Implement automatically increase ids in MongoDB

In MongoDB, every documents have an object id (Bson ID). But sometimes we need ids that can automatically increase when creating a new model. And the id should be an integer starts from 1. How to deal with the problem?

How to solve the problem

To solve the problem, we have to create a new collection named AutoIncrementIdCollection, in which we insert some models (AutoIncrementIdModel) that have two fields:

1. CollectionName --> The name of a collection.
2. Sequence --> The current sequence of a collection. The default value of it should be 0.

Everytime before inserting a new indexed model M to a collection C, we find a AutoIncrementIdModel whose CollectionName is C, and we increase its Sequence by one, then use that sequence to create M (M's id field be initialized by the sequence) and insert it to C.