Using Different Join Table Columns than Defaults with GORM many2many join - postgresql

Question

I'm using gorm to manage my struct to database mappings.
Right now, I have an existing schema that I'm trying to wrap in an api.
The issue is that in one of my structs, I have a many2many join through another table which doesn't use the default column names.
golang code
type AuthUser struct {
ID *int
Username *string `sql:"size:30"`
FirstName *string `sql:"size:30"`
LastName *string `sql:"size:30"`
Email *string `sql:"size:75"`
IsActive *bool
IsStaff *bool
IsSuperuser *bool
DateJoined *time.Time
LastLogin *time.Time
//ReviewsGroups ReviewsGroups `gorm:"foreignkey:group_id;associationforeignkey:user_id;many2many:reviews_group_users"`
//ReviewsGroups ReviewsGroups `gorm:"many2many:reviews_group_users"`
ReviewsGroups []ReviewsGroup `gorm:"many2many:reviews_group_users"`
}
type ReviewsGroups []ReviewsGroup
func (app *AppEnv) FindAuthUser(username string) (*AuthUser, error) {
var user AuthUser
//var groups []ReviewsGroup
//err := app.DB.Where(&AuthUser{Username: &username}).First(&user).Related(&groups).Error
err := app.DB.Preload("ReviewsGroups").Where(&AuthUser{Username: &username}).First(&user).Error
return &user, err
}
join table
rb=> \d reviews_group_users
Table "public.reviews_group_users"
Column | Type | Modifiers
----------+---------+------------------------------------------------------------------
id | integer | not null default nextval('reviews_group_users_id_seq'::regclass)
group_id | integer | not null
user_id | integer | not null
Indexes:
"reviews_group_users_pkey" PRIMARY KEY, btree (id)
"reviews_group_users_group_id_user_id_key" UNIQUE CONSTRAINT, btree (group_id, user_id)
"reviews_group_users_group_id" btree (group_id)
"reviews_group_users_user_id" btree (user_id)
Foreign-key constraints:
"group_id_refs_id_0f32ed01" FOREIGN KEY (group_id) REFERENCES reviews_group(id) DEFERRABLE INITIALLY DEFERRED
"reviews_group_users_user_id_fkey" FOREIGN KEY (user_id) REFERENCES auth_user(id) DEFERRABLE INITIALLY DEFERRED
resulting query output
[2015-10-30 09:31:32] [1.16ms] SELECT * FROM "auth_user" WHERE ("username" = 'theuser') ORDER BY "auth_user"."id" ASC LIMIT 1
[2015-10-30 09:31:32] [1.85ms] SELECT * FROM "reviews_group" INNER JOIN reviews_group_users ON reviews_group_users."reviews_group_id" = "reviews_group"."id" WHERE (auth_user_id in ('13'))
[2015-10-30 09:31:32] pq: column reviews_group_users.reviews_group_id does not exist
Any help is appreciated.
Thanks!

Answer 1

I think I can refer you to this answer => gorm Many2Many Custom table
Split the relationship into 3 tables or 3 structs if you like. AuthUser, ReviewGroup, and Group.
In your auth user you do the same as you would do with a one-to-many relationship and the same for group.
example:
type AuthUser struct {
ID *int
Username *string `sql:"size:30"`
FirstName *string `sql:"size:30"`
LastName *string `sql:"size:30"`
Email *string `sql:"size:75"`
IsActive *bool
IsStaff *bool
IsSuperuser *bool
DateJoined *time.Time
LastLogin *time.Time
ReviewsGroups []ReviewsGroup `gorm:"foreignKey:User_id;references:ID;"`
}
type Group struct {
ID uint `gorm:"primaryKey"`
param string
ReviewsGroups []ReviewsGroup
}
type ReviewGroup struct {
User_id uint `gorm:"primaryKey"`
User AuthUser `gorm:"foreignKey:ID;references:User_id"` // not necessary unless you want to be able to navigate via this model
Group_id uint `gorm:"primaryKey"`
Group AuthUser `gorm:"foreignKey:ID;references:Group_id"` // not necessary unless you want to be able to navigate via this model
param string
}
Hope it helps!