I have two collections. One to store all the user Details and another to store movies. I have a user_id field which has the objectId of the user who uploads it in the movie collection. Now I need to store all the movie ObjectId's as a array in the corresponding user collection. Like one to many relationship. say, I have some movie documents :
[{
'id' : '1',
'title' : 'Pk',
'user_id' : '25'
},
{
'id' : '2',
'title' : 'Master',
'user_id' : '25'
}]
In user collection, I want to store all the Movie_id's as a array to the corresponding user.
{
'user_id' : '25',
'user_name' : 'john',
'Movie_ids' : ['1','2']
}
How can I achieve this using mongodb and express.js?
Query
$lookup does what you want (see mongodb documentation is very good)$map is used to keep only the ids in the arraydb.users.aggregate([
{
"$lookup": {
"from": "movies",
"localField": "user_id",
"foreignField": "user_id",
"as": "movies"
}
},
{
"$set": {
"movies": {
"$map": {
"input": "$movies",
"in": "$$this.id"
}
}
}
}
])
Ok, I'm not sure if this is entirely what you are looking for but you can use javascript function .filter on the movie object to get all the movies with user_id=25 and then map the id's of those movies to a new array like this:
let movies = [
{
"id": "1",
"name": "pk",
"user_id": "25"
},{
"id": "2",
"name": "Master",
"user_id": "25"
}]
let user = {
"id": "25",
"name": "john"
}
let sortedMovies = movies.filter(movie => movie.user_id === user.id).map(movie => movie.id);
user.movieIDs = sortedMovies;
A link to test the code: https://playcode.io/816962/