MongoDB聚合运算符：$setIntersection

文章目录

MongoDB聚合运算符：$setIntersection
- 语法
- 使用
- 举例
- - 元素数组举例
  - 检索授予当前用户角色的文档
  - - 创建角色
    - 创建用户
    - 创建集合
    - 使用John登录
    - 检索文档
    - 检查文档
    - 使用Jane登录
    - 检索文档
    - 验证文档

$setIntersection聚合运算符返回两个或多个数组的交集。

语法

{ $setIntersection: [ <array1>, <array2>, ... ] }

字段说明：

参数可以是任何有效的数组表达式。

使用

$setIntersection 对数组执行集合操作，将数组视为集合，如果数组包含重复元素，$setIntersection会忽略重复元素，$setIntersection忽略元素的顺序。
$setIntersection 过滤掉结果中的重复项，输出仅包含唯一元素的数组，输出数组中元素的顺序未指定。
如果未找到交集（即输入数组不包含公共元素），则 $setIntersection 返回一个空数组。
如果集合包含嵌套数组元素，则 $setIntersection 不会下降到嵌套数组，而处理顶层数组。

例如	结果
`{ $setIntersection: [ [ "a", "b", "a" ], [ "b", "a" ] ] }`	`[ "b", "a" ]`
`{ $setIntersection: [ [ "a", "b" ], [ [ "a", "b" ] ] ] }`	`[]`

举例

元素数组举例

使用下面的脚本创建flowers集合：

db.flowers.insertMany( [{ "_id" : 1, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "rose", "orchid" ] },{ "_id" : 2, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "orchid", "rose", "orchid" ] },{ "_id" : 3, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "rose", "orchid", "jasmine" ] },{ "_id" : 4, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "jasmine", "rose" ] },{ "_id" : 5, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ ] },{ "_id" : 6, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ [ "rose" ], [ "orchid" ] ] },{ "_id" : 7, "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ [ "rose", "orchid" ] ] },{ "_id" : 8, "flowerFieldA" : [ ], "flowerFieldB" : [ ] },{ "_id" : 9, "flowerFieldA" : [ ], "flowerFieldB" : [ "rose" ] }
] )

以下操作使用 $setIntersection 运算符返回flowerFieldA 数组和flowerFieldB 数组共有的元素数组：：

db.flowers.aggregate([{ $project: { flowerFieldA: 1, flowerFieldB: 1, commonToBoth: { $setIntersection: [ "$flowerFieldA", "$flowerFieldB" ] }, _id: 0 } }]
)

操作返回下面的结果：

{ "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "rose", "orchid" ], "commonToBoth" : [ "orchid", "rose" ] }
{ "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "orchid", "rose", "orchid" ], "commonToBoth" : [ "orchid", "rose" ] }
{ "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "rose", "orchid", "jasmine" ], "commonToBoth" : [ "orchid", "rose" ] }
{ "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ "jasmine", "rose" ], "commonToBoth" : [ "rose" ] }
{ "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ ], "commonToBoth" : [ ] }
{ "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ [ "rose" ], [ "orchid" ] ], "commonToBoth" : [ ] }
{ "flowerFieldA" : [ "rose", "orchid" ], "flowerFieldB" : [ [ "rose", "orchid" ] ], "commonToBoth" : [ ] }
{ "flowerFieldA" : [ ], "flowerFieldB" : [ ], "commonToBoth" : [ ] }
{ "flowerFieldA" : [ ], "flowerFieldB" : [ "rose" ], "commonToBoth" : [ ] }

检索授予当前用户角色的文档

从 MongoDB 7.0 开始，可以使用新的 USER_ROLES 系统变量来返回用户角色。

下面的例子展示了不同角色的用户对budget集合中的文档具有不同的访问权限。展示了 USER_ROLES 在进行权限检索时的一种用途，budget集合包含的文档中有一个名为 allowedRoles 的字段，在下面的场景中将会看到，可以编写查询，将 allowedRoles 字段中的用户角色与 USER_ROLES 系统变量返回的角色进行比较。

执行以下步骤创建角色、用户和budget集合：

创建角色

db.createRole( { role: "Marketing", roles: [], privileges: [] } )
db.createRole( { role: "Sales", roles: [], privileges: [] } )
db.createRole( { role: "Development", roles: [], privileges: [] } )
db.createRole( { role: "Operations", roles: [], privileges: [] } )

创建用户

创建名为 John 和 Jane 的用户，并设置所需的角色。

db.createUser( {user: "John",pwd: "jn008",roles: [{ role: "Marketing", db: "test" },{ role: "Development", db: "test" },{ role: "Operations", db: "test" },{ role: "read", db: "test" }]
} )db.createUser( {user: "Jane",pwd: "je009",roles: [{ role: "Sales", db: "test" },{ role: "Operations", db: "test" },{ role: "read", db: "test" }]
} )

创建集合

db.budget.insertMany( [{_id: 0,allowedRoles: [ "Marketing" ],comment: "For marketing team",yearlyBudget: 15000},{_id: 1,allowedRoles: [ "Sales" ],comment: "For sales team",yearlyBudget: 17000,salesEventsBudget: 1000},{_id: 2,allowedRoles: [ "Operations" ],comment: "For operations team",yearlyBudget: 19000,cloudBudget: 12000},{_id: 3,allowedRoles: [ "Development" ],comment: "For development team",yearlyBudget: 27000}
] )

执行以下步骤来检索 John 可以访问的文档：

使用John登录

db.auth( "John", "jn008" )

检索文档

使用系统变量，将 $$ 添加到变量名称的开头。将 USER_ROLES 系统变量指定为 $$USER_ROLES。

db.budget.aggregate( [ {$match: {$expr: {$not: {$eq: [ { $setIntersection: [ "$allowedRoles", "$$USER_ROLES.role" ] }, [] ]}}}
} ] )

上例从budget集合中返回与运行该示例的用户角色匹配的文档，使用 $setIntersection 返回budget文档 allowedRoles 字段与 $$USER_ROLES 中的用户角色集之间的交集不为空的文档。

检查文档

John 担任营销、运营和开发角色：

[{_id: 0,allowedRoles: [ 'Marketing' ],comment: 'For marketing team',yearlyBudget: 15000},{_id: 2,allowedRoles: [ 'Operations' ],comment: 'For operations team',yearlyBudget: 19000,cloudBudget: 12000},{_id: 3,allowedRoles: [ 'Development' ],comment: 'For development team',yearlyBudget: 27000}
]

执行以下步骤来检索 Jane 可访问的文档：

使用Jane登录

db.auth( "Jane", "je009" )

检索文档

要使用系统变量，可将 $$ 添加到变量名称的开头。将 USER_ROLES 系统变量指定为 $$USER_ROLES。

db.budget.aggregate( [ {$match: {$expr: {$not: {$eq: [ { $setIntersection: [ "$allowedRoles", "$$USER_ROLES.role" ] }, [] ]}}}
} ] )

验证文档

Jane 具有销售和运营角色：

[{_id: 1,allowedRoles: [ 'Sales' ],comment: 'For sales team',yearlyBudget: 17000,salesEventsBudget: 1000},{_id: 2,allowedRoles: [ 'Operations' ],comment: 'For operations team',yearlyBudget: 19000,cloudBudget: 12000}
]