Mongoose - can't insert subDocuments of a Dictionary Type - mongodb

Question

I have a Mongoose schema for the document Company, that has several fields. One of these (documents_banks) is a "free" field, of dictionary type, because I don't know the names of the keys in advance.
The problem is that, when I save the document (company.save()) even if the resulting saved document has the new sub_docs, in the DB no new sub_docs are actually saved.
var Company = new Schema({
banks: [{ type: String }], // array of Strings
documents_banks: {} // free field
});
Even if documents_banks is not restricted by the Schema, it will have this structure (in my mind):
{
"bank_id1": {
"doc_type1": {
"url": { "type": "String" },
"custom_name": { "type": "String" }
},
"doc_type2": {
"url": { "type": "String" },
"custom_name": { "type": "String" }
}
},
"bank_id2": {
"doc_type1": {
"url": { "type": "String" },
"custom_name": { "type": "String" }
}
}
}
But I don't know in advance names of keys bank_id neither doc_type, so I used the Dictionary type (documents_banks:{}).
Now, this below is the function I use to save new sub_docs in documents_banks. The same logic I always use to save new sub_docs.. Anyway this time, it seems saved, but it's not.
function addBankDocument(company_id, bank_id, doc_type, url, custom_name) {
// retrieve the company document
Company.findById(company_id)
.then(function(company) {
// create empty sub_docs if needed
if (!company.documents_banks) {
company.documents_banks = {};
}
if (!company.documents_banks[bank_id]) {
company.documents_banks[bank_id] = {};
}
// add the new sub_doc
company.documents_bank[bank_id][doc_type] = {
"url": url,
"custom_name": custom_name
};
return company.save();
})
.then(function(saved_company) {
// I try to check if the new obj has been saved
console.log(saved_company.documents_bank[bank_id][doc_type]);
// and it actually prints the new obj!!
});
}
The saved_company returned by the .save() actually has the new sub_docs, but if I check the DB there is not the new sub_doc! I can save just the first one, all the others are not stored.
So, the console.log() always print the new sub_docs, but actually in the DataBase, just the first sub_doc is saved, not the others. So at the end, saved_company always has 1 sub_doc, the first one.
It seems very strange to me, since saved_company has the new sub_docs. What can be happened?
This below is a real extract from by DB, and it will contains forever just the sub_doc "doc_bank#1573807781414", others will be not present in the DB.
{
"_id": "5c6eaf8efdc21500146e289c", // company_id
"banks": [ "MPS" ],
"documents_banks": {
"5c5ac3e025acd98596021a9a": // bank_id
{
"doc_bank#1573807781414": // doc_type
{
"url": "http://...",
"custom_name": "file1"
}
}
}
}
Versions:
$ npm -v
6.4.1
$ npm show mongoose version
5.7.11
$ node -v
v8.16.0

Answer 1

It seems that, since mongoose doesn't know the exact model of the subdoc, it can't know when it changes. So I have to use markModified to notify changes of the "free field" (also known as dictionary or MixedType) with this:
company_doc.documents_banks["bank_id2"]["doc_type3"] = obj; // modify
company_doc.markModified('documents_banks'); // <--- notify changes
company_doc.save(); // save changes
As I understood, markModified force the model to 'update' that field during the save().