How do you do UUID in Golangs Gorm?

I have the following model...

type User struct {
    ID        string  `sql:"type:uuid;primary_key;default:uuid_generate_v4()"`
	FirstName string `form:"first_name" json:"first_name,omitempty"`
	LastName  string `form:"last_name" json:"last_name,omitempty"`
	Password  string `form:"password" json:"password" bindind:"required"`
	Email     string `gorm:"type:varchar(110);unique_index" form:"email" json:"email,omitempty" binding:"required"`
	Location  string `form:"location" json:"location,omitempty"`
    Avatar    string `form:"avatar" json:"avatar,omitempty"`
    BgImg     string `form:"bg_img" json:"bg_img,omitempty"`
    CreatedAt time.Time
    UpdatedAt time.Time
    DeletedAt time.Time
}

I've tried several different ways, but this way throws (pq: relation "users" does not exist). I have no related models, it's literally just that one model.

I've tried using...

func (user *User) BeforeCreate(scope *gorm.Scope) error {
	scope.SetColumn("ID", uuid.NewV4())
	return nil
}

Along with a uuid lib, but had no luck with that either.

For postgresql, here is what I did:

• go get github.com/google/uuid
• Use uuid.UUID (from "github.com/google/uuid"), as type,
  e.g
  <pre>ID uuid.UUID gorm:"type:uuid;default:uuid_generate_v4()"</pre>
• Add uuid-ossp extension for postgres database,
  e.g
  <pre>CREATE EXTENSION IF NOT EXISTS "uuid-ossp";</pre>
• Then, when you call DB's Create() method, the uuid is generated automatically.

Update: pg14+ gen_random_uuid()

(as mentioned in Doron Segal's comment)

pg 14 has built-in function gen_random_uuid() to generate uuid v4, e.g:

create table:
> create table uuid_test (uid text default gen_random_uuid());

insert a row:

> insert into uuid_test(uid) values (DEFAULT);

Then uid column is generated automatically.

Similiar, in go you can use the function as defaul value I think, e.g:
> ID uuid.UUID gorm:"type:uuid;default:gen_random_uuid()"

BTW, the gen_random_uuid() function only support uuid v4 now, to use other versions, you still need uuid-ossp extension.

Turns out I was trying to store the UUID as the wrong type, I was doing...

func (user *User) BeforeCreate(scope *gorm.Scope) error {
	scope.SetColumn("ID", uuid.NewV4())
	return nil
}

When it needed to be...

func (user *User) BeforeCreate(scope *gorm.Scope) error {
    scope.SetColumn("ID", uuid.NewV4().String())
    return nil
}

This was my solution for Gorm v1.21

go get gorm.io/gorm
go get gorm.io/driver/postgres
go get github.com/google/uuid

import (
  "gorm.io/gorm"
  "github.com/google/uuid"
)

type User struct {
  Id string `gorm:"primaryKey"`
}

// Note: Gorm will fail if the function signature
//  does not include `*gorm.DB` and `error`

func (user *User) BeforeCreate(tx *gorm.DB) (err error) {
  // UUID version 4
  user.Id = uuid.NewString()
  return
}

Notes:

1. For the Google UUID package, the methods uuid.New() and uuid.NewString() use UUID version 4. This is not clearly stated in the documentation (http://pkg.go.dev/github.com/google/uuid), but by looking into the source code, you can see that these are wrappers around uuid.NewRandom() which is stated as being UUID version 4.

2. While some recommend the Satori UUID package (https://github.com/satori/go.uuid), benchmarks show that it has 3.3x lower performance than the Google UUID package
   (https://gist.github.com/mattes/69a4ab7027b9e8ee952b5843e7ca6955)

For this you will need gorm and go.uuid

go get github.com/jinzhu/gorm

go get github.com/satori/go.uuid

Try creating your own model base model in place of gorm.Model like so:

type Base struct {
 ID         string     `sql:"type:uuid;primary_key;default:uuid_generate_v4()"`
 CreatedAt  time.Time  `json:"created_at"`
 UpdatedAt  time.Time  `json:"updated_at"`
 DeletedAt  *time.Time `sql:"index" json:"deleted_at"`
}

You would then populate this field using a method called before creation of any record, like so:

func (base *Base) BeforeCreate(scope *gorm.Scope) error {
 id, err := uuid.NewV4()
 if err != nil {
   return err
 }
 return scope.SetColumn("ID", uuid.String())
}

Therefore, for your particular case, you would have:

type User struct {
    Base
    FirstName string `form:"first_name" json:"first_name,omitempty"`
    LastName  string `form:"last_name" json:"last_name,omitempty"`
    Password  string `form:"password" json:"password" bindind:"required"`
    Email     string `gorm:"type:varchar(110);unique_index" form:"email" json:"email,omitempty" binding:"required"`
    Location  string `form:"location" json:"location,omitempty"`
    Avatar    string `form:"avatar" json:"avatar,omitempty"`
    BgImg     string `form:"bg_img" json:"bg_img,omitempty"`
}

More details on this can be found here

The error (pq: relation "users" does not exist) usually means that, the table users does not exists in the database. It has nothing to do with the relationship between two models.

So basically, You first need to create the table in the database (Or auto migrate the database As per @Apin suggest). And try to re-run the same code.

None of these worked for me using gorm v1.21.
Here was my solution. Note that I'm using the satori/go.uuid library for generating UUID, but code with google's library is near identical.

type UUIDBaseModel struct {
	ID        uuid.UUID       `gorm:"primary_key" json:"id"`
	CreatedAt time.Time  `json:"created_at"`
	UpdatedAt time.Time  `json:"updated_at"`
	DeletedAt *time.Time `sql:"index" json:"deleted_at"`
}

func (base *UUIDBaseModel) BeforeCreate(tx *gorm.DB) error {
	uuid := uuid.NewV4().String()
	tx.Statement.SetColumn("ID", uuid)
	return nil
}

Now I used Gorm 2.0 and this worked:

go get github.com/satori/go.uuid 

type Tablename struct {
 ID         string     `sql:"type:uuid;primary_key;default:uuid_generate_v4()"`
 }

With MySQL 8.0 and gorm (gorm.io/driver/mysql v1.5.0 and gorm.io/gorm v1.25.1):

type ModelUUID struct {
	ID        string         `gorm:"type:binary(16);column:id;primaryKey;default:(UUID_TO_BIN(UUID(), 1));" json:"id" validate:"required"`
	CreatedAt time.Time      `json:"createdAt"`
	UpdatedAt time.Time      `json:"-"`
	DeletedAt gorm.DeletedAt `json:"-" gorm:"index" swaggerignore:"true"`
}