Following an example in GORM's documentation (http://gorm.io/docs/has_many.html#Has-Many), I attempted to make a User and CreditCard model with a one-to-many relation:
package main
import (
"github.com/jinzhu/gorm"
_ "github.com/jinzhu/gorm/dialects/sqlite"
"github.com/sirupsen/logrus"
)
type User struct {
gorm.Model
CreditCards []CreditCard
}
type CreditCard struct {
gorm.Model
Number string
UserID uint
}
func main() {
db, err := gorm.Open("sqlite3", "examplegorm.db")
if err != nil {
logrus.Fatalf("open db: %v", err)
}
defer db.Close()
db.LogMode(true)
db.AutoMigrate(&User{})
db.AutoMigrate(&CreditCard{})
}
However, in resulting logged SQL statements I don't see something like
CREATE TABLE credit_cards(
...
FOREIGN KEY(user_id) REFERENCES users(id)
)
as I would expect from SQLite's documentation (https://www.sqlite.org/foreignkeys.html). What I see is
> go run gorm_has_many.go
(/Users/kurt/Documents/Scratch/gorm_has_many.go:28)
[2020-01-06 09:05:58] [0.82ms] CREATE TABLE "users" ("id" integer primary key autoincrement,"created_at" datetime,"updated_at" datetime,"deleted_at" datetime )
[0 rows affected or returned ]
(/Users/kurt/Documents/Scratch/gorm_has_many.go:28)
[2020-01-06 09:05:58] [0.55ms] CREATE INDEX idx_users_deleted_at ON "users"(deleted_at)
[0 rows affected or returned ]
(/Users/kurt/Documents/Scratch/gorm_has_many.go:29)
[2020-01-06 09:05:58] [0.52ms] CREATE TABLE "credit_cards" ("id" integer primary key autoincrement,"created_at" datetime,"updated_at" datetime,"deleted_at" datetime,"number" varchar(255),"user_id" integer )
[0 rows affected or returned ]
(/Users/kurt/Documents/Scratch/gorm_has_many.go:29)
[2020-01-06 09:05:58] [0.50ms] CREATE INDEX idx_credit_cards_deleted_at ON "credit_cards"(deleted_at)
[0 rows affected or returned ]
By contrast, in an example Django project in a djangoapp app, if I have the following models.py:
from django.db import models
class User(models.Model):
name = models.CharField(max_length=255)
age = models.PositiveIntegerField()
class CreditCard(models.Model):
number = models.CharField(max_length=255)
user = models.ForeignKey('djangoapp.User', on_delete=models.CASCADE)
and I inspect the SQL statements corresponding to the creation of the CreditCard model, I do see a foreign key reference:
kurt@Kurts-MacBook-Pro-13 ~/D/S/djangoproject> python manage.py sqlmigrate djangoapp 0002_creditcard
(0.000)
SELECT name, type FROM sqlite_master
WHERE type in ('table', 'view') AND NOT name='sqlite_sequence'
ORDER BY name; args=None
(0.000) SELECT "django_migrations"."id", "django_migrations"."app", "django_migrations"."name", "django_migrations"."applied" FROM "django_migrations"; args=()
(0.000) PRAGMA foreign_keys = OFF; args=None
(0.000) PRAGMA foreign_keys; args=None
(0.000) BEGIN; args=None
CREATE TABLE "djangoapp_creditcard" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "number" varchar(255) NOT NULL, "user_id" integer NOT NULL REFERENCES "djangoapp_user" ("id") DEFERRABLE INITIALLY DEFERRED); (params None)
(0.000) PRAGMA foreign_key_check; args=None
CREATE INDEX "djangoapp_creditcard_user_id_eca64c45" ON "djangoapp_creditcard" ("user_id"); (params ())
(0.000) PRAGMA foreign_keys = ON; args=None
BEGIN;
--
-- Create model CreditCard
--
CREATE TABLE "djangoapp_creditcard" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "number" varchar(255) NOT NULL, "user_id" integer NOT NULL REFERENCES "djangoapp_user" ("id") DEFERRABLE INITIALLY DEFERRED);
CREATE INDEX "djangoapp_creditcard_user_id_eca64c45" ON "djangoapp_creditcard" ("user_id");
COMMIT;
Why is the user_id column not being generated with a REFERENCES clause like in the Django app? (It seems that GORM has an addForeignKey() method (https://github.com/jinzhu/gorm/blob/79a77d771dee4e4b60e9c543e8663bbc80466670/scope.go#L1229-L1238) but it isn't getting invoked in this example).
Update
Since it would appear that GORM's AddForeignKey() method doesn't actually get called within GORM itself, I added the following line:
db.Model(&CreditCard{}).AddForeignKey("user_id", "users(id)", "CASCADE", "CASCADE")
However, re-running the script then appears to show a syntax error:
(/Users/kurt/Documents/Scratch/gorm_has_many.go:30)
[2020-01-06 09:36:29] near "CONSTRAINT": syntax error
(/Users/kurt/Documents/Scratch/gorm_has_many.go:30)
[2020-01-06 09:36:29] [0.06ms] ALTER TABLE "credit_cards" ADD CONSTRAINT credit_cards_user_id_users_id_foreign FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE ON UPDATE CASCADE;
[0 rows affected or returned ]
