树形实体

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TypeORM 支持使用邻接列表和闭包表模式存储树形结构。要深入了解分层数据表，请查看 Bill Karwin 的精彩演示。

邻接列表

邻接列表是通过自引用来实现的简单模型。请注意 TreeRepository 不支持邻接列表模式。这种方法的优势在于简单易用，缺点是受连接操作限制，无法一次性加载大型树结构。要了解邻接列表的更多优势和使用场景，请参阅 Matthew Schinckel 的文章。示例：

import {
    Entity,
    Column,
    PrimaryGeneratedColumn,
    ManyToOne,
    OneToMany,
} from "typeorm"

@Entity()
export class Category {
    @PrimaryGeneratedColumn()
    id: number

    @Column()
    name: string

    @Column()
    description: string

    @ManyToOne((type) => Category, (category) => category.children)
    parent: Category

    @OneToMany((type) => Category, (category) => category.parent)
    children: Category[]
}

嵌套集

嵌套集是另一种存储树形结构的数据库模式。该模式读取效率极高，但写入性能较差。嵌套集不支持多个根节点。示例：

import {
    Entity,
    Tree,
    Column,
    PrimaryGeneratedColumn,
    TreeChildren,
    TreeParent,
    TreeLevelColumn,
} from "typeorm"

@Entity()
@Tree("nested-set")
export class Category {
    @PrimaryGeneratedColumn()
    id: number

    @Column()
    name: string

    @TreeChildren()
    children: Category[]

    @TreeParent()
    parent: Category
}

物化路径（路径枚举）

物化路径（也称为路径枚举）是另一种存储树形结构的数据库模式。该方法简单且高效。示例：

import {
    Entity,
    Tree,
    Column,
    PrimaryGeneratedColumn,
    TreeChildren,
    TreeParent,
    TreeLevelColumn,
} from "typeorm"

@Entity()
@Tree("materialized-path")
export class Category {
    @PrimaryGeneratedColumn()
    id: number

    @Column()
    name: string

    @TreeChildren()
    children: Category[]

    @TreeParent()
    parent: Category
}

闭包表

闭包表通过特殊方式在独立表中存储父子关系。该模式在读取和写入操作中都具有高效性。示例：

import {
    Entity,
    Tree,
    Column,
    PrimaryGeneratedColumn,
    TreeChildren,
    TreeParent,
    TreeLevelColumn,
} from "typeorm"

@Entity()
@Tree("closure-table")
export class Category {
    @PrimaryGeneratedColumn()
    id: number

    @Column()
    name: string

    @TreeChildren()
    children: Category[]

    @TreeParent()
    parent: Category
}

您可以通过在 @Tree("closure-table", options) 中设置可选参数 options 来指定闭包表名称和/或列名。ancestorColumnName 和 descandantColumnName 是回调函数，它们接收主列的元数据并返回列名称。

@Tree("closure-table", {
    closureTableName: "category_closure",
    ancestorColumnName: (column) => "ancestor_" + column.propertyName,
    descendantColumnName: (column) => "descendant_" + column.propertyName,
})

操作树形实体

要将树形实体相互关联，需要在子实体中设置父实体然后保存：

const a1 = new Category()
a1.name = "a1"
await dataSource.manager.save(a1)

const a11 = new Category()
a11.name = "a11"
a11.parent = a1
await dataSource.manager.save(a11)

const a12 = new Category()
a12.name = "a12"
a12.parent = a1
await dataSource.manager.save(a12)

const a111 = new Category()
a111.name = "a111"
a111.parent = a11
await dataSource.manager.save(a111)

const a112 = new Category()
a112.name = "a112"
a112.parent = a11
await dataSource.manager.save(a112)

使用 TreeRepository 加载树形结构：

const trees = await dataSource.manager.getTreeRepository(Category).findTrees()

trees 结果将如下所示：

[
    {
        "id": 1,
        "name": "a1",
        "children": [
            {
                "id": 2,
                "name": "a11",
                "children": [
                    {
                        "id": 4,
                        "name": "a111"
                    },
                    {
                        "id": 5,
                        "name": "a112"
                    }
                ]
            },
            {
                "id": 3,
                "name": "a12"
            }
        ]
    }
]

通过 TreeRepository 操作树形实体还有以下专用方法：

findTrees - 返回数据库中所有树形结构及其全部子节点、孙节点等。

const treeCategories = await dataSource.manager
    .getTreeRepository(Category)
    .findTrees()
// returns root categories with sub categories inside

const treeCategoriesWithLimitedDepth = await dataSource.manager
    .getTreeRepository(Category)
    .findTrees({ depth: 2 })
// returns root categories with sub categories inside, up to depth 2

findRoots - 根节点指没有祖先的实体。该方法查找所有根节点，但不会加载其叶子节点。

const rootCategories = await dataSource.manager
    .getTreeRepository(Category)
    .findRoots()
// returns root categories without sub categories inside

findDescendants - 获取指定实体的所有后代子节点，以扁平数组形式返回。

const children = await dataSource.manager
    .getTreeRepository(Category)
    .findDescendants(parentCategory)
// returns all direct subcategories (without its nested categories) of a parentCategory

findDescendantsTree - 获取指定实体的所有后代子节点，以嵌套树形结构返回。

const childrenTree = await repository.findDescendantsTree(parentCategory)
// returns all direct subcategories (with its nested categories) of a parentCategory
const childrenTreeWithLimitedDepth = await repository.findDescendantsTree(
    parentCategory,
    { depth: 2 },
)
// returns all direct subcategories (with its nested categories) of a parentCategory, up to depth 2

createDescendantsQueryBuilder - 创建用于获取树形结构中实体后代的查询构建器。

const children = await repository
    .createDescendantsQueryBuilder(
        "category",
        "categoryClosure",
        parentCategory,
    )
    .andWhere("category.type = 'secondary'")
    .getMany()

countDescendants - 获取指定实体的后代数量。

const childrenCount = await dataSource.manager
    .getTreeRepository(Category)
    .countDescendants(parentCategory)

findAncestors - 获取指定实体的所有祖先节点，以扁平数组形式返回。

const parents = await repository.findAncestors(childCategory)
// returns all direct childCategory's parent categories (without "parent of parents")

findAncestorsTree - 获取指定实体的所有祖先节点，以嵌套树形结构返回。

const parentsTree = await dataSource.manager
    .getTreeRepository(Category)
    .findAncestorsTree(childCategory)
// returns all direct childCategory's parent categories (with "parent of parents")

createAncestorsQueryBuilder - 创建用于获取树形结构中实体祖先的查询构建器。

const parents = await repository
    .createAncestorsQueryBuilder("category", "categoryClosure", childCategory)
    .andWhere("category.type = 'secondary'")
    .getMany()

countAncestors - 获取指定实体的祖先数量。

const parentsCount = await dataSource.manager
    .getTreeRepository(Category)
    .countAncestors(childCategory)

以下方法可接收配置选项：

findTrees
findRoots
findDescendants
findDescendantsTree
findAncestors
findAncestorsTree

可用配置选项如下：

relations - 指定应加载的实体关联关系（简化左连接形式）。

示例：

const treeCategoriesWithRelations = await dataSource.manager
    .getTreeRepository(Category)
    .findTrees({
        relations: ["sites"],
    })
// automatically joins the sites relation

const parentsWithRelations = await dataSource.manager
    .getTreeRepository(Category)
    .findAncestors(childCategory, {
        relations: ["members"],
    })
// returns all direct childCategory's parent categories (without "parent of parents") and joins the 'members' relation

邻接列表​

嵌套集​

物化路径（路径枚举）​

闭包表​

操作树形实体​

邻接列表

嵌套集

物化路径（路径枚举）

闭包表

操作树形实体