我一直在尝试将我们的 EF6 项目移植到 EF-Core-2.0。
在 EF6 中，我们使用 DbNolock 拦截器来添加 With (NOLOCK) 提示我们需要哪些查询。您可以在下面找到我之前运行的 Db 拦截器代码。
public class DbNoLockInterceptor : DbCommandInterceptor
{
private static readonly Regex TableAliasRegex = new Regex(@"((?<!\){1,5})AS \[Extent\d+\](?! WITH \(NOLOCK\)))", RegexOptions.Multiline | RegexOptions.IgnoreCase);
public override void ScalarExecuting(DbCommand command,
DbCommandInterceptionContext<object> interceptionContext)
{
command.CommandText =
TableAliasRegex.Replace(command.CommandText, mt => mt.Groups[0].Value + " WITH (NOLOCK) ");
}
public override void ReaderExecuting(DbCommand command, DbCommandInterceptionContext<DbDataReader> interceptionContext)
{
command.CommandText = TableAliasRegex.Replace(command.CommandText, mt => mt.Groups[0].Value + " WITH (NOLOCK) ");
}
}
在 Ef-Core 中，我们可以用几乎相同的方式进行拦截。但是由于更改表的命名约定，我无法为新表编写正则表达式。您可以在下面找到新的 Ef-Core 版本:
public class DbNoLockListener
{
private static readonly Regex TableAliasRegex = new Regex(@"((?<!\){1,5})AS \[Extent\d+\](?! WITH \(NOLOCK\)))", RegexOptions.Multiline | RegexOptions.IgnoreCase);
[DiagnosticName("Microsoft.EntityFrameworkCore.Database.Command.CommandExecuting")]
public void OnCommandExecuting(DbCommand command, DbCommandMethod executeMethod, Guid commandId, Guid connectionId, bool async, DateTimeOffset startTime)
{
command.CommandText =
TableAliasRegex.Replace(command.CommandText, mt => mt.Groups[0].Value + " WITH (NOLOCK) ");
}
}
Ef6 生成的 SQL:
SELECT
[Extent1].[Id] AS [Extent1Id],
[Extent2].[Id] AS [Extent2Id]
FROM [Advert].[Advert] AS [Extent1]
INNER JOIN [Membership].[Members] AS [Extent2] ON [Extent1].[MemberId] = [Extent2].[MemberId]
Ef-Core 生成的 SQL:
SELECT
[t].[Id]
,[t.Member].[Id]
FROM [Advert].[Advert] AS [t]
INNER JOIN [Membership].[Members] AS [t.Member] ON [t].[MemberId] = [t.Member].[MemberId]
你也可以看看this github issue for more detail .
我要换 AS [t] 与 AS [t] WITH (NOLOCK) 和 AS [t.Member] 与 AS [t.Member] WITH (NOLOCK)
我可以使用哪种模式在 Ef-Core 中执行相同的操作？
最佳答案
这种拦截方式我看不太好。 IMO 更好的方法是连接到 EF Core 基础设施以替换 IQuerySqlGenerator SqlServer 的服务实现，自定义实现覆盖 VisitTable 方法，如下所示:
public override Expression VisitTable(TableExpression tableExpression)
{
// base will append schema, table and alias
var result = base.VisitTable(tableExpression);
Sql.Append(" WITH (NOLOCK)");
return result;
}
Hook 有点复杂，因为我们需要创建和替换“工厂”服务，以便能够替换 sql 生成器。所有这些的完整代码以及辅助扩展方法如下:
EF 核心 7.0:
using System.Linq.Expressions;
using Microsoft.EntityFrameworkCore.Query;
using Microsoft.EntityFrameworkCore.SqlServer.Query.Sql.Internal;
using Microsoft.EntityFrameworkCore.SqlServer.Query.Internal;
using Microsoft.EntityFrameworkCore.Query.SqlExpressions;
using Microsoft.EntityFrameworkCore.Storage;
namespace Microsoft.EntityFrameworkCore
{
public static partial class CustomDbContextOptionsBuilderExtensions
{
public static DbContextOptionsBuilder UseCustomSqlServerQuerySqlGenerator(this DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.ReplaceService<IQuerySqlGeneratorFactory, CustomSqlServerQuerySqlGeneratorFactory>();
return optionsBuilder;
}
}
}
namespace Microsoft.EntityFrameworkCore.SqlServer.Query.Sql.Internal
{
class CustomSqlServerQuerySqlGeneratorFactory : IQuerySqlGeneratorFactory
{
public CustomSqlServerQuerySqlGeneratorFactory(QuerySqlGeneratorDependencies dependencies, IRelationalTypeMappingSource typeMappingSource)
=> (Dependencies, TypeMappingSource) = (dependencies, typeMappingSource);
public QuerySqlGeneratorDependencies Dependencies { get; }
public IRelationalTypeMappingSource TypeMappingSource { get; }
public QuerySqlGenerator Create() => new CustomSqlServerQuerySqlGenerator(Dependencies, TypeMappingSource);
}
public class CustomSqlServerQuerySqlGenerator : SqlServerQuerySqlGenerator
{
public CustomSqlServerQuerySqlGenerator(QuerySqlGeneratorDependencies dependencies, IRelationalTypeMappingSource typeMappingSource)
: base(dependencies, typeMappingSource) { }
protected override Expression VisitTable(TableExpression tableExpression)
{
// base will append schema, table and alias
var result = base.VisitTable(tableExpression);
Sql.Append(" WITH (NOLOCK)");
return result;
}
}
}
EF 核心 3.x:
using System.Linq.Expressions;
using Microsoft.EntityFrameworkCore.Query;
using Microsoft.EntityFrameworkCore.SqlServer.Query.Sql.Internal;
using Microsoft.EntityFrameworkCore.SqlServer.Query.Internal;
using Microsoft.EntityFrameworkCore.Query.SqlExpressions;
namespace Microsoft.EntityFrameworkCore
{
public static class CustomDbContextOptionsBuilderExtensions
{
public static DbContextOptionsBuilder UseCustomSqlServerQuerySqlGenerator(this DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.ReplaceService<IQuerySqlGeneratorFactory, CustomSqlServerQuerySqlGeneratorFactory>();
return optionsBuilder;
}
}
}
namespace Microsoft.EntityFrameworkCore.SqlServer.Query.Sql.Internal
{
class CustomSqlServerQuerySqlGeneratorFactory : IQuerySqlGeneratorFactory
{
public CustomSqlServerQuerySqlGeneratorFactory(QuerySqlGeneratorDependencies dependencies)
=> Dependencies = dependencies;
public QuerySqlGeneratorDependencies Dependencies { get; }
public QuerySqlGenerator Create() => new CustomSqlServerQuerySqlGenerator(Dependencies);
}
public class CustomSqlServerQuerySqlGenerator : SqlServerQuerySqlGenerator
{
public CustomSqlServerQuerySqlGenerator(QuerySqlGeneratorDependencies dependencies)
: base(dependencies) { }
protected override Expression VisitTable(TableExpression tableExpression)
{
// base will append schema, table and alias
var result = base.VisitTable(tableExpression);
Sql.Append(" WITH (NOLOCK)");
return result;
}
}
}
EF 核心 2.x:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using Microsoft.EntityFrameworkCore.Query.Expressions;
using Microsoft.EntityFrameworkCore.Query.Sql;
using Microsoft.EntityFrameworkCore.Storage;
using Microsoft.EntityFrameworkCore.SqlServer.Infrastructure.Internal;
using Microsoft.EntityFrameworkCore.SqlServer.Query.Sql.Internal;
namespace Microsoft.EntityFrameworkCore
{
public static class CustomDbContextOptionsBuilderExtensions
{
public static DbContextOptionsBuilder UseCustomSqlServerQuerySqlGenerator(this DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.ReplaceService<IQuerySqlGeneratorFactory, CustomSqlServerQuerySqlGeneratorFactory>();
return optionsBuilder;
}
}
}
namespace Microsoft.EntityFrameworkCore.SqlServer.Query.Sql.Internal
{
class CustomSqlServerQuerySqlGeneratorFactory : SqlServerQuerySqlGeneratorFactory
{
private readonly ISqlServerOptions sqlServerOptions;
public CustomSqlServerQuerySqlGeneratorFactory(QuerySqlGeneratorDependencies dependencies, ISqlServerOptions sqlServerOptions)
: base(dependencies, sqlServerOptions) => this.sqlServerOptions = sqlServerOptions;
public override IQuerySqlGenerator CreateDefault(SelectExpression selectExpression) =>
new CustomSqlServerQuerySqlGenerator(Dependencies, selectExpression, sqlServerOptions.RowNumberPagingEnabled);
}
public class CustomSqlServerQuerySqlGenerator : SqlServerQuerySqlGenerator
{
public CustomSqlServerQuerySqlGenerator(QuerySqlGeneratorDependencies dependencies, SelectExpression selectExpression, bool rowNumberPagingEnabled)
: base(dependencies, selectExpression, rowNumberPagingEnabled) { }
public override Expression VisitTable(TableExpression tableExpression)
{
// base will append schema, table and alias
var result = base.VisitTable(tableExpression);
Sql.Append(" WITH (NOLOCK)");
return result;
}
}
}
相当多的代码仅用于添加一个有意义的行，但这样做的好处是，如果存在此类查询选项，它的执行方式可能与 EF Core 的执行方式相同。
无论如何，使用上面的代码，您只需要从您的上下文OnConfiguring override 中激活它:
optionsBuilder.UseCustomSqlServerQuerySqlGenerator();
关于c# - Ef-Core - 我可以使用什么正则表达式在 Db 拦截器中用 nolock 替换表名，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/53078435/