Which should I choose, Document Model or Relation Model? - database

Question

In my application, I choose Document Model but I still have some questions.
Here is my example document:
{
"catalogs": {
"cat-id1": {
"name": "catalog-1",
"createdAt": 123,
"products": {
"pro-id1": {
"name": "product-1",
"createdAt": 321,
"ingredients": {}
},
"pro-id2": {
"name": "product-2",
"createdAt": 654,
"ingredients": {}
}
}
},
"cat-id2": {
"name": "catalog-2",
"createdAt": 456,
"products": {
"pro-id3": {
"name": "product-3",
"createdAt": 322,
"ingredients": {}
},
"pro-id4": {
"name": "product-4",
"createdAt": 655,
"ingredients": {}
}
}
}
}
}
But ingredients in product is referrer to another Document.
{
"ingredients": {
"ing-id1": {},
"ing-id2": {}
}
}
Document Model has several benefits:
Easy to edit schema, like if (user.first_name) user.first_name = user.name.split(' ')[0]
No need to join, easily take all data in once.
Also I know that:
On updates to a document, the entire document usually needs to be rewritten.
For these reasons, it is generally recommended that you keep documents fairly small and avoid writes that increase the size of a document .
Main idea is: Which data model leads to simpler application code?
My question will be:
What size of Document should I keep?
My application already have a Relation DB, should I combined Document Model to Relation DB to reducing complexity?

Answer 1

Since you already have a relational database in use, I don't see a real benefit to using a document based DB as well.
Your Database schema seems simple enough to be using a relational DB. Wheras, if catalog entries would be very different from each other, you might consider a document based model. But this does not seem to be the case.
Therefore, my advice is, you stick with a relational model.
I would design the model like this:
A table for each entity (catalog, product, ingredient) where each entry has a unique Id
A relation table for each n:m relationship (catalogProduct, productIngredient) that only contain the Id of the entities of the relationship.
An example:
The ingredients ing1, ing2 and ing3 are stored in the table ingredient.
The products prod1 and prod2 are stored in product.
ing1 and ing2 are needed for prod1
ing2 and ing3 for prod2
In productIngredient in each entry, you store the ID of an ingredient and the ID of the product it is used in.
prod1 : ing1
prod1 : ing2
prod2 : ing2
prod2 : ing3