MongoDB _ id attribute description

Generally, the ID field of a relational database is a self-increasing numeric type, but the _ id field of MongoDB is very strange. It can be unique, but it is not a simple type, not a number, it is not a string. I almost thought it was a string when I first came into contact.

In fact, it is a special object. In the JS shell of MongoDB, you can see that it is an object type and has a series of methods and attributes. The tostring attribute can return a string.

It is worth noting that after we get the _ ID of the object type, the. tostring cannot be used for search, cannot be converted, and can only be searched by the object type ....

For more information, see the following documents:
Http://www.mongodb.org/display/DOCS/Object+IDs
Http://api.mongodb.org/python/current/api/bson/objectid.html#module-bson.objectid