let’s consider i have some collection and the structures of data is look like these
post col:
{
_id: ObjectId("5fce0e137ff7401634bad2ac")
address: "new york"
description: "this is a great city"
image: "images\0.4644859674390589-gikiguk.jpg"
userId: "5fcdcd8487e37216bc82171b"
}
user col:
{
_id: ObjectId("5fcdcd8487e37216bc82171b")
name: "jack"
profile: {image: "images\0.4644859674390589-dofowfg.jpg", description: "be happy dude"}
email: "test@test.com"
password: "2a$12$gzRrY83QAjwLhdyvn3JQ2OcMj3XG65.BULva4cZqcuSxDhhMbSXCq"
}
likesComments col:
{
_id: ObjectId("5fce0e191ff7301666kao2xc")
likes: {quantity: 1, likes: [{isActive: true, userId: "5fcdcd8487c31216cc87886r"}]}
comments: {quantity: 1, comments: [{userId: "5fcdcd8487c31216cc87886r" , comment: "awesome city"}]}
postId: "5fce0e137ff7401634bad2ac"
}
what i want to do is i have a userId (maybe more than one) that i want to search through all of posts (that is belong to the user) and get some data from posts collection and then $lookup to users collection that again get some data about user and after that every post has own postId (i converted _id to postId ). with postId i can $lookup to likeComments documents and get some data about any posts, but if a post don’t have any likes or comments, all of my query that i wrote them gives me an empty array [] (not data at all just empty array) but if a post has at least one like and one comment, all of my query works find.
what i expect is something like this:
[
{
postId: '5fce0e137ff7401634bad2ac', //from post
location: 'shiraz', // from post
description: 'this is a greate city', // from post
image: 'images\\0.4644859674390589-gikiguk.jpg', // from post
userId: '5fcdcd8487e37216bc82171b', // from user
name: 'mohammad', // from user
profile: 'images\\0.6093033055735912-DSC_0002_2.JPG', // from user
comments: { quantity: 1, comments: [{userId: "...", name: "...", profile: "...", comment: "..."}] }, // from likesComments and then lookup to users documets to get data about users that wrote comments
likes: {quantity: 1, [{userId: "...", name: "...", profile: "..."}]} // from likesCommnets and then lookup to users documets to get data about users that liked the post
}
]
query:
i know that my query is wrong but i can’t find what’s wrong here.
db.collection("posts")
.aggregate([
{ $match: { userId: { $in: users.map(u => u) } } },
{
$project: {
_id: 0,
userId: { $toObjectId: "$userId" },
postId: { $toString: "$_id" },
location: "$address",
description: "$description",
image: "$image"
}
},
{
$lookup: {
from: "users",
localField: "userId",
foreignField: "_id",
as: "userInfo"
}
},
{ $unwind: "$userInfo" },
{
$project: {
_id: 0,
postId: 1,
location: 1,
description: 1,
image: 1,
userId: { $toString: "$userId" },
name: "$userInfo.name",
profile: "$userInfo.profile.image"
}
},
{
$lookup: {
from: "likes-comments",
localField: "postId",
foreignField: "postId",
as: "likesComments"
}
},
{ $unwind: "$likesComments" },
{
$project: {
postId: 1,
location: 1,
description: 1,
image: 1,
userId: 1,
name: 1,
profile: 1,
likes: {
$map: {
input: "$likesComments.likes.likes",
as: "item",
in: {
$toObjectId: "$item.userId"
}
}
},
quantity: "$likesComments.comments.quantity",
comments: {
comments: {
$map: {
input: "$likesComments.comments.comments",
as: "item",
in: {
$toObjectId: "$item.userId"
}
}
}
}
}
},
{
$lookup: {
from: "users",
localField: "likes",
foreignField: "_id",
as: "likes"
}
},
{ $unwind: "$likes" },
{
$lookup: {
from: "users",
localField: "comments.comments",
foreignField: "_id",
as: "comments"
}
},
{ $unwind: "$comments" },
{ $addFields: { quantity: "$quantity" } },
{
$project: {
_id: 0,
postId: 1,
location: 1,
description: 1,
image: 1,
userId: 1,
name: 1,
profile: 1,
likes: [
{
userId: { $toString: "$likes._id" },
name: "$likes.name",
profile: "$likes.profile.image"
}
],
comments: {
quantity: 1,
comments: [
{
userId: { $toString: "$comments._id" },