What is an ObjectId in MongoDB?

What is an ObjectId in MongoDB?

ObjectId is generated by MongoDB drivers to uniquely identify each document. The timestamp part of ObjectId allows for indirect date–based queries. The machine identifier ensures uniqueness across different machines. The process identifier helps ensure uniqueness in case of multiple operations within the same second. ObjectId is represented as a 24-character hexadecimal string. It is stored in the _id field of each document by default. ObjectId values are not sequentially generated but are designed to be globally unique....

How to Query MongoDB ObjectId by Date?

Although ObjectId is primarily used as a unique identifier, it can be used indirectly for date-based queries. However, it’s important to note that ObjectId does not store timezone information, so queries based on date will be in UTC. Below are some methods that help us to perform query MongoDB ObjectId by date as follows:...

1. Using Timestamp Range

Let’s see How to query documents in the users collection created on March 20, 2024, using MongoDB’s date range query operators $gte (greater than or equal to) and $lte (less than or equal to) with specific timestamps for the start and end of the day....

2. Using ObjectId’s First Four Bytes

Suppose we have Given a MongoDB collection of users where each document contains an _id field representing the ObjectId of the document, we need to construct an ObjectId corresponding to March 20, 2024. Using this ObjectId, we are required to query and retrieve documents created after and before March 20, 2024, from the collection....

3. Using Aggregate Framework

Let’s see How to use the MongoDB aggregation pipeline to filter documents in the users collection based on their createdAt field, selecting only those created within a specified date range?...

Conclusion

Overall, MongoDB ObjectId, primarily a unique identifier, can be indirectly used for date-based queries, offering a versatile approach to data retrieval. By leveraging the timestamp embedded within ObjectId, developers can perform date-based operations effectively. The methods discussed – using timestamp range, ObjectId’s first four bytes, and the aggregate framework – provide valuable insights into how MongoDB’s flexibility extends to date-related queries, enhancing the database’s utility in various applications....