`gorm` Ignoring `sql:"index"` Tags

Why gorm is ignoring sql:"index" tags? No indexes got created.

Database in use here is PostgreSQL (importing _ "github.com/lib/pq"). This Model struct is used (because default gorm.Model uses an auto increment number - serial - as primary key and I wanted to set id myself):

type Model struct {
	ID        int64 `sql:"type:bigint PRIMARY KEY;default:0"`
	CreatedAt time.Time
	UpdatedAt time.Time
	DeletedAt *time.Time `sql:"index"`
}

And one of actual models is:

type TUHistory struct {
	Model

	TUID        int64  `json:"tu_id,string" gorm:"column:tu_id" sql:"index"`
}

func (x *TUHistory) TableName() string {
	return "tu_history"
}

And the table is created by db.CreateTable(&TUHistory{}) which creates the table correctly except for indexes.

As a temporary work around, I do db.Model(&TUHistory{}).AddIndex("ix_tuh_tu_id", "tu_id") to create indexes.

From my experience, the db.CreateTable only creates the table and it's fields. You are better off using the AutoMigrate function with the model structure that you want to migrate:

db, err := gorm.Open("postgres", connectionString)
...
// error checking
...

db.AutoMigrate(&Model)

Also, I tried AutoMigrating the model you posted and got an error saying that multiple primary keys are not allowed, so I changed the model to:

type Model struct {
	Id        int64 `sql:"type:bigint;default:0"`
	CreatedAt time.Time
	UpdatedAt time.Time
	DeletedAt *time.Time `sql:"index"`
}

and the AutoMigration created all PKs and indexes just fine.

Edit:

Checking the GORM's README, on this example, the Email structure goes as:

type Email struct {
    ID      int
    UserID  int     `sql:"index"` // Foreign key (belongs to), tag `index` will create index for this field when using AutoMigrate
    Email   string  `sql:"type:varchar(100);unique_index"` // Set field's sql type, tag `unique_index` will create unique index
    Subscribed bool
}

Notice the comment on the UserId field saying it will create the index when using AutoMigrate.

Also, it's worth taking a look at how the AutoMigrate does it's job:

// Automating Migration
db.AutoMigrate(&User{})
db.Set("gorm:table_options", "ENGINE=InnoDB").AutoMigrate(&User{})
db.AutoMigrate(&User{}, &Product{}, &Order{})
// Feel free to change your struct, AutoMigrate will keep your database up-to-date.
// AutoMigrate will ONLY add *new columns* and *new indexes*,
// WON'T update current column's type or delete unused columns, to protect your data.
// If the table is not existing, AutoMigrate will create the table automatically.