Mongoose query to filter the collection based on nested field - node.js

Question

We want to see if mongoose could do heavy lifting to get the user's role for a given Organization Name and UserId.
This can be done easily by first finding out the organization data and use javascript to filter out based on User's ID. But i think it would give better performance if the query can do it instead of doing outside the mongo collection.
What we want to try something like below, but it is not giving the role of the user correctly.
Query (not working)
public async getUserOrgRole(orgName: string, userId) {
const result = await this.organizationModel
.findOne({ name: orgName, 'orgMembers.userId': userId })
.select('orgMembers.role')
.exec();
if (result) {
const orgMember = _.get(result, 'orgMembers');
return orgMember[0].role;
}
return null;
}
Query (working but we want the above query to work instead of pulling entire document)
public async getUserOrgRole(orgName: string, userId) {
const org = await this.organizationModel.findOne({ name: orgName })
if (!org)
return null;
const userInOrg = org.orgMembers.find(om => om.userId === userId)
console.log('--getUserOrgRole', userInOrg)
if (userInOrg)
return userInOrg.role
return null;
}
Schema
const UserOrgSchema = new Schema({
role: { type: Schema.Types.String, enum: ['MEMBER', 'OWNER', 'ADMIN'], default: 'MEMBER' },
inactive: { type: Schema.Types.Boolean, default: false },
userId: { type: Schema.Types.String, required: true },
});
const OrganizationSchema = new Schema({
name: { type: Schema.Types.String, unique: true },
picture: { type: Schema.Types.String },
orgMembers: { type: [UserOrgSchema] },
createdAt: { type: Schema.Types.Date, default: Date.now },
updatedAt: { type: Schema.Types.Date, default: Date.now },
});

Answer 1

You almost got it right. The reason why your attempt does not quite work is explained by Sunil. No matter what filters you apply to .find(), it will always return the whole document. If you want to select specific subdocuments, you need to do that using an additional select operator. This ought to work:
const result = await this.organizationModel
.findOne({ name: orgName, "orgMembers.userId": userId })
.select({
orgMembers: {
$elemMatch: {
userId,
},
},
})
.select("orgMembers.role")
.exec();
Note the use of $elemMatch! It does exactly what you wanted - filters the subdocuments by selecting only the ones that match the provided filter.