECT @FailureMessage = 'You have no record stored against the supplied ID (' + RTRIM(CONVERT(Char, @ID)) + ')';
ELSE
IF NOT EXISTS
(
SELECT ID
FROM dbo.IDs I
WHERE I.ID = @ID
AND I.IDReference = @IDReference
AND I.CreatedBy = @CreatedBy
)
SELECT @FailureMessage = 'The ID does not match the reference you supplied.';
END
END
ELSE -- No ID Reference provided.
BEGIN
IF @ID IS NOT NULL
BEGIN
IF NOT EXISTS
(
SELECT ID
FROM dbo.IDs I
WHERE I.ID = @ID
AND I.CreatedBy = @CreatedBy
)
SELECT @FailureMessage = 'You have no record stored against the supplied ID (' + RTRIM(CONVERT(Char, @ID)) + ').';
END
END
IF @FailureMessage <> ''
BEGIN
ROLLBACK;
RETURN 1;
END
-- If it's a new submission, create a stub for it.
IF @ID IS NULL
BEGIN
INSERT dbo.ID_Stub (IDReference, AdditionalID, CreatedBy, CreatedOn)
VALUES (@IDReference, @AdditionalID, @CreatedBy, GETDATE());
SELECT @ID = SCOPE_IDENTITY();
END
COMMIT
SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
XML死锁报告如下。
<deadlock>
<victim-list>
<victimProcess id="process1e7fd5d8108"/>
</victim-list>
<process-list>
<process id="process1e7fd5d8108" taskpriority="0" logused="336" waitresource="KEY: 30:72057596372844544 (4f8ff66d381b)" waittime="4265" ownerId="1879373839" transactionname="user_transaction" lasttranstarted="2018-12-29T22:19:51.357" XDES="0x1dfe81c9538" lockMode="RangeI-N" schedulerid="6" kpid="2084" status="suspended" spid="182" sbid="0" ecid="0" priority="0" trancount="2" lastbatchstarted="2018-12-29T22:19:51.307" lastbatchcompleted="2018-12-29T22:19:51.293" lastattention="1900-01-01T00:00:00.293" clientapp=".Net SqlClient Data Provider" hostname="<obfuscated>" hostpid="3648" loginname="<obfuscated>" isolationlevel="serializable (4)" xactid="1879373839" currentdb="30" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
<executionStack>
<frame procname="<obfuscated>" line="640" stmtstart="68006" stmtend="68296" sqlhandle="0x03001e002acd7f07eca57a012ea9000001000000000000000000000000000000000000000000000000000000"> INSERT dbo.ID_Stub (IDReference, AdditionalID, CreatedBy, CreatedOn) VALUES (@IDReference, @AdditionalID, @CreatedBy, GETDATE(); </frame>
</executionStack>
<inputbuf> Proc [Database Id = 30 Object Id = 125816106] </inputbuf>
</process>
<process id="process1fd327c7c28" taskpriority="0" logused="336" waitresource="KEY: 30:72057596372844544 (4f8ff66d381b)" waittime="4265" ownerId="1879373837" transactionname="user_transaction" lasttranstarted="2018-12-29T22:19:51.357" XDES="0x1e76d97ebd8" lockMode="RangeI-N" schedulerid="3" kpid="9084" status="suspended" spid="208" sbid="0" ecid="0" priority="0" trancount="2" lastbatchstarted="2018-12-29T22:19:51.300" lastbatchcompleted="2018-12-29T22:19:51.293" lastattention="1900-01-01T00:00:00.293" clientapp=".Net SqlClient Data Provider" hostname="<obfuscated>" hostpid="3648" loginname="<obfuscated>" isolationlevel="serializable (4)" xactid="1879373837" currentdb="30" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
<executionStack>
<frame procname="<obfuscated>" line="640" stmtstart="68006" stmtend="68296" sqlhandle="0x03001e002acd7f07eca57a012ea9000001000000000000000000000000000000000000000000000000000000"> INSERT dbo.ID_Stub (IDReference, AdditionalID, CreatedBy, CreatedOn) VALUES (@IDReference, @AdditionalID, @CreatedBy, GETDATE(); </frame>
</executionStack>
<inputbuf> Proc [Database Id = 30 Object Id = 125816106] </inputbuf>
</process>
</process-list>
<resource-list>
<keylock hobtid="72057596372844544" dbid="30" objectname="<obfuscated>.<obfuscated>.ID_Stub" indexname="idx_IDReference" id="lock1e566d4a380" mode="RangeS-S" associatedObjectId="72057596372844544">
<owner-list>
<owner id="process1fd327c7c28" mode="RangeS-S"/>
<owner id="process1fd327c7c28" mode="RangeI-N" requestType="convert"/>
</owner-list>
<waiter-list>
<waiter id="process1e7fd5d8108" mode="RangeI-N" requestType="convert"/>
</waiter-list>
</keylock>
<keylock hobtid="72057596372844544" dbid="30" objectname="<obfuscated>.<obfuscated>.ID_Stub" indexname="idx_IDReference" id="lock1e566d4a380" mode="RangeS-S" associatedObjectId="72057596372844544">
<owner-list>
<owner id="process1e7fd5d8108" mode="RangeS-S"/>
<owner id="process1e7fd5d8108" mode="RangeI-N" requestType="convert"/>
</owner-list>
<waiter-list>
<waiter id="process1fd327c7c28" mode="RangeI-N" requestType="convert"/>
</waiter-list>
</keylock>
</resource-list>
</deadlock>
第一条语句的查询计划可以在下面的链接中找到。
https://www.brentozar.com/pastetheplan/?id=BkVfC8qbN
任何关于如何最好地解决这些僵局的提示或建议将不胜感激。
我们经常在下表中的 INSERT 语句周围遇到死锁……发生死锁的存储过程 [使用] SERIALIZABLE
是的。这是 SERIALIZABLE 隔离级别的预期行为。它没有被广泛理解，但死锁是 SERIALIZABLE 强制隔离级别的方式。它不会阻止并发会话尝试写入冲突的更改；如果两个会话读取数据，然后都尝试发生冲突的更改，则会发生死锁，并且只有一次写入成功。
因此，如果您不想处理死锁，那么您使用了错误的并发模型。
如果你只是想阻止这个事务的并发执行，强制会话一次执行一个，最简单的方法是使用应用程序锁：
BEGIN TRANSACTION
exec sp_getapplock @Resource = 'MyTransaction', @LockMode = 'Exclusive';
. . .