我必须有两个集合，一个是游览，另一个是目的地，因此在游览中我有一个位置数组，该数组具有带有id的目标对象，并且该id属于另一个Destinations集合，但问题是我无法查找详细信息位置数组中的目标位置。每个人也尝试过许多查询搜索。但没有得到预期的结果。
游览：
{
"_id" : ObjectId("5f3122f4d8d57e3b9650e5b4"),
"title" : "tour 1",
"locations" : [
{
"destination" : {
"id" : "5ec5ae9037ea99f20a79071a"
},
"services" : {
"hotel" : true
}
},
{
"destination" : {
"id" : "5ec5ae8e37ea99f20a78ef8c"
},
"services" : {
"hotel" : true
}
}
]
}
{
"_id" : ObjectId("5f2d65e68bc6e9155310d147"),
"title" : "tour 2",
"locations" : [
{
"destination" : {
"id" : "5ecf994435c3a6025d5bf126"
},
"services" : {
"hotel" : true
}
}
]
}
{
"_id" : ObjectId("5f2d66398bc6e9155310d161"),
"title" : "tour 3",
"locations" : [
{
"destination" : {
"id" : "5ec5ae8e37ea99f20a78ef8d"
},
"services" : {
"hotel" : true
}
}
]
}
目的地：
{
"_id" : ObjectId("5ec5ae9037ea99f20a79071a"),
"name" : "dest 1",
"country" : "country name"
}
{
"_id" : ObjectId("5ec5ae8e37ea99f20a78ef8c"),
"name" : "dest 2",
"country" : "country name"
}
{
"_id" : ObjectId("5ec5ae8e37ea99f20a78ef8d"),
"name" : "dest 3",
"country" : "country name"
}
{
"_id" : ObjectId("5ecf994435c3a6025d5bf126"),
"name" : "dest 4",
"country" : "country name"
}
预期结果 ：
{
"_id" : ObjectId("5f3122f4d8d57e3b9650e5b4"),
"title" : "tour 1",
"locations" : [
{
"destination" : {
"id" : "5ec5ae9037ea99f20a79071a",
"name" : "dest 1",
"country" : "country name"
},
"services" : {
"hotel" : true
}
},
{
"destination" : {
"id" : "5ec5ae8e37ea99f20a78ef8c",
"name" : "dest 2",
"country" : "country name"
},
"services" : {
"hotel" : true
}
}
]
},
{
"_id" : ObjectId("5f2d65e68bc6e9155310d147"),
"title" : "tour 2",
"locations" : [
{
"destination" : {
"id" : "5ecf994435c3a6025d5bf126",
"name" : "dest 4",
"country" : "country name"
},
"services" : {
"hotel" : true
}
}
]
},
{
"_id" : ObjectId("5f2d66398bc6e9155310d161"),
"title" : "tour 3",
"locations" : [
{
"destination" : {
"id" : "5ec5ae8e37ea99f20a78ef8d",
"name" : "dest 3",
"country" : "country name"
},
"services" : {
"hotel" : true
}
}
]
}
尝试查询：
db.tours.aggregate([
{
"$addFields": {
"locations": {
"$map": {
"input": "$locations",
"in": {
"$mergeObjects": [
"$$this",
{
"dest_oid": {
"$toObjectId": "$$this.destination.id"
}
}
]
}
}
}
}
},
{ "$unwind": "$locations" },
{ "$lookup": {
"from": "destinations",
"localField": "locations.dest_oid",
"foreignField": "_id",
"as": "locations.dest",
}},
{ "$unwind": "$locations.dest" },
{ "$group": {
"_id": "$_id",
"locations": { "$push": "$locations" }
}}
])
甚至我已经在嵌套文档上尝试过这个MongoDB $ lookup
快速修复
$unwind locations 数组放在第一位，因为需要将id转换为对象iddb.tours.aggregate([
{ $unwind: "$locations" },
$addFields替换locations.destination.id为对象ID可以简化您的逻辑，这里不需要$ map和$ mergeObjects选项 {
$addFields: {
"locations.destination.id": {
$toObjectId: "$locations.destination.id"
}
}
},
$lookup 您已经做过，但更改为 locations.destination {
$lookup: {
from: "destinations",
as: "locations.destination",
localField: "locations.destination.id",
foreignField: "_id"
}
},
locations.destination因为它的数组而我们需要对象 {
$unwind: {
path: "$locations.destination"
}
},
$group 您已经做过的事情，进行了一些更改，将第一个目的地和服务推送到位置，并添加了第一个标题 {
$group: {
_id: "$_id",
locations: { $push: "$locations" },
title: { $first: "$title" }
}
}
])
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