从 mongodb 中的三个集合中获取结果

Question

我有三个集合包含像波纹管这样的数据，

客户集合

{ 
"_id" : ObjectId("5a058e316803fafd127b23c9"), 
"client_name" : "client A", 
"client_status" : "A"
}
{ 
"_id" : ObjectId("5a058e316803fafd127b23cb"), 
"client_name" : "client B", 
"client_status" : "A"
}

池集合

{ 
"_id" : ObjectId("5a0e76f66803fa530a7b23d4"), 
"pool_name" : "pool A", 
"pool_status" : "A", 
"client_id" : ObjectId("5a058e316803fafd127b23c9"), 
"schools" : [
ObjectId("5a0e742b6803faa6097b2462"), 
ObjectId("5a0e742b6803faa6097b2464")
]
}
{ 
"_id" : ObjectId("5a0e76f76803fa530a7b2402"), 
"pool_name" : "pool B", 
"pool_status" : "A", 
"client_id" : ObjectId("5a058e316803fafd127b23c9"), 
"schools" : [
ObjectId("5a0e742b6803faa6097b2463")
]
}
{ 
"_id" : ObjectId("5a0e76f76803fa530a7b23f6"), 
"pool_name" : "pool C", 
"pool_status" : "A", 
"client_id" : ObjectId("5a058e316803fafd127b23cb"), 
"schools" : [
ObjectId("5a7aa1476803fa1f117b23d1")
]
}

学校收藏

{ 
"_id" : ObjectId("5a0e742b6803faa6097b2462"), 
"school_name" : "School A", 
"school_status" : "A"
}
{ 
"_id" : ObjectId("5a0e742b6803faa6097b2463"), 
"school_name" : "School B", 
"school_status" : "A"
}
{ 
"_id" : ObjectId("5a0e742b6803faa6097b2464"), 
"school_name" : "School C", 
"school_status" : "A"
}
{ 
"_id" : ObjectId("5a7aa1476803fa1f117b23d1"), 
"school_name" : "School D", 
"school_status" : "A"
}

从这个集合中，我需要为像波纹管这样的客户获取池学校列表。

**Output**
{
"_id" : ObjectId("5a058e316803fafd127b23c9"),
"client_name" : "client A", 
"client_status" : "A"
"pools" : [
{
"_id" : ObjectId("5a0e76f66803fa530a7b23d4"), 
"pool_name" : "pool A", 
"pool_status" : "A",
'schools' => [
{ 
"_id" : ObjectId("5a0e742b6803faa6097b2462"), 
"school_name" : "School A", 
"school_status" : "A"
},
{ 
"_id" : ObjectId("5a0e742b6803faa6097b2464"), 
"school_name" : "School C", 
"school_status" : "A"
},
]
},
{
"_id" : ObjectId("5a0e76f76803fa530a7b2402"), 
"pool_name" : "pool B", 
"pool_status" : "A",
"schools" : [
{ 
"_id" : ObjectId("5a0e742b6803faa6097b2463"), 
"school_name" : "School B", 
"school_status" : "A"
}   
]
}
]
},
{
"_id" : ObjectId("5a058e316803fafd127b23cb"), 
"client_name" : "client B",
"client_status" : "A"
"pools" : [
{
"_id" : ObjectId("5a0e76f76803fa530a7b23f6"), 
"pool_name" : "pool C", 
"pool_status" : "A",
"schools" : [
{ 
"_id" : ObjectId("5a7aa1476803fa1f117b23d1"), 
"school_name" : "School D", 
"school_status" : "A"
}
]
}
]
}

Answer 1

你可以试试下面的聚合

Mongodb 3.6引入了嵌套$lookup管道...因此，您不需要像上面那样使用另一个$lookup阶段......可以在此处使用嵌套$lookup管道

Client.aggregate([
{ "$match": { 'client_status': 'A' } },
{ "$lookup": {
"from": Pool.collection.name,
"let": { "client_id": "$_id" },
"pipeline": [
{ "$match": { "$expr": { "$eq": [ "$client_id", "$$client_id" ] } } },
{ "$addFields": {
"schools": {
"$ifNull": ["$schools", []]
}
}}
{ "$lookup": {
"from": Schools.collection.name,
"let": { "schools": "$schools" },
"pipeline": [
{ "$match": { "$expr": { "$in": [ "$_id", "$$schools" ] } } }
],
"as": "schools"
}}
],
"as": "pools"
}}
])

对于冗长的解释，您可以不$unwind地通过$lookup多个级别吗？