升级MongoDB Client至v6.8.0后Typegoose鉴别器与索引异常

问题描述 #

将MongoDB Client从v4.7.x升级到v6.8.0后，使用Typegoose定义的鉴别器模型，其继承自父类的唯一索引被自动添加了partialFilterExpression，导致(make, color)的唯一性约束仅对单个鉴别器（如mazda或cadi）生效，而非全局生效。

原模型定义：

@index({ make: 1, color: 1 }, { unique: true, background: false })
@modelOptions({
    options: { allowMixed: Severity.ALLOW },
    schemaOptions: { collection: 'cars', discriminatorKey: 'make' },
})
class Car extends defaultClasses.TimeStamps {
    @prop({ required: true })
    make: string;

    @prop({ required: true })
    color: string;
}

const CarModel = getModelForClass(Car);

class Mazda extends Car {}
const MazdaModel = getDiscriminatorModelForClass(CarModel, Mazda, 'mazda');

class Cadillac extends Car {}
const CadillacModel = getDiscriminatorModelForClass(CarModel, Cadillac, 'cadi');

升级后调用listIndex()返回的索引带有partialFilterExpression，示例：

[{"v":2,"unique":true,"key":{"make":1,"color":1},"name":"make_1_color_1","background":false,"partialFilterExpression":{"make":"mazda"}}]

原因 #

MongoDB Node.js驱动v6.x或Typegoose的更新中，鉴别器模型继承父类索引时，会自动为索引添加partialFilterExpression，将索引范围限制到当前鉴别器的discriminatorKey值——默认行为是避免不同鉴别器之间的索引冲突，但不符合全局唯一约束的需求。

解决方法 #

方法1：手动创建全局唯一索引（推荐） #

跳过鉴别器自动继承索引的逻辑，直接在父模型上手动创建全局索引：

@modelOptions({
    options: { allowMixed: Severity.ALLOW },
    schemaOptions: { collection: 'cars', discriminatorKey: 'make' },
})
class Car extends defaultClasses.TimeStamps {
    @prop({ required: true })
    make: string;

    @prop({ required: true })
    color: string;
}

const CarModel = getModelForClass(Car);

// 手动添加全局唯一索引
await CarModel.createIndex({ make: 1, color: 1 }, { unique: true, background: false });

// 创建鉴别器
class Mazda extends Car {}
const MazdaModel = getDiscriminatorModelForClass(CarModel, Mazda, 'mazda');

class Cadillac extends Car {}
const CadillacModel = getDiscriminatorModelForClass(CarModel, Cadillac, 'cadi');

方法2：禁用鉴别器的索引继承 #

如果坚持使用装饰器定义父类索引，可在创建鉴别器时禁用索引继承：

@index({ make: 1, color: 1 }, { unique: true, background: false })
@modelOptions({
    options: { allowMixed: Severity.ALLOW },
    schemaOptions: { collection: 'cars', discriminatorKey: 'make' },
})
class Car extends defaultClasses.TimeStamps {
    @prop({ required: true })
    make: string;

    @prop({ required: true })
    color: string;
}

const CarModel = getModelForClass(Car);

// 创建鉴别器时禁用索引继承
class Mazda extends Car {}
const MazdaModel = getDiscriminatorModelForClass(CarModel, Mazda, 'mazda', {
    discriminatorOptions: { inheritIndexes: false }
});

class Cadillac extends Car {}
const CadillacModel = getDiscriminatorModelForClass(CarModel, Cadillac, 'cadi', {
    discriminatorOptions: { inheritIndexes: false }
});

验证 #

执行await CarModel.listIndexes()，返回的索引应无partialFilterExpression：

[{"v":2,"unique":true,"key":{"make":1,"color":1},"name":"make_1_color_1","background":false}]

此时插入不同make但相同color的文档会触发唯一约束错误，符合全局唯一的需求。

内容的提问来源于stack exchange，提问作者Felix Koblenz