它is documented并且已知 EF 核心迁移脚本不支持删除列。所以我试着用手做。
我的模型类是:
class Master
{
public int Id { get; set; }
public string ToBeDeleted { get; set; }
}
class Detail
{
public int Id { get; set; }
public Master Master { get; set; }
}
我的背景:
class Context : DbContext
{
public DbSet<Master> Masters { get; set; }
public DbSet<Detail> Details { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseSqlite("Filename=local.db");
base.OnConfiguring(optionsBuilder);
}
}
我创建了一个迁移脚本,然后运行以下程序来创建数据库文件并添加几行:
class Program
{
static void Main(string[] args)
{
using (var context = new Context())
{
context.Database.Migrate();
if(!context.Masters.Any())
{
var master = new Master {ToBeDeleted = "Some string"};
context.Add(master);
context.Add(new Detail {Master = master});
context.SaveChanges();
}
}
}
}
我删除了 Master
类的 ToBeDeleted
属性并生成了第二个迁移脚本,该脚本生成了非常简单的代码,但该代码不起作用,因为它仅在未来:
protected override void Up(MigrationBuilder migrationBuilder)
{
migrationBuilder.DropColumn(
name: "ToBeDeleted",
table: "Masters");
}
protected override void Down(MigrationBuilder migrationBuilder)
{
migrationBuilder.AddColumn<string>(
name: "ToBeDeleted",
table: "Masters",
nullable: true);
}
所以是时候写我自己的东西了,这是我尝试过的:
protected override void Up(MigrationBuilder migrationBuilder)
{
migrationBuilder.Sql("PRAGMA foreign_keys=OFF");
migrationBuilder.CreateTable(
name: "NEW_Masters",
columns: table => new
{
Id = table.Column<int>(nullable: false)
.Annotation("Sqlite:Autoincrement", true),
},
constraints: table =>
{
table.PrimaryKey("PK_Masters", x => x.Id);
});
migrationBuilder.Sql("INSERT INTO NEW_Masters SELECT Id FROM Masters;");
migrationBuilder.DropTable("Masters");
migrationBuilder.RenameTable("NEW_Masters", newName: "Masters");
migrationBuilder.Sql("PRAGMA foreign_keys=OFF");
}
然而,这会导致 context.Database.Migrate()
抛出异常:
An unhandled exception of type 'Microsoft.Data.Sqlite.SqliteException' occurred in Microsoft.EntityFrameworkCore.Relational.dll
Additional information: SQLite Error 19: 'FOREIGN KEY constraint failed'.
最后,问题:如何在迁移脚本中手动删除列?
更新
根据我在讨论中得到的建议,我使用 Script-Migration
从迁移脚本生成 sql 并得到了这个:
CREATE TABLE IF NOT EXISTS "__EFMigrationsHistory" (
"MigrationId" TEXT NOT NULL CONSTRAINT "PK___EFMigrationsHistory" PRIMARY KEY,
"ProductVersion" TEXT NOT NULL
);
CREATE TABLE "Masters" (
"Id" INTEGER NOT NULL CONSTRAINT "PK_Masters" PRIMARY KEY AUTOINCREMENT,
"ToBeDeleted" TEXT
);
CREATE TABLE "Details" (
"Id" INTEGER NOT NULL CONSTRAINT "PK_Details" PRIMARY KEY AUTOINCREMENT,
"MasterId" INTEGER,
CONSTRAINT "FK_Details_Masters_MasterId" FOREIGN KEY ("MasterId") REFERENCES "Masters" ("Id") ON DELETE RESTRICT
);
CREATE INDEX "IX_Details_MasterId" ON "Details" ("MasterId");
INSERT INTO "__EFMigrationsHistory" ("MigrationId", "ProductVersion")
VALUES ('20170127204056_Migration1', '1.1.0-rtm-22752');
INSERT INTO Masters (ToBeDeleted) VALUES ("ASDF"); --I've added this line manually for test only
INSERT INTO Details (MasterId) VALUES (1); --I've added this line manually for test only
PRAGMA foreign_keys="0";
CREATE TABLE "NEW_Masters" (
"Id" INTEGER NOT NULL CONSTRAINT "PK_Masters" PRIMARY KEY AUTOINCREMENT
);
INSERT INTO NEW_Masters SELECT Id FROM Masters;;
DROP TABLE "Masters";
ALTER TABLE "NEW_Masters" RENAME TO "Masters";
PRAGMA foreign_keys="1";
INSERT INTO "__EFMigrationsHistory" ("MigrationId", "ProductVersion")
VALUES ('20170127204851_Migration2', '1.1.0-rtm-22752');
脚本运行良好。异常(exception)是 EF 在某处执行的一些外键检查。
最佳答案
EF core developers指出 PRAGMA foreign_keys=0
在 SQLite 的事务中不起作用,建议使用 migrationBuilder.Sql
方法来抑制事务的使用。
所以我想出了:
protected override void Up(MigrationBuilder migrationBuilder)
{
migrationBuilder.CreateTable(
name: "NEW_Masters",
columns: table => new
{
Id = table.Column<int>(nullable: false)
.Annotation("Sqlite:Autoincrement", true),
},
constraints: table =>
{
table.PrimaryKey("PK_Masters", x => x.Id);
});
migrationBuilder.Sql("INSERT INTO NEW_Masters SELECT Id FROM Masters;");
migrationBuilder.Sql("PRAGMA foreign_keys=\"0\"", true);
migrationBuilder.Sql("DROP TABLE Masters", true);
migrationBuilder.Sql("ALTER TABLE NEW_Masters RENAME TO Masters", true);
migrationBuilder.Sql("PRAGMA foreign_keys=\"1\"", true);
}
它确实起到了作用。
关于sql - EF Core - 删除列解决方法(sqlite),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/41902905/