chr*_*_68 5 c# sql-server multithreading deadlock database-deadlocks
我有一种情况，当使用多个线程时，将新记录从 C# ASP.NET Web API 插入 SQL Server 数据库表会导致死锁。这是由初始SELECT获取共享范围锁 (RangeS-S) 引起的，然后在INSERT发生时将其转换为 RangeI-N。
缩写和匿名死锁 XML 如下所示。
<deadlock-list>
<deadlock victim="process19d91c28">
<process-list>
<process id="process19d91c28" taskpriority="0" logused="372" waitresource="KEY: 6:72057594044416000 (ffffffffffff)" waittime="3914" ownerId="1072531" transactionname="user_transaction" lasttranstarted="2015-03-27T15:41:26.670" XDES="0x5faad0d0" lockMode="RangeI-N" schedulerid="3" kpid="4300" status="suspended" spid="58" sbid="0" ecid="0" priority="0" trancount="2" lastbatchstarted="2015-03-27T15:41:26.693" lastbatchcompleted="2015-03-27T15:41:26.693" lastattention="1900-01-01T00:00:00.693" clientapp=".Net SqlClient Data Provider" hostname="MYHOST" hostpid="17300" loginname="MYDOMAIN\XYZ_DB_DEV" isolationlevel="serializable (4)" xactid="1072531" currentdb="6" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
<executionStack>
<frame procname="XYZ_Local.dbo.Article_Insert" line="20" stmtstart="1100" stmtend="2372" sqlhandle="0x0300060049c6306a7d37c200b0a3000001000000000000000000000000000000000000000000000000000000">
INSERT INTO Article (
-- ABREVIATED
) VALUES (
-- ABREVIATED
</frame>
</executionStack>
<inputbuf>
Proc [Database Id = 6 Object Id = 1781581385]
</inputbuf>
</process>
<process id="process3bd3f468" taskpriority="0" logused="372" waitresource="KEY: 6:72057594044416000 (ffffffffffff)" waittime="3916" ownerId="1072527" transactionname="user_transaction" lasttranstarted="2015-03-27T15:41:26.663" XDES="0x5faa73f0" lockMode="RangeI-N" schedulerid="2" kpid="3240" status="suspended" spid="59" sbid="0" ecid="0" priority="0" trancount="2" lastbatchstarted="2015-03-27T15:41:26.690" lastbatchcompleted="2015-03-27T15:41:26.690" lastattention="1900-01-01T00:00:00.690" clientapp=".Net SqlClient Data Provider" hostname="MYHOST" hostpid="17300" loginname="MYDOMAIN\XYZ_DB_DEV" isolationlevel="serializable (4)" xactid="1072527" currentdb="6" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
<executionStack>
<frame procname="XYZ_Local.dbo.Article_Insert" line="20" stmtstart="1100" stmtend="2372" sqlhandle="0x0300060049c6306a7d37c200b0a3000001000000000000000000000000000000000000000000000000000000">
INSERT INTO Article (
-- ABREVIATED
) VALUES (
-- ABREVIATED
</frame>
</executionStack>
<inputbuf>
Proc [Database Id = 6 Object Id = 1781581385]
</inputbuf>
</process>
</process-list>
<resource-list>
<keylock hobtid="72057594044416000" dbid="6" objectname="XYZ_Local.dbo.Article" indexname="IX_Article_THEINDEX" id="lock43227700" mode="RangeS-S" associatedObjectId="72057594044416000">
<owner-list>
<owner id="process3bd3f468" mode="RangeS-S"/>
<owner id="process3bd3f468" mode="RangeI-N" requestType="convert"/>
</owner-list>
<waiter-list>
<waiter id="process19d91c28" mode="RangeI-N" requestType="convert"/>
</waiter-list>
</keylock>
<keylock hobtid="72057594044416000" dbid="6" objectname="XYZ_Local.dbo.Article" indexname="IX_Article_THEINDEX" id="lock43227700" mode="RangeS-S" associatedObjectId="72057594044416000">
<owner-list>
<owner id="process19d91c28" mode="RangeS-S"/>
<owner id="process19d91c28" mode="RangeI-N" requestType="convert"/>
</owner-list>
<waiter-list>
<waiter id="process3bd3f468" mode="RangeI-N" requestType="convert"/>
</waiter-list>
</keylock>
</resource-list>
</deadlock>
</deadlock-list>
添加WITH (UPDLOCK)到初始SELECT“解决”死锁，但它不是很漂亮且有效，与代码中的 lock() 相同，因为它在事务期间阻塞所有其他线程。
添加SET TRANSACTION ISOLATION LEVEL REPEATABLE READ到 Article_Insert SPROC 似乎也解决了僵局。
我从这个 XML 中看到，隔离级别是Serializable，我很困惑这是怎么回事。当我运行此代码时。
SELECT *
FROM [Ecs_Local].[dbo].[Article]
WHERE title ='jcp001'
SELECT CASE transaction_isolation_level
WHEN 0 THEN 'Unspecified'
WHEN 1 THEN 'ReadUncommitted'
WHEN 2 THEN 'ReadCommitted'
WHEN 3 THEN 'Repeatable'
WHEN 4 THEN 'Serializable'
WHEN 5 THEN 'Snapshot' END AS TRANSACTION_ISOLATION_LEVEL
FROM sys.dm_exec_sessions
where session_id = @@SPID
响应是ReadCommitted，因此 SQL Server 实例上的默认值是ReadCommitted。
当我在 c# 代码中构建事务时，我使用了一个执行此操作的实用程序
_transaction = _connection.BeginTransaction(IsolationLevel.Serializable);
我假设这将整个事务的默认隔离级别设置为 Serializable。
我已经研究过重构代码以在事务外进行初始选择，但这并不简单，也不一定能解决也可能遇到此问题的其他代码区域。
我想了解的是解决此问题的最佳方法是什么：
READ COMMITTED（这将适用于我的应用程序中的每个事务）以及潜在的问题是什么（我不明白幻读问题）REPEATABLE READ编辑 1 根据 Bogdan 的要求，这里是匿名执行计划
<?xml version="1.0" encoding="utf-16"?>
<ShowPlanXML xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" Version="1.2" Build="12.0.2000.8" xmlns="http://schemas.microsoft.com/sqlserver/2004/07/showplan">
<BatchSequence>
<Batch>
<Statements>
<StmtSimple StatementCompId="1" StatementId="1" StatementText="Article_Insert" StatementType="EXECUTE PROC" RetrievedFromCache="false" />
</Statements>
<Statements>
<StmtSimple>
<StoredProc ProcName="Article_Insert">
<Statements>
<StmtSimple StatementCompId="2" StatementId="2" StatementText="CREATE PROCEDURE [dbo].[Article_Insert]
 @CurrentUser NVARCHAR(1000),
 @xyzJDocId BIGINT,
 @xyzZDocId BIGINT,
 @ZDocNumber NVARCHAR(255) = NULL,
 @InstutionType NVARCHAR(255),
 @InstutionName NVARCHAR(255) = NULL,
 @QWStatus NVARCHAR(255) = NULL,
 @Doi NVARCHAR(32) = NULL,
 @Title NVARCHAR(4000),
 @ArticleType NVARCHAR(255),
 @Active BIT,
 @Exempt BIT,
 @NewDocRequired BIT
AS
BEGIN
 -- ThirdPartyContent Abc -> xyz only
 -- ConflictOfInterest Abc -> xyz only

 SET TRANSACTION ISOLATION LEVEL REPEATABLE READ

 " StatementType="SET TRANSACTION ISOLATION LEVEL" RetrievedFromCache="true" />
<StmtSimple StatementCompId="3" StatementEstRows="1" StatementId="3" StatementOptmLevel="TRIVIAL" CardinalityEstimationModelVersion="120" StatementSubTreeCost="0.0300044" StatementText="INSERT INTO Article (
 [CreatedDate], 
 [LastModifiedBy],
 [xyzJDocId], 
 [xyzZDocId],
 [ZDocNumber],
 [InstutionType],
 [InstutionName],
 [QWStatus],
 [Doi],
 [Title],
 [ArticleType],
 [Active],
 [Exempt],
 [NewDocRequired]
 ) VALUES (
 GETUTCDATE(),
 @CurrentUser,
 @xyzJDocId,
 @xyzZDocId,
 @ZDocNumber,
 @InstutionType,
 @InstutionName,
 @QWStatus,
 @Doi,
 @Title,
 @ArticleType,
 @Active,
 @Exempt,
 @NewDocRequired
 )" StatementType="INSERT" QueryHash="0x108916B56B42574E" QueryPlanHash="0x73B019D9C6F1A1C5" RetrievedFromCache="true">
<StatementSetOptions ANSI_NULLS="true" ANSI_PADDING="true" ANSI_WARNINGS="true" ARITHABORT="true" CONCAT_NULL_YIELDS_NULL="true" NUMERIC_ROUNDABORT="false" QUOTED_IDENTIFIER="true" />
<QueryPlan CachedPlanSize="32" CompileTime="1" CompileCPU="1" CompileMemory="176">
<MemoryGrantInfo SerialRequiredMemory="0" SerialDesiredMemory="0" />
<OptimizerHardwareDependentProperties EstimatedAvailableMemoryGrant="38400" EstimatedPagesCached="9600" EstimatedAvailableDegreeOfParallelism="2" />
<RelOp AvgRowSize="9" EstimateCPU="3E-06" EstimateIO="0.03" EstimateRebinds="0" EstimateRewinds="0" EstimatedExecutionMode="Row" EstimateRows="1" LogicalOp="Insert" NodeId="0" Parallel="false" PhysicalOp="Clustered Index Insert" EstimatedTotalSubtreeCost="0.0300044">
<OutputList />
<Update DMLRequestSort="false">
<Object Database="[XYZ_Local]" Schema="[dbo]" Table="[Article]" Index="[PK__tmp_ms_x__3214EC071788A4DB]" IndexKind="Clustered" Storage="RowStore" />
<Object Database="[XYZ_Local]" Schema="[dbo]" Table="[Article]" Index="[IX_Article_THEINDEX]" IndexKind="NonClustered" Storage="RowStore" />
<Object Database="[XYZ_Local]" Schema="[dbo]" Table="[Article]" Index="[IX_Article_OTHERINDEX]" IndexKind="NonClustered" Storage="RowStore" />
<SetPredicate>
<ScalarOperator ScalarString="[XYZ_Local].[dbo].[Article].[CreatedDate] = RaiseIfNullInsert([Expr1003]),[XYZ_Local].[dbo].[Article].[LastModifiedBy] = RaiseIfNullInsert([@CurrentUser]),[XYZ_Local].[dbo].[Article].[xyzJDocId] = RaiseIfNullInsert([@xyzJDocId]),[XYZ_Local].[dbo].[Article].[xyzZDocId] = RaiseIfNullInsert([@xyzZDocId]),[XYZ_Local].[dbo].[Article].[ZDocNumber] = [@ZDocNumber],[XYZ_Local].[dbo].[Article].[InstutionType] = [@InstutionType],[XYZ_Local].[dbo].[Article].[InstutionName] = [@InstutionName],[XYZ_Local].[dbo].[Article].[QWStatus] = [@QWStatus],[XYZ_Local].[dbo].[Article].[Doi] = [@Doi],[XYZ_Local].[dbo].[Article].[Title] = RaiseIfNullInsert([@Title]),[XYZ_Local].[dbo].[Article].[ArticleType] = RaiseIfNullInsert([@ArticleType]),[XYZ_Local].[dbo].[Article].[Active] = RaiseIfNullInsert([@Active]),[XYZ_Local].[dbo].[Article].[Exempt] = RaiseIfNullInsert([@Exempt]),[XYZ_Local].[dbo].[Article].[NewDocRequired] = RaiseIfNullInsert([@NewDocRequired]),[XYZ_Local].[dbo].[Article].[Id] = [Expr1002],[XYZ_Local].[dbo].[Article].[ThirdPartyContent] = NULL,[XYZ_Local].[dbo].[Article].[ConflictOfInterest] = NULL">
<ScalarExpressionList>
<ScalarOperator>
<MultipleAssign>
<Assign>
<ColumnReference Database="[XYZ_Local]" Schema="[dbo]" Table="[Article]" Column="CreatedDate" />
<ScalarOperator>
<Intrinsic FunctionName="RaiseIfNullInsert">
<ScalarOperator>
<Identifier>
<ColumnReference Column="Expr1003" />
</Identifier>
</ScalarOperator>
</Intrinsic>
</ScalarOperator>
</Assign>
<Assign>
<ColumnReference Database="[XYZ_Local]" Schema="[dbo]" Table="[Article]" Column="LastModifiedBy" />
<ScalarOperator>
<Intrinsic FunctionName="RaiseIfNullInsert">
<ScalarOperator>
<Identifier>
<ColumnReference Column="@CurrentUser" />
</Identifier>
</ScalarOperator>
</Intrinsic>
</ScalarOperator>
</Assign>
<Assign>
<ColumnReference Database="[XYZ_Local]" Schema="[dbo]" Table="[Article]" Column="xyzJDocId" />
<ScalarOperator>
<Intrinsic FunctionName="RaiseIfNullInsert">
<ScalarOperator>
<Identifier>
<ColumnReference Column="@xyzJDocId" />
</Identifier>
</ScalarOperator>
</Intrinsic>
</ScalarOperator>
</Assign>
<Assign>
<ColumnReference Database="[XYZ_Local]" Schema="[dbo]" Table="[Article]" Column="xyzZDocId" />
<ScalarOperator>
<Intrinsic FunctionName="RaiseIfNullInsert">
<ScalarOperator>
<Identifier>
<ColumnReference Column="@xyzZDocId" />
</Identifier>
</ScalarOperator>
</Intrinsic>
</ScalarOperator>
</Assign>
<Assign>
<ColumnReference Database="[XYZ_Local]" Schema="[dbo]" Table="[Article]" Column="ZDocNumber" />
<ScalarOperator>
<Identifier>
<ColumnReference Column="@ZDocNumber" />
</Identifier>
</ScalarOperator>
</Assign>
<Assign>
<ColumnReference Database="[XYZ_Local]" Schema="[dbo]" Table="[Article]" Column="InstutionType" />
<ScalarOperator>
<Identifier>
<ColumnReference Column="@InstutionType" />
</Identifier>
</ScalarOperator>
</Assign>
<Assign>
<ColumnReference Database="[XYZ_Local]" Schema="[dbo]" Table="[Article]" Column="InstutionName" />
<ScalarOperator>
<Identifier>
<ColumnReference Column="@InstutionName" />
</Identifier>
</ScalarOperator>
</Assign>
<Assign>
<ColumnReference Database="[XYZ_Local]" Schema="[dbo]" Table="[Article]" Column="QWStatus" />
<ScalarOperator>
由于可串行化隔离级别，S 锁由 select 获取。Serialized 的意思是“就像串行执行一样”，在 SQL Server 中，它要求所有读取的数据都是稳定的。
您似乎不需要它，因此您可能应该降低隔离级别。
快照隔离级别通常非常适合许多应用程序。您可以通过读取数据的零锁定和对现有锁的无阻塞来获得完美的读取一致性（此处谈论行锁 - 请将此陈述视为近似信息）。
第 3 点（使用可重复读取）没有帮助，因为您无法减少 DML 所采用的锁定。隔离级别（几乎）没有影响。
请让我知道你在想什么。回答诸如此类的问题总是很困难，因为“最佳”解决方案很大程度上取决于具体情况。如果适用的话，我总是推荐 SI，因为它是解决广泛问题的整体解决方案。