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Showing posts from July 28, 2021

Design a unique sequence with MongoDB

Greetings! If you have used RDBMS like MySQL or Oracle you know that those databases support auto-increment fields or sequences. However MongoDB's way of ID is using an ObjectId which is a large string. However if you want an unique sequence what will you do? One solution is of cause to use RDBMS solution like Oracle. Unlike NoSQL solutions, RDBMS have problems with scaling. Let's imagine that to overcome scaling problems we are using MongoDB. Why do we need a unique sequence? We will need unique sequences for several reasons. Design a hit counter. Short string generation ( Rate limiting. Easy to read identifier value. You are migrating from relational database. Eventhough MongoDB doesn't offer this feature out of box, we can implement it using it's atomic operations. The trick is to create a collection with desired name as the _id and findAndModify with $inc. db.counters.insert({ _id: "my-se