ouid

OUID - UUID based on ObjectID For Go

What & Why

MongoDB's ObjectID is a sortable unique identifier. It uses 12 bytes to store data, including a timestamp, machine identifier, process ID, and a counter.

Its hex string is more compact and readable than a UUID. However, if you directly use this string as the primary key in relational databases (Postgres, MySQL, SQLite, etc.), it can lead to index bloat and performance degradation.

Almost all relational databases natively support the UUID type, and when used as a primary key, it offers better distribution and performance characteristics compared to character types.

Coincidentally, a UUID requires 16 bytes of storage, which is 4 bytes more than an ObjectID. Therefore, we can generate a UUID by appending 4 bytes of data to an ObjectID. This way, we keep the benefits of ObjectID while gaining the performance advantages of UUID in relational databases.

OUID (ObjectUUID) is a UUID type designed based on this idea: it appends 4 bytes of empty data to the tail of an ObjectID, forming a 16-byte identifier that conforms to the UUID standard.

OUID implements the Scanner and Valuer interfaces from database/sql, so it can be used directly for read and write operations in relational databases.

In the database, it is stored as a UUID type, like this:

693a436b-4218-921b-4e0d-1e2100000000

In the application, it is represented by default as the hex string form of the ObjectID:

693a436b4218921b4e0d1e21

If needed, you can also call the OUID.UUID() method to obtain the standard UUID string representation.

If you are migrating from MongoDB to a relational database, or you want to use an ObjectID-like identifier in a relational database, OUID is a good choice.

Installation

go get github.com/unvgo/ouid