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前言

隨著系統(tǒng)的不斷開發(fā)和迭代默認的efcore功能十分強大，但是隨著Saas系統(tǒng)的引進efcore基于表字段的多租戶模式已經(jīng)非常完美了，但是基于數(shù)據(jù)庫的多租戶也是可以用的，但是也存在缺點，缺點就是沒有辦法支持不同數(shù)據(jù)庫，migration support multi database provider with single dbcontext，本人不才，查詢了一下，官方文檔只說明了dbcontext的遷移如何實現(xiàn)多數(shù)據(jù)源，但是缺不是單個dbcontext,這個就讓人很頭疼。所以秉著嘗試一下的原則進行了這篇博客的編寫,因為本人只有mmsql和mysql所以這次就用這兩個數(shù)據(jù)庫來做測試

廣告時間

本人開發(fā)了一款efcore的分表分庫讀寫分離組件

https://github.com/dotnetcore/sharding-core

希望有喜歡的小伙伴給我點點star謝謝

那么廢話不多說我們馬上開始migration support multi database provider with single dbcontext

新建項目

1.按裝依賴

2.新建一個User類

[Table(nameof(User))]
public class User{
    public string UserId { get; set; }
    public string UserName { get; set; }
}

3.創(chuàng)建DbContext

public class MyDbContext:DbContext
{
    public DbSet<User> Users { get; set; }
    public MyDbContext(DbContextOptions<MyDbContext> options):base(options)
    {
        
    }

4.StartUp配置

var provider = builder.Configuration.GetValue("Provider", "UnKnown");//Add-Migration InitialCreate -Context MyDbContext -OutputDir Migrations\SqlServer -Args "--provider SqlServer"//Add-Migration InitialCreate -Context MyDbContext -OutputDir Migrations\MySql -Args "--provider MySql"builder.Services.AddDbContext<MyDbContext>(options =>
{
    _ = provider switch
    {        "MySql" => options.UseMySql("server=127.0.0.1;port=3306;database=DBMultiDataBase;userid=root;password=L6yBtV6qNENrwBy7;", new MySqlServerVersion(new Version())),        "SqlServer" => options.UseSqlServer("Data Source=localhost;Initial Catalog=DBMultiDataBase;Integrated Security=True;"),
        _ => throw new Exception($"Unsupported provider: {provider}")
    };
});

遷移區(qū)分數(shù)據(jù)庫

新建一個遷移命名空間提供者


    public interface IMigrationNamespace
    {        string GetNamespace();
    }

mysql和sqlserver的實現(xiàn)分別是項目名稱遷移文件夾

    public class MySqlMigrationNamespace:IMigrationNamespace
    {
        public string GetNamespace()
        {            return "EFCoreMigrateMultiDatabase.Migrations.MySql";
        }
    }

    public class SqlServerMigrationNamespace:IMigrationNamespace
    {
        public string GetNamespace()
        {            return "EFCoreMigrateMultiDatabase.Migrations.SqlServer";
        }
    }

efcore擴展

添加efcore擴展

    public class MigrationNamespaceExtension : IDbContextOptionsExtension
    {
        public IMigrationNamespace MigrationNamespace { get; }

        public MigrationNamespaceExtension(IMigrationNamespace migrationNamespace)
        {
            MigrationNamespace = migrationNamespace;
        }
        public void ApplyServices(IServiceCollection services)
        {
            services.AddSingleton<IMigrationNamespace>(sp => MigrationNamespace);
        }

        public void Validate(IDbContextOptions options)
        {
        }


        public DbContextOptionsExtensionInfo Info => new MigrationNamespaceExtensionInfo(this);

        private class MigrationNamespaceExtensionInfo : DbContextOptionsExtensionInfo
        {
            private readonly MigrationNamespaceExtension _migrationNamespaceExtension;
            public MigrationNamespaceExtensionInfo(IDbContextOptionsExtension extension) : base(extension)
            {
                _migrationNamespaceExtension = (MigrationNamespaceExtension)extension;
            }

            public override int GetServiceProviderHashCode() => _migrationNamespaceExtension.MigrationNamespace.GetNamespace().GetHashCode();

            public override bool ShouldUseSameServiceProvider(DbContextOptionsExtensionInfo other) => true;

            public override void PopulateDebugInfo(IDictionary<string, string> debugInfo)
            {
            }

            public override bool IsDatabaseProvider => false;
            public override string LogFragment => "MigrationNamespaceExtension";
        }
    }

重寫MigrationsAssembly支持多數(shù)據(jù)庫

    public class EFCoreMultiDatabaseMigrationsAssembly: IMigrationsAssembly
    {
        public  string MigrationNamespace { get; }
        private readonly IMigrationsIdGenerator _idGenerator;
        private readonly IDiagnosticsLogger<DbLoggerCategory.Migrations> _logger;
        private IReadOnlyDictionary<string, TypeInfo>? _migrations;
        private ModelSnapshot? _modelSnapshot;
        private readonly Type _contextType;        /// <summary>
        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
        ///     any release. You should only use it directly in your code with extreme caution and knowing that
        ///     doing so can result in application failures when updating to a new Entity Framework Core release.
        /// </summary>
        public EFCoreMultiDatabaseMigrationsAssembly(
            IMigrationNamespace migrationNamespace,
            ICurrentDbContext currentContext,
            IDbContextOptions options,
            IMigrationsIdGenerator idGenerator,
            IDiagnosticsLogger<DbLoggerCategory.Migrations> logger)
        {

            _contextType = currentContext.Context.GetType();

            var assemblyName = RelationalOptionsExtension.Extract(options)?.MigrationsAssembly;
            Assembly = assemblyName == null
                ? _contextType.Assembly
                : Assembly.Load(new AssemblyName(assemblyName));

            MigrationNamespace = migrationNamespace.GetNamespace();
            _idGenerator = idGenerator;
            _logger = logger;
        }        /// <summary>
        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
        ///     any release. You should only use it directly in your code with extreme caution and knowing that
        ///     doing so can result in application failures when updating to a new Entity Framework Core release.
        /// </summary>
        public virtual IReadOnlyDictionary<string, TypeInfo> Migrations
        {
            get
            {
                IReadOnlyDictionary<string, TypeInfo> Create()
                {
                    var result = new SortedList<string, TypeInfo>();
                    var items
                        = from t in Assembly.GetConstructibleTypes()
                          where t.IsSubclassOf(typeof(Migration))&& print(t)
                                && t.Namespace.Equals(MigrationNamespace)
                              && t.GetCustomAttribute<DbContextAttribute>()?.ContextType == _contextType
                          let id = t.GetCustomAttribute<MigrationAttribute>()?.Id
                          orderby id
                          select (id, t);
                    Console.WriteLine("Migrations:" + items.Count());
                    foreach (var (id, t) in items)
                    {                        if (id == null)
                        {
                            _logger.MigrationAttributeMissingWarning(t);                            continue;
                        }

                        result.Add(id, t);
                    }                    return result;
                }                return _migrations ??= Create();
            }
        }

        private bool print(TypeInfo t)
        {
            Console.WriteLine(MigrationNamespace);
            Console.WriteLine(t.Namespace);            return true;
        }        /// <summary>
        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
        ///     any release. You should only use it directly in your code with extreme caution and knowing that
        ///     doing so can result in application failures when updating to a new Entity Framework Core release.
        /// </summary>
        public virtual ModelSnapshot? ModelSnapshot
            => GetMod();

        private ModelSnapshot GetMod()
        {
            Console.WriteLine("_modelSnapshot:"+ _modelSnapshot);            if (_modelSnapshot == null)
            {
                Console.WriteLine("_modelSnapshot:null");
                _modelSnapshot = (from t in Assembly.GetConstructibleTypes()
                        where t.IsSubclassOf(typeof(ModelSnapshot)) && print(t)
                                                                    && MigrationNamespace.Equals(t?.Namespace)
                                                                    && t.GetCustomAttribute<DbContextAttribute>()?.ContextType == _contextType
                        select (ModelSnapshot)Activator.CreateInstance(t.AsType())!)
                    .FirstOrDefault();

                Console.WriteLine("_modelSnapshot:" + _modelSnapshot);
            }            return _modelSnapshot;
        }        /// <summary>
        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
        ///     any release. You should only use it directly in your code with extreme caution and knowing that
        ///     doing so can result in application failures when updating to a new Entity Framework Core release.
        /// </summary>
        public virtual Assembly Assembly { get; }        /// <summary>
        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
        ///     any release. You should only use it directly in your code with extreme caution and knowing that
        ///     doing so can result in application failures when updating to a new Entity Framework Core release.
        /// </summary>
        public virtual string? FindMigrationId(string nameOrId)
            => Migrations.Keys
                .Where(
                    _idGenerator.IsValidId(nameOrId)                        // ReSharper disable once ImplicitlyCapturedClosure
                        ? id => string.Equals(id, nameOrId, StringComparison.OrdinalIgnoreCase)
                        : id => string.Equals(_idGenerator.GetName(id), nameOrId, StringComparison.OrdinalIgnoreCase))
                .FirstOrDefault();        /// <summary>
        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
        ///     any release. You should only use it directly in your code with extreme caution and knowing that
        ///     doing so can result in application failures when updating to a new Entity Framework Core release.
        /// </summary>
        public virtual Migration CreateMigration(TypeInfo migrationClass, string activeProvider)
        {
            Console.WriteLine(migrationClass.FullName);

            var migration = (Migration)Activator.CreateInstance(migrationClass.AsType())!;
            migration.ActiveProvider = activeProvider;            return migration;
        }
    }折疊

編寫startup

參考 https://docs.microsoft.com/en-us/ef/core/managing-schemas/migrations/providers?tabs=vs

//Add-Migration InitialCreate -Context MyDbContext -OutputDir Migrations\SqlServer -Args "--provider SqlServer"//Add-Migration InitialCreate -Context MyDbContext -OutputDir Migrations\MySql -Args "--provider MySql"//update-database -Args "--provider MySql"//update-database -Args "--provider SqlServer"builder.Services.AddDbContext<MyDbContext>(options =>
{
    options.ReplaceService<IMigrationsAssembly, EFCoreMultiDatabaseMigrationsAssembly>();
    _ = provider switch
    {        "MySql" => options.UseMySql("server=127.0.0.1;port=3306;database=DBMultiDataBase;userid=root;password=L6yBtV6qNENrwBy7;", new MySqlServerVersion(new Version()))
            .UseMigrationNamespace(new MySqlMigrationNamespace()),        "SqlServer" => options.UseSqlServer("Data Source=localhost;Initial Catalog=DBMultiDataBase;Integrated Security=True;")
        .UseMigrationNamespace(new SqlServerMigrationNamespace()),
        _ => throw new Exception($"Unsupported provider: {provider}")
    };
});

到此為止我這邊想我們應(yīng)該已經(jīng)實現(xiàn)了把,但是如果我們分別執(zhí)行兩個遷移命令會導(dǎo)致前一個遷移命令被覆蓋掉,經(jīng)過一整個下午的debug調(diào)試最后發(fā)現(xiàn)是因為在遷移腳本生成寫入文件的時候會判斷當(dāng)前DbContext'的ModelSnapshot,同一個dbcontext生成的文件是一樣的，所以我們這邊有兩個選擇

1.讓生成的文件名不一樣
2.讓ModelSnapshot不進行深度查詢只在當(dāng)前目錄下處理
這邊選了第二種

    public class MyMigrationsScaffolder: MigrationsScaffolder
    {
        private readonly Type _contextType;
        public MyMigrationsScaffolder(MigrationsScaffolderDependencies dependencies) : base(dependencies)
        {
            _contextType = dependencies.CurrentContext.Context.GetType();
        }
        protected override string GetDirectory(string projectDir, string? siblingFileName, string subnamespace)
        {
            var defaultDirectory = Path.Combine(projectDir, Path.Combine(subnamespace.Split('.')));            if (siblingFileName != null)
            {                if (!siblingFileName.StartsWith(_contextType.Name + "ModelSnapshot."))
                {
                    var siblingPath = TryGetProjectFile(projectDir, siblingFileName);                    if (siblingPath != null)
                    {
                        var lastDirectory = Path.GetDirectoryName(siblingPath)!;                        if (!defaultDirectory.Equals(lastDirectory, StringComparison.OrdinalIgnoreCase))
                        {
                            Dependencies.OperationReporter.WriteVerbose(DesignStrings.ReusingNamespace(siblingFileName));                            return lastDirectory;
                        }
                    }
                }
            }            return defaultDirectory;
        }
    }

添加designservices

    public class MyMigrationDesignTimeServices: IDesignTimeServices
    {
        public void ConfigureDesignTimeServices(IServiceCollection serviceCollection)
        {
            serviceCollection.AddSingleton<IMigrationsScaffolder, MyMigrationsScaffolder>();
        }
    }

遷移

分別運行兩個遷移命令

運行更新數(shù)據(jù)庫命令

記得我們需要在參數(shù)里面添加選項

下期預(yù)告

下期我們將實現(xiàn)efcore在Saas系統(tǒng)下的多租戶+code-first(遷移)+分表+分庫+讀寫分離+動態(tài)分表+動態(tài)分庫+動態(tài)讀寫分離+動態(tài)添加多租戶全程零sql腳本的解決方案

是不是buffer疊滿

最后的最后

附上demo:EFCoreMigrateMultiDatabase https://github.com/xuejmnet/EFCoreMigrateMultiDatabase

您都看到這邊了確定不點個star或者贊嗎,一款.Net不得不學(xué)的分庫分表解決方案,簡單理解為sharding-jdbc在.net中的實現(xiàn)并且支持更多特性和更優(yōu)秀的數(shù)據(jù)聚合,擁有原生性能的97%,并且無業(yè)務(wù)侵入性,支持未分片的所有efcore原生查詢

github地址 https://github.com/xuejmnet/sharding-core
gitee地址 https://gitee.com/dotnetchina/sharding-core

EFCore高級Saas系統(tǒng)下單DbContext如何支持不同數(shù)據(jù)庫的遷移

前言