I'm new to go and Backend and I'm Trying to make many-to-many relation between tables. I used this repo to make model:https://github.com/harranali/gorm-relationships-examples/tree/main/many-to-many
I Used GORM with postgresql.
My model:
type Book struct {
gorm.Model
Title string `json:"title"`
Author string `json:"author"`
Description string `json:"description"`
Category string `json:"Category"`
Publisher string `json:"publisher"`
AuthorsCard []*AuthorsCard `gorm:"many-to-many:book_authorscard;" json:"authorscard"`
}
type AuthorsCard struct {
gorm.Model
Name string `json:"name"`
Age int `json:"age"`
YearOfBirth int `json:"year"`
Biography string `json:"biography"`
}
After connecting to database and AutoMigrating:
func init() {
config.Connect()
db = config.GetDB()
db.AutoMigrate(&models.Book{}, &models.AuthorsCard{})
}
I've created Function to see how that relation works:
func TestCreate() {
var AuthorsCard = []models.AuthorsCard{
{
Age: 23,
Name: "test",
YearOfBirth: 1999,
Biography: "23fdgsdddTEST",
},
}
db.Create(&AuthorsCard)
var testbook = models.Book{
Title: "Test",
Author: "tst",
Description: "something",
}
db.Create(&testbook)
db.Model(&testbook).Association("AuthorsCard").Append(&AuthorsCard)
}
But got This Error:
panic: reflect: call of reflect.Value.Interface on zero Value [recovered]
panic: reflect: call of reflect.Value.Interface on zero Value
How can I deal with this "Null" problem and make proper relation?
UPD: The First part of a problem was connected to a version of GORM, After I changed old version(github.com/jinzhu/gorm v1.9.16) to new version (gorm.io/gorm v1.23.6) the problem with reflect Error gone.
but now, when I want to create new book, I get this Error:
/go/pkg/mod/gorm.io/driver/postgres#v1.3.7/migrator.go:119 ERROR: there is no unique constraint matching given keys for referenced table "authors_cards" (SQLSTATE 42830)
[28.440ms] [rows:0] CREATE TABLE "book_authorscard" ("book_id" bigint,"authors_card_id" bigint,PRIMARY KEY ("book_id","authors_card_id"),CONSTRAINT "fk_book_authorscard_authors_card" FOREIGN KEY ("authors_card_id") REFERENCES "authors_cards"("id"),CONSTRAINT "fk_book_authorscard_book" FOREIGN KEY ("book_id") REFERENCES "books"("id"))
[GIN-debug] [WARNING] Creating an Engine instance with the Logger and Recovery middleware already attached.
UPD 2:
I decided to make a Migrator().DropTable(). That's kinda worked, and all Errors have gone. But still I get "authorscard": null as a response.
By reading the release note of Gorm v2 (https://gorm.io/docs/v2_release_note.html), I think that you are trying to use v2 feature with an old version (<v2). Try to use Gorm latest version.
Related
I'm attempting to use Prisma with Cockroachdb locally. I understand that official support for CockroachDB is in the works.
I have a parallel local PostgreSQL database where everything is working correctly and I am able to generate Prisma migrations to run manually against Cockroachdb. All of this works and I end up with two apparently identical schemas.
However, any create operation in Prisma using the connect feature is failing with the following error:
Invalid `prisma.mylinkedtable.create()` invocation:
Foreign key constraint failed on the field: `(not available)`
Here are key parts of my schema.prisma:
datasource db {
provider = "postgresql"
url = "postgresql://user:pass#localhost:26257/mydb"
}
generator client {
provider = "prisma-client-js"
previewFeatures = ["cockroachdb"]
}
model MyLinkedEntity {
id Int #id #default(autoincrement())
myEntity MyEntity #relation(fields: [myEntityId], references: [id])
myEntityId Int
// ...
}
model MyEntity {
id Int #id #default(autoincrement())
// ...
}
The code that is triggering the foreign key constraint:
const entity = await prisma.myEntity.findFirst({})
await prisma.myLinkedEntity.create({
data: {
myEntityId: entity.id,
// ...
}
}
If I go about it slightly diffently and try to link using the connect feature:
await prisma.myLinkedEntity.create({
data: {
myEntity: {
connect: {
id: entity.id
}
},
// ...
}
}
I get a different error:
Invalid `prisma.myLinkedEntity.create()` invocation:
An operation failed because it depends on one or more records that were required but not found. No 'MyEntity' record(s) (needed to inline the relation on 'MyLinkedEntity' record(s)) was found for a nested connect on one-to-many relation 'MyEntityToMyLinkedEntity'.
What gives?
It looks like the related rows are not being created first.
Could you try using connectOrCreate instead? https://www.prisma.io/docs/concepts/components/prisma-client/relation-queries#connect-or-create-a-record
It could also be something wrong with the Prisma model. I'm not not sure if order matters, but I notice you have the relation defined before the ID it's referencing.
One final, unrelated, point: you should not use auto incrementing ints as keys in CockroachDB. See https://www.cockroachlabs.com/docs/v21.2/schema-design-table#primary-key-best-practices
I am trying to use the official mongodb driver in golang and am seeing something unexpected.
If I have a struct like
type User struct {
ID primitive.ObjectID `json:"id" bson:"_id"`
Name string `json:"name" bson:"name"`
Email string `json:"email" bson:"email"`
}
I create a new instance of this with Name and Email but omit ID expecting that the DB will fill this with its value. Instead it uses all zeroes and so the second and so on inserts fail with
multiple write errors: [{write errors: [{E11000 duplicate key error collection: collection.name index: _id_ dup key: { : ObjectId('000000000000000000000000') }}]}, {<nil>}]
If I use a *primitive.ObjectID I get the same class of error only on null instead of zeroes
multiple write errors: [{write errors: [{E11000 duplicate key error collection: collection.name index: _id_ dup key: { : null }}]}, {<nil>}]
It doesn't matter if I use the omitempty directive or not, same result.
If I omit the ID field entirely, it works, but then my struct doesn't have that data on it.
Is there a way to have the DB handle the ID? Or MUST I explicitly call the NewObjectID() function on the struct?
It doesn't matter if I use the omitempty directive or not, same result.
omitempty tag on ID should work. For example:
type User struct {
ID primitive.ObjectID `json:"id" bson:"_id,omitempty"`
Name string `json:"name" bson:"name"`
Email string `json:"email" bson:"email"`
}
collection.InsertOne(context.Background(), User{Name:"Foo", Email:"Baz"})
If you don't specify the omitepmty tag, then the behaviour that you observed is just Go structs behaviour; whereby if any of struct fields are omitted it will be zero-valued. In this case because you have specified the field type to be primitive.ObjectID, ObjectId('000000000000000000000000') is the zero value.
This is the reason why you need to generate a value first before inserting, i.e.:
collection.InsertOne(context.Background(),
User{ ID: primitive.NewObjectID(),
Name: "Foo",
Email: "Bar"})
Is there a way to have the DB handle the ID?
Technically, it's the MongoDB driver that automatically generates the ObjectId if it's not supplied before sending to server.
You can try to use bson.M instead of a struct when inserting to leave out the _id field, i.e.
collection.InsertOne(context.Background(),
bson.M{"name":"Foo", "email":"Bar"})
Code snippet above is written using mongo-go-driver v1.3.x
The omitempty struct tag should work:
type User struct {
ID primitive.ObjectID `json:"id" bson:"_id,omitempty"`
Name string `json:"name" bson:"name"`
Email string `json:"email" bson:"email"`
}
The primitive.ObjectID type implements the bsoncodec.Zeroer interface, so it should be omitted from the document if it's the empty object ID (all 0's) and the driver will generate a new one for you. Can you try this and post the output?
I'm trying to setup relation between two models on PostgreSQL database using Go and gorm.
Here is my code, first model:
Trip.go
package model
import "github.com/jinzhu/gorm"
// Trip models
type Trip struct {
gorm.Model
TripName string
TripDescription string
}
Second model:
TripKeyPoints.go
package model
import "github.com/jinzhu/gorm"
// TripKeyPoint models
type TripKeyPoint struct {
gorm.Model
KPName string
KPDescription string
TripID Trip
}
Part of code from a file which runs migrations and initializes all
db.DropTableIfExists(&User{}, &model.Trip{}, &model.TripKeyPoint{})
db.AutoMigrate(&User{}, &model.Trip{}, &model.TripKeyPoint{})
db.Model(&model.TripKeyPoint{}).AddForeignKey("trip_id", "trips(id)", "CASCADE", "CASCADE")
Users models is just an addon but I leave it in this snippet.
Due to many tests, I drop tables at the beginning.
Here is what I receive when i run the code:
?[35m(C:/golang_lab/golang-gorm-tutorial/users.go:36)?[0m
?[33m[2019-09-21 18:40:34]?[0m ?[31;1m pq: column "trip_id" referenced in foreign key constraint does not exist ?[0m
And yeah that's true, when I log into postgres in table trip_key_points there isn't column with a foreign key.
What I need to do, I want to have one TRIP object and then assign other TripKeyPoints.
Any idea what why? Or how can I force GORM to create this column?
I explicitly define foreign key column:
// TripKeyPoint models
type TripKeyPoint struct {
gorm.Model
KPName string
KPDescription string
TripID uint `gorm:"TYPE:integer REFERENCES trips"`
}
try to edit your struct like this :
// TripKeyPoint models
type TripKeyPoint struct {
gorm.Model
KPName string
KPDescription string
TripID Trip `gorm:"foreignkey:TripId"`
}
I have a Task type that has a list of Runner type objects in it. I am trying to map it to database using golang gorm but it doesn't have foreign key and i am getting invalid association during migration
My Task struct:
type Task struct {
gorm.Model
Name string `gorm:"not null;unique_index"`
Description string
Runners []Runner
}
My Runner struct:
type Runner struct {
gorm.Model
Name string `gorm:"not null;unique"`
Description string
}
My migration code:
func migrateSchema () (err error) {
db, err := context.DBProvider()
if err != nil {
return
}
db.Model(&Task{}).Related(&Runner{})
db.AutoMigrate(&Task{})
db.AutoMigrate(&Runner{})
return
}
On db.AutoMigrate(&Task{}) I get invalid association message in console and when I check the database there is no foreign key created or no reference field created on runners table
What am I doing wrong?
I had a similar issue, and it took me forever to figure it out. I believe the GORM documentation could definitely be better. Here's the relevant code snippet from the GORM site:
//User has many emails, UserID is the foreign key
type User struct {
gorm.Model
Emails []Email
}
type Email struct {
gorm.Model
Email string
UserID uint
}
db.Model(&user).Related(&emails)
//// SELECT * FROM emails WHERE user_id = 111; // 111 is user's primary key
Why your code isn't working:
First you need to add a TaskID field to your Runner struct.
db.Model(&Task{}).Related(&Runner{}) doesn't do what you think it does. If you look at the code snippet from GORM, the SELECT comment kind of explains it (not very well though). The example is assuming that the &user is already populated and has an ID of 111, then it fetches the emails storing them in &emails that match the UserID of &user.
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.
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
}
For postgresql, here is what I did:
go get github.com/google/uuid
Use uuid.UUID (from "github.com/google/uuid"), as type,
e.gID uuid.UUID `gorm:"type:uuid;default:uuid_generate_v4()"`
Add uuid-ossp extension for postgres database,
e.g
CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
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.
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
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:
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.
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)
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()"`
}