我有一个汇总查询,可从3个集合中获取结果。
我正在使用mongoDb 3.4
结果中有一个样本文档。
{
"_id" : ObjectId("5ba1717ee4b00ce08ca47cfa"),
"name" : "captain jack",
"email" : "[email protected]",
"mobile" : "9000000023",
"status" : "verified",
"courses" : [
{
"_id" : "13",
"name" : "Course (03)"
},{
"_id" : "12",
"name" : "Course (03)"
}
],
"examCompleted" : false,
"login" : "5ba1717ee4b00fe08ca47cfa",
"partnerMetaInfo" : {
"_id" : ObjectId("5ba1717ee4b00fe08ca47cfa"),
"costCode" : "5761",
"hub" : "CALCUTTA",
"location" : "Kolkata"
}
}
我试图将
partnerMetaInfo
引入根目录。我也无法使用_id == 13上的$ match来过滤courses._id
这是我的汇总查询:
db.getCollection("mainCollection").aggregate([
{
//Join two collection
$lookup:{
from: "Details",
localField: "username",
foreignField: "login",
as: "partnerData"
}
},{
//Limit fields
$project:{
"email":1,
"name":1,
"mobile":1,
"status" : 1,
"courses":"$partnerData.courses",
"examScore" : "$partnerData.examScore",
"examCompleted" : "$partnerData.examCompleted",
"login":"$partnerData.login"
}
},
{
//Join third collection
$lookup:{
from: "PartnerMetaInfo",
localField: "login",
foreignField: "partnerId",
as: "partnerMetaInfo"
}
},
//Remove from partnerData array and place at root level.
{
$unwind:
{
path: '$courses',
preserveNullAndEmptyArrays: true
}
},{
$unwind:
{
path: '$examScore',
preserveNullAndEmptyArrays: true
}
},{
$unwind:
{
path: '$examCompleted',
preserveNullAndEmptyArrays: true
}
},{
$unwind:
{
path: '$login',
preserveNullAndEmptyArrays: true
}
},//Bring $partnerMetaInfo array to root level.
{
$unwind:
{
path: '$partnerMetaInfo',
preserveNullAndEmptyArrays: true
}
},{
$limit:10
}
];
$ unwind之后的partnerMetaInfo最终成为对象。我想将其展平,并将其置于根目录下。
有人可以帮助我吗?
最佳答案
如果您想要得到的只是partnerMetaInfo
字段的内容,则可以在管道的末尾添加一个$replaceRoot阶段,如下所示:
{
$replaceRoot: { "newRoot": { $ifNull: [ "$partnerMetaInfo", {} ] } }
}
否则,如果您只想将
partnerMetaInfo
字段内的字段移动到根目录,则可以使用$addFields:{
$addFields: {
"partnerMetaInfoId" : "$partnerMetaInfo._id",
"costCode" : "$partnerMetaInfo.costCode",
"hub" : "$partnerMetaInfo.hub",
"location" : "$partnerMetaInfo.location"
}
}
如果您具有动态数量的字段,或者不想对字段名称进行硬编码,则可以使用以下逻辑:
{
$replaceRoot: { // merge fields of and move them all the way up
"newRoot": { $mergeObjects: [ "$$ROOT", "$partnerMetaInfo" ] }
}
}, {
$project: { // remove the "partnerMetaInfo" field
"partnerMetaInfo": 0
}
}
关于node.js - 在mongoDb中将对象放置到根级别,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/53040711/