Implementation of UUID and binary(16) in gorm v2.

Using Customized Data Types

Hello Developers 👋. In this article, I will demonstrate how we can make use of UUID and Binary(16) datatype in gorm v2 and golang.

What is UUID?

A UUID is just a 128-bit value and it is usually represented in human-readable format as an UTF8 string composed of 5 groups of hexadecimal charac ters separated by dashes.

Example: cef4c20c-30cf-11eb-9242–9822ef9cf075

Pros of using UUID instead of AUTO_INCREMENT PRIMARY KEY?

1. They are unique across tables, databases, and servers.
2. They are hard(er) to guess from URLs.

Cons of using UUID:

1. Increased Storage i.e. 36 characters and thus performance issues.
2. It is more difficult to debug.

For more details visit here

Looking at the both pros and cons of UUID, we will work with UUID programmatically in our golang and gorm implementation but we will save it as a binary(16) in the database for better compactness.

Let's start our demonstration

We will be using the following packages.

go get -u gorm.io/gorm
go get -u gorm.io/driver/mysql
go get -u github.com/google/uuid

Problem

Since we will be using binary(16) as our column type for ID. There is no built-in support for performing queries for binary datatype in gorm . And binary is not in a human-readable format too. So we will be using UUID for development(gorm and golang code) but use binary for storage in the database.

So we need different conversions to be done during the insertion and retrieval of data to and from the database. We will implement our own custom data type for this purpose. I will name MYTYPE as a custom type.

Implementing Customized Data Type

Let's discuss the above code briefly

Any Custom Data Type must implement Scanner and Value interface so that Gorm knows how to receive and save into the database.

[Line 1-2]: Here we create a new type MYTYPE as uuid.UUID.

[Line 4–8]: StringToMYTYPE is the helper function to convert the string representation of UUID to our custom data type.

[Line 19–29]: Here marshaling and unmarshaling logic are implemented for our custom data type.

[Line 15–18]: GormDataType function tells which data type to be used during the migration of the table. In our case we want binary(16) .

[Line 31–38]: Scan function tells the GORM how to receive data from the database. Here we are expecting []byte from the database and are converting to uuid.UUID for easier usage.

For Example

[]byte ➡️ [151 77 149 200 247 16 68 202 171 131 192 137 149 72 249 229]
uuid.UUID ➡️ cef4c20c-30cf-11eb-9242–9822ef9cf075

[Line 40–43]: Value function tell the GORM how to save data to the database. This is the reverse conversion from above.

Model

For the demonstration purpose, we will create two relatable models with relation.

A Post has many Comments

We created two models Post and Comment. Here we have used UUID_TO_BIN(UUID()) MySQL function to generate binary(16)

UUID()️ ➡️ d15f093b-30d3–11eb-9242–9822ef9cf075

UUID_TO_BIN(UUID()) ➡️ 0xde9dde9330d311eb92429822ef9cf075

Database

Here we are configuring the MySQL gorm connection. We are also auto migrating our two previously made model Post and Comment.

Adding New Post in Database

After creating a new Post, if we print post.ID we get

[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]

Here we don’t get the actual id of the post just created. This only works for the auto-increment column in MySQL[I think].

Currently, we are using UUID_TO_BIN(UUID()) MySQL function to generate Binary(16). But now we will manually create uuid and insert it during any new post creation using BeforeCreate hook. This implementation will solve our previous problem i.e retrieving the recently created id of the post

BeforeCreate Hook

Final Main Program

Let's discuss this code briefly

• [Line 1–6]: We here create our new Post.
• [Line 8–13]: We receive the id of the recently created post using post.ID . Then Create a comment on that post.
• [Line 15–18]: Here we demonstrate the where query to retrieve recently created Post with its comment.

Table `posts`

Table `comments`

CONCLUSION

If you get lost on any part you can check these github projects.

GitHub - dipeshhkc/gorm-binary-16-uuid

dipeshdulal/binary-uuid-gorm

That’s it for this article. This is the end of our short journey with the implementation of UUID and binary(16) custom datatype in gorm. Hope this will help you with your project. Any kind of suggestions would be highly appreciable. Happy Coding 💻.