I am building an apllication with mongoose and node.js that enables you to post, comment, and like both the posts and the comments.
I am tryign to build a query that gets all the information from the db.
saw that answer nested 3 level lookup like in here MongoDB nested lookup with 3 levels. it works, but the project filter returns me an error and if I remove it, I get some comments that looks like that:
"comments":
{
"user": [],
"likes": []
}
the argigate
postArgigate = [
{
//lookup for the post likes
$lookup: {
from: 'likes',
localField: '_id',
foreignField: 'postCommentID',
as: '_likes'
},
},
//the user wrote the post
{
$lookup: {
from: 'users',
localField: 'userID',
foreignField: '_id',
as: 'user'
},
},
{
$lookup: {
from: 'comments',
localField : 'commentsID',
foreignField : '_id',
as: 'comments'
},
},
//unwind the comments to do a nesting lookup
{
$unwind: {
path: "$comments",
preserveNullAndEmptyArrays: true
}
},
//lookup in the comments likes
{
$lookup: {
from: 'likes',
localField : 'comments._id',
foreignField : 'postCommentID',
as: 'comments._likes'
},
},
//lookup in the user that wrote the comment
{
$lookup: {
from: 'users',
localField: 'comments.userID',
foreignField: '_id',
as: 'comments.user'
},
},
{
$set: {
'comments.likes':'$comments._likes.userID',
'likes': '$_likes.userID'
}
},
{
$project: {
/////////FILTER NOT WORKING////////////
// 'comments': {
// $filter: { input: "$comments", as: "cm", cond: { $ifNull: ["$$cm._id", false] } }
// } , //returns an error
'comments.userID':0,
'comments.user.password':0,
'comments._likes':0,
'userID':0,
'user.password':0,
'commentsID':0,
'_likes': 0,
}
},
{
$group: {
_id : "$_id",
user:{$first:'$user'},
likes:{$first:'$likes'},
date:{$first:'$date'},
content:{$first:'$content'},
comments: { $push: "$comments" },
}
}
]
thank you for you help!
comments
[
{
_id: ObjectId("com1"),
userID:ObjectId("eliran1"),
content: 'comment 1',
date: 2022-03-02T22:55:16.224Z,
},
{
_id:ObjectId("com2"),
userID: ObjectId("eliran1"),
content: 'comment 2',
date: 2022-03-05T18:34:52.890Z,
__v: 0
}
]
posts
[
{
_id: new ObjectId("post1"),
userID: new ObjectId("eliran1"),
content: 'post 1',
commentsID: [],
date: 2022-03-05T18:28:11.487Z,
},
{
_id: new ObjectId("post2"),
userID: new ObjectId("shira1"),
content: 'post 2',
commentsID: [ObjectId("com1"),
ObjectId("com2") ],
date: 2022-03-05T18:34:46.364Z,
}
]
users
[
{
_id: new ObjectId("eliran1"),
user: 'eliran222',
password: '123456789',
email: 'fdfd@fdfd.com33',
gender: true,
__v: 0
},
{
_id: new ObjectId("shira1"),
user: 'shira3432',
password: '123456789',
email: 'fdrf@gfge.com',
gender: false,
}
]
likes
[
{
_id: ObjectId("like1"),
userID: ObjectId("eliran1"),
postCommentID:ObjectId("post1"),
},
{
_id:ObjectId("like2"),
userID: ObjectId("shira1"),
postCommentID:ObjectId("com1"),
}
]
expected results:
[
{
_id: new ObjectId("post1"),
user: {
user: 'eliran222',
email: 'fdfd@fdfd.com33',
gender: true,
},
content: 'post 1',
comments: [],
date: 2022-03-05T18:28:11.487Z,
likes:[{/*eliran`s user*/}]
},
{
_id: new ObjectId("post2"),
userID: {
_id: new ObjectId("shira1"),
user: 'shira3432',
email: 'fdrf@gfge.com',
gender: false,
},
content: 'post 2',
comments: [{
_id: ObjectId("com1"),
user:{
_id:objectId(eliran1)
user: 'eliran222',
email: 'fdfd@fdfd.com33',
gender: true,
},
content: 'comment 1',
date: 2022-03-02T22:55:16.224Z,
likes:[{/*shira`s user*/}]
},
{
_id:ObjectId("com2"),
user: {
objectId(eliran1)
user: 'eliran222',
email: 'fdfd@fdfd.com33',
gender: true,
},
content: 'comment 2',
date: 2022-03-05T18:34:52.890Z,
likes:[]
}],
date: 2022-03-05T18:34:46.364Z,
}
]
}
]
