[英]Using aggregate $lookup and $mergeObjects
我想加入收藏。 之前,我只使用查找,这样我就可以得到连接的分隔字段。 但我需要得到类似mysql join的结果。 我注意到这个动作有$ lookup和$ mergeObjects,但效果不好。
用户集合模型。
{
"_id": ObjectId("xxxxxxx"), //this is default id from mongoDB
"name": 'admin user',
"email": 'admin@test.com',
"password": 'xxxxxxxx',
"roles": [
{
"id": 0,
"approved": true
},{
"id": 2,
"approved": true
}
]
},{
"_id": ObjectId("xxxxxxx"), //this is default id from mongoDB
"name": 'userOne',
"email": 'user@test.com',
"password": 'xxxxxxxx',
"roles": [
{
"id": 1,
"approved": true
}
]
}
角色集合模型。
{
"_id": ObjectId("xxxxxxx"), //this is default id from mongoDB
"id": '0',
"name": 'administrator'
},{
"_id": ObjectId("xxxxxxx"), //this is default id from mongoDB
"id": '0',
"name": 'employeer'
},{
"_id": ObjectId("xxxxxxx"), //this is default id from mongoDB
"id": '0',
"name": 'freelancer'
}
加入后,我希望获得如下结果。
{
"_id": ObjectId("xxxxxxx"), //this is default id from mongoDB
"name": 'admin user',
"email": 'admin@test.com',
"password": 'xxxxxxxx',
"roles": [
{
"id": 0,
"name": "administrator", //join result
"approved": true
},{
"id": 2,
"name": "freelancer", //join result
"approved": true
}
]
},{
"_id": ObjectId("xxxxxxx"), //this is default id from mongoDB
"name": 'userOne',
"email": 'user@test.com',
"password": 'xxxxxxxx',
"roles": [
{
"id": 1,
"name": "employeer", //join result
"approved": true
}
]
}
您可以使用以下aggregation
与mongodb 3.4
您需要首先$unwind
roles数组,然后再$group
再次回滚
db.users.aggregate([
{ "$unwind": "$roles" },
{ "$lookup": {
"from": "roles",
"localField": "roles.id",
"foreignField": "id",
"as": "roles.role"
}},
{ "$unwind": "$roles.role" },
{ "$addFields": {
"roles": { "$mergeObjects": ["$roles.role", "$roles"] }
}},
{ "$group": {
"_id": "$_id",
"email": { "$first": "$email" },
"password": { "$first": "$password" },
"roles": { "$push": "$roles" }
}},
{ "$project": { "roles.role": 0 }}
])
使用mongodb 3.6及以上版本非常简单
db.users.aggregate([
{ "$unwind": "$roles" },
{ "$lookup": {
"from": "roles",
"let": { "roleId": "$roles.id", "approved": "$roles.approved" },
"pipeline": [
{ "$match": { "$expr": { "$eq": ["$id", "$$roleId"] }}},
{ "$addFields": { "approved": "$$approved" }}
],
"as": "roles"
}},
{ "$unwind": "$roles" },
{ "$group": {
"_id": "$_id",
"email": { "$first": "$email" },
"password": { "$first": "$password" },
"roles": { "$push": "$roles" }
}}
])
两者都会给你类似的输出
[
{
"_id": ObjectId("5a934e000102030405000004"),
"email": "user@test.com",
"password": "xxxxxxxx",
"roles": [
{
"_id": ObjectId("5a934e000102030405000001"),
"approved": true,
"id": 1,
"name": "employeer"
}
]
},
{
"_id": ObjectId("5a934e000102030405000003"),
"email": "admin@test.com",
"password": "xxxxxxxx",
"roles": [
{
"_id": ObjectId("5a934e000102030405000000"),
"approved": true,
"id": 0,
"name": "administrator"
},
{
"_id": ObjectId("5a934e000102030405000002"),
"approved": true,
"id": 2,
"name": "freelancer"
}
]
}
]
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