ML.Net Model Builder训练时出现'SQL关键字Open附近语法错误'

• 工具链：Visual Studio 2019，内置ML.NET Model Builder版本16.3.0.2056001
• 项目配置：.Net 5.0目标框架，由官方脚手架自动生成的标准空项目
• 复现流程：
  1. 新建项目后启动Model Builder向导，依次选择「添加 > 机器学习 > 连接到SQL Server」
  2. 完成数据库连接配置后，连通性测试正常，数据表预览可正确加载字段和内容
  3. 进入训练配置页面，点击「开始训练」后触发运行时错误
• 核心错误提示：Incorrect syntax near the keyword 'Open'
• 堆栈跟踪：

at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
at System.Data.SqlClient.SqlDataReader.TryConsumeMetaData()
at System.Data.SqlClient.SqlDataReader.get_MetaData()
at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString, Boolean isInternal, Boolean forDescribeParameterEncryption, Boolean shouldCacheForAlwaysEncrypted)
at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async, Int32 timeout, Task& task, Boolean asyncWrite, Boolean inRetry, SqlDataReader ds, Boolean describeParameterEncryptionRequest)
at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry)
at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)
at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)
at Microsoft.ML.Data.DatabaseLoader.Cursor.get_DataReader()
at Microsoft.ML.Data.DatabaseLoader.Cursor.MoveNextCore()
at Microsoft.ML.Data.RootCursorBase.MoveNext()
at Microsoft.ML.AutoML.DatasetDimensionsUtil.CountRows(IDataView data, UInt64 maxRows)
at Microsoft.ML.AutoML.ExperimentBase`2.Execute(IDataView trainData, ColumnInformation columnInformation, IEstimator`1 preFeaturizer, IProgress`1 progressHandler)
at Microsoft.ML.ModelBuilder.AutoMLService.Experiments.AutoMLExperiment`3.<>c__DisplayClass21_0.<b__5>d.MoveNext() in //src/Microsoft.ML.ModelBuilder.AutoMLService/Experiments/AutoMLExperiment.cs:line 80
at System.Threading.Tasks.Task`1.InnerInvoke()
at System.Threading.Tasks.Task.Execute()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.ML.ModelBuilder.AutoMLService.Experiments.AutoMLExperiment`3.<ExecuteExperimentAsync>d__21.MoveNext() in //src/Microsoft.ML.ModelBuilder.AutoMLService/Experiments/AutoMLExperiment.cs:line 107
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.ML.ModelBuilder.AutoMLEngine.<RunAsync>d__26.MoveNext() in /_/src/Microsoft.ML.ModelBuilder.AutoMLService/AutoMLEngineService/AutoMLEngine.cs:line 150

• 已尝试的排查操作：在项目中手动添加Microsoft.ML 1.5.4、Microsoft.ML.Experimental 0.17.4NuGet包，项目csproj配置如下：

<Project Sdk="Microsoft.NET.Sdk.Web">
  <PropertyGroup>
    <TargetFramework>net5.0</TargetFramework>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.ML" Version="1.5.4" />
    <PackageReference Include="Microsoft.ML.Experimental" Version="0.17.4" />
  </ItemGroup>
</Project>

这是对应版本Model Builder的内置Bug，和你的数据库配置、项目代码完全无关：

• 16.3.0.2056001版本的Model Builder内置DatabaseLoader组件，生成SQL Server查询语句时存在硬编码错误：本来应该写SELECT * FROM 你的表名，结果它在表名前面多拼了个Open关键字，生成的SQL完全不符合T-SQL语法规范，SQL Server执行到这段错误语句时，就会抛出“关键字Open附近有语法错误”的提示。
• 手动加NuGet包的操作完全没用：因为Model Builder训练流程调用的是扩展自身内置的ML.NET运行时，根本不会读取你项目里手动引用的ML.NET包版本，自然也覆盖不了组件本身的错误逻辑。

• 绕开自动生成SQL的逻辑：在Model Builder的SQL Server数据源配置页，不要直接选择现成的数据表，切换到「自定义SQL查询」选项，手动写符合规范的查询语句（比如SELECT * FROM [你的架构名].[你的表名]），从根源上避开组件生成的错误SQL。
• 升级Model Builder扩展：在Visual Studio的扩展管理面板，把ML.NET Model Builder升级到16.8及以上版本，这个版本已经修复了DatabaseLoader的SQL拼接Bug，完全兼容.Net 5.0项目。
• 临时替代方案：如果暂时没法升级扩展，可以先把目标数据表导出为CSV格式文件，选择Model Builder的「本地文件数据源」导入数据完成全流程训练，等后续升级了扩展再切回直连数据库的模式。

内容的提问来源于stack exchange，提问作者Holland Risley