I want to know how to permanently delete associations in GORM. I tried all examples shown in the documentation but I cannot get associations to become permanently deleted. For example, I am confused by GORM's documentation on deleting and clearing associations, which explicitly says: won't delete those objects from DB. (I don't understand what it means to delete objects without deleting them from the database.)
I have similar structs:
type User struct {
gorm.Model
City string `sql:"type:varchar(255);not null"`
Cards []Card `gorm:"foreignKey:UserID;constraint:OnDelete:CASCADE"`
}
type Card struct {
ID uint `gorm:"primary_key"`
UserID uint `gorm:"column:user_id"`
}
I want to execute the following SQL query in GORM form:
DELETE c
FROM cards c
JOIN users u ON c.user_id = u.id
WHERE u.name = `Madrid`
gorm.Model is including a DeletedAt field. So on deletion, this will be set to the current date, the record won't be removed from the database, but will not be findable with normal query methods. They call that "soft delete".
In order to delete the record permanently you have to use Unscoped, like:
db.Unscoped().Delete(&order)
Source: https://gorm.io/docs/delete.html
Related
I have been beating my head against this for a while now, but haven't found a reliable solution yet.
In GORM, if I have two tables
type Person struct {
Accounts []Account // hasMany relationship. Single person has many accounts
}
type Account struct {
Name string
PersonID string
}
How do I retrieve a tag that has a matching name?
I am expecting to retrieve a matching Person with given account name.
the closest I have gotten to is with
// DB is a gorm.DB struct
DB.Preload("Accounts", "name = ?", "foo").Find(&personList)
However, this does conditional preloading (duh) and not search on the joined table for a matching account name.
I am trying to customize many2many table join. I have two tables from which I want to have taken the ids and want another field, which will tell me when the entry in the join table was made. The ids are coming fine, but the "created_at" is not updating and shows "Null" instead of time.
// this is the table join struct which I want to make
type UserChallenges struct {
gorm.JoinTableHandler
CreatedAt time.Time
UserID int
ChallengeID int
}
//hook before create
func (UserChallenges) BeforeCreate(Db \*gorm.DB) error {
Db.SetJoinTableHandler(&User{}, "ChallengeId", &UserChallenges{})
return nil
}
This is not giving any error on the build. Please tell me what I am missing so that I can get the creation time field in this.
PS - The documentation of GORM on gorm.io is still showing SetupJoinTable method but it is deprecated in the newer version. There is a SetJoinTableHandler but there is no documentation available for it anywhere.
The thing to get about using a Join Table model is that if you want to access fields inside the model, you must query it explicitly.
That is using db.Model(&User{ID: 1}).Association("Challenges").Find(&challenges) or db.Preload("Challenges").Find(&users), etc. will just give you collections of the associated struct and in those there is no place in which to put the extra fields!
For that you would do:
joins := []UserChallenges{}
db.Where("user_id = ?", user.ID).Find(&joins)
// now joins contains all the records in the join table pertaining to user.ID,
// you can access joins[i].CreatedAt for example.
If you wanted also to retrieve the Challenges with that, you could modify your join struct to integrate the BelongsTo relation that it has with Challenge and preload it:
type UserChallenges struct {
UserID int `gorm:"primaryKey"`
ChallengeID int `gorm:"primaryKey"`
Challenge Challenge
CreatedAt time.Time
}
joins := []UserChallenges{}
db.Where("user_id = ?", user.ID).Joins("Challenge").Find(&joins)
// now joins[i].Challenge is populated
I want to know 2 things
I got the following structs from a similar question.
// models/school.go
type School struct {
ID int `gorm:"primary_key"`
Name string `gorm:"not null"`
Accreditations []Accreditation `gorm:"many2many:school_accreditation;"`
}
type Accreditation struct {
// "accreditation" table
ID int `gorm:"primary_key"`
Name string
Description string
}
So, by default this will create a school_accreditation table with 2 columns:
one will have School's ID
other will have Accreditation's ID
My questions:
What is the most efficient way to add another column to the school_accreditation table?
Let's say I want to have the Name field of Accreditation in the school_accreditation table.
2.1) How do I achieve this eg: school_accreditation will have school_id, accreditation_id, accreditation_name
For the 1st question,
It seems the only way of doing it by defining the SchoolAccreditation model & adding fields to it.
Also, it gives me more control over the relationship.
For the 2nd question, I am yet to find a way if there is any!
bost
For the 2nd,
You have to manually get the name from Accreditation & then add it to the column via the defined SchoolAccreditation model.
I just started to use Gorm and I am encountering troubles to define a model.
I have succeeded in creating a join table by following the doc example for self-referencing model:
type User struct {
gorm.Model
Friends []*User `gorm:"many2many:friendships;association_jointable_foreignkey:friend_id"`
}
The problem is I want an extra column in my join table to know whether a friend is accepted or not. I have looked for an answer through the internet but the only answer that I found is this :
https://github.com/jinzhu/gorm/issues/719#issuecomment-168485989
but I don't understand how I can adapt it in my case.
If anyone out there has any examples and/or solutions, I will be grateful.
Thanks again !
This answer is 4 years late but I had the same issue today so hope this helps anyone.
To add an extra column to a join table created by a self-referencing many-to-many relationship in GORM, you need to create a custom join table. In this post's case, the models would look like this:
type User struct {
gorm.Model
Friends []*User `gorm:"many2many:friends"`
}
// custom join table
type Friend struct {
UserId int `gorm:"primary_key"`
FriendId int `gorm:"primary_key"`
Accepted bool
}
Then, you use the SetupJoinTable method BEFORE you use the AutoMigrate method. This wasn't working for me until I called the join method prior to the migrate method:
err := db.SetupJoinTable(&User{}, "Friends", &Friendship{})
err = db.AutoMigrate(&User{})
This should create the join table with the extra column.
Hope this helped!
I have the following 2 structs with a many-2-many relationship.
type Message struct {
gorm.Model
Body string `tag:"body" schema:"body"`
Locations []Location `tag:"locations" gorm:"many2many:message_locations;"`
TimeSent time.Time `tag:"timesent"`
TimeReceived time.Time `tag:"timereceived"`
User User
}
type Location struct {
gorm.Model
PlaceID string `tag:"loc_id" gorm:"unique"`
Lat float64 `tag:"loc_lat"`
Lng float64 `tag:"loc_lng"`
}
If I create a Message with DB.Create(my_message), everything works fine : the Message is created in DB, along with a Location and the join message_locations table is filled with the respective IDs of the Message and the Location.
What I was expecting though was that if the Location already exists in DB (based on the place_id field, which is passed on), gorm would create the Message, retrieve the Location ID and populate message_locations.That's not what is happening.
Since the PlaceID must be unique, gorm finds that a duplicate key value violates unique constraint "locations_place_id_key" and aborts the transaction.
If on the other hand I make the PlaceID not unique, gorm creates the message alright, with the association, but then that creates another, duplicate entry for the Location.
I can test if the location already exists before trying to save the message:
existsLoc := Location{}
DB.Where("place_id = ?", mssg.Locations[0].PlaceID).First(&existsLoc)
then if true switch the association off:
DB.Set("gorm:save_associations", false).Create(mssg)
DB.Create(mssg)
The message is saved without gorm complaining, but then message_locations is not filled.
I could fill it "manually" since I've retrieved the Location ID when testing for its existence, but it seems to me it kind of defeats the purpose of using gorm in the first place.
I'm not sure what the right way to proceed might be. I might be missing something obvious, I suspect maybe something's wrong with the way I declared my structs? Hints welcome.
UPDATE 2016/03/25
I ended up doing the following, which I'm pretty sure is not optimal. If you have a better idea, please chime in.
After testing if the location already exists and it does:
// in a transaction
tx := DB.Begin()
// create the message with transaction disabled
if errMssgCreate := tx.Set("gorm:save_associations", false).Create(mssg).Error; errMssgCreate != nil {
tx.Rollback()
log.Println(errMssgCreate)
}
// then create the association with existing location
if errMssgLocCreate := tx.Model(&mssg).Association("Locations").Replace(&existLoc).Error; errMssgLocCreate != nil {
tx.Rollback()
log.Println(errMssgLocCreate)
}
tx.Commit()
In my situation I was using a UUID for the ID. I coded a BeforeCreate hook to generate the uuid. When saving a new association, there was no need for the beforeCreate hook to create a new ID, but it did so anyway (that feels a bit like it could be a bug?).
Note that it did this even when using "association" mode to append a new relationship. The behaviour was not limited to when calling Create with a nested association.
It took me several hours to debug this because when I inspected the contents of the associated records they matched exactly the instances that I had just created.
In other words:
I made a bunch of Foo
I made some Bar, and tried to attach just certain Foo to each
The Foo in the Bar relationship had the same reference as the objects I had just created.
Removing the beforeCreate hook makes the code behave like I'd expect. And happily I was already in the habit of manually making a uuid whenever needed instead of relying on it so it didn't hurt me to remove it.
I've pasted a minimally reproducible example at https://pastebin.com/wV4h38Qz
package models
import (
"github.com/google/uuid"
"gorm.io/gorm"
"time"
)
type Model struct {
ID uuid.UUID `gorm:"type:char(36);primary_key"`
CreatedAt time.Time
UpdatedAt time.Time
DeletedAt gorm.DeletedAt
}
// BeforeCreate will set a UUID rather than numeric ID.
func (m *Model) BeforeCreate(tx *gorm.DB) (err error) {
m.ID = uuid.New()
return
}
gorm:"many2many:message_locations;save_association:false"
Is getting closer to what you would like to have. You need to place it in your struct definition for Message. The field is then assumed to exist in the db and only the associations table will be populated with data.