如何避免在MongoDB中更改字段数据类型？

Question

I'm new to MongoDB and I'm starting a new project with Spring Data MongoDB.

I created a simple model POJO and I inserted some documents into products collection:

@Document(collection="products")
public class Product {
    @Id
    private String id;
    private String name;
    private double price;
    private int quantity;

    // ...
}

In my DB field types are mapped correctly:

• name to String ,
• price to Double ,
• quantity to Int32

But making some test i tried to increment quantity field via $inc modifier:

db.products.update({"name" : "A product"}, {"$inc" : {"quantity" : 1}});

and now quantity field type is changed to Double .

How can I avoid this?

Answer 1

Thanks to Neil Lunn comment, I realized that a way to keep the same data type for my quantity field is to explicitly specify the type of the increment amount.

In this case I have an Int32 so I can use this code to update it:

db.products.update({"name" : "A product"}, {"$inc" : {"quantity" : NumberInt(1)}});