How to implement inner join in mongoose - mongodb

Question

Problem:
I want to achieve an inner join in mongoose for a model which has dynamic ref and direct ref to another model(s). Pls refer to the sample schema and models below.
const schema1 = mongoose.schema({
on: {
type: Schema.Types.ObjectId,
required: true,
refPath: 'onModel'
},
onModel: {
type: String,
required: true,
enum: ['Model2', 'Model3']
},
company: {
type: Schema.Types.ObjectId,
ref: 'Company'
}
});
const Model1 = mongoose.model('Model1', schema1);
const schema2 = mongoose.schema({
name: {
type: String,
maxlength: 100
},
email: {
type: String,
maxlength: 100
}
});
const Model2 = mongoose.model('Model2', schema2);
const schema3 = mongoose.schema({
name: {
type: String,
maxlength: 100
},
email: {
type: String,
maxlength: 100
}
});
const Model3 = mongoose.model('Model3', schema3);
const companySchema = mongoose.schema({
companyName: {
type: String,
maxlength: 100
}
});
const company = mongoose.model('Company', companySchema);
const res = await models.Model1
.find()
.populate({
path: 'on',
match: {
'name': keyword
}
})
.populate({
path: 'company',
match: {
'companyName': keyword
}
});
The above find returns documents even if on and company returns null value (as mongoose populate implements left join by default).
Expected Result: I want to fetch documents from model1 only if it matches the keyword with name field in model2 or model3 or with company name field in company model.
How to achieve this? Your help is much appreciated.

Answer 1

1.Let's update the schema for "Model 1" like below:-
const schema1=mongoose.schema( {
ref: {
kind: String, // <-- This will store the Model Name (Model2 or Model3) when you execute the insert query.
item: {
type: mongoose.Schema.Types.ObjectId, // <-- This will store the Reference ID of another table (Model2 OR Model3)
refPath: 'ref.kind', fields: String,
}
,
}
, company: {
type: Schema.Types.ObjectId, ref: 'Company'
}
});
Keep the schema for Model2 , Model3 & Company as it is. No need to make any change here.
When you want to find :-
await models.Model1.find().populate({ path: 'ref.item' });
That's it. This should work.