go – Unable to set foreign key using gorm Postgresql-ThrowExceptions

Exception or error:

I’m building a Golang backend using jinzhu/gorm and I’m having some troubles trying to set up a relation between two tables e.g. Items and Manufacturers using a foreign key.

I’m following the steps at jinzhu.me/gorm/models but I’m honestly finding myself puzzled coming from a more straightforward approach of manually writing tables etc, for instance, using go pq.

item.go:

package model

import "github.com/jinzhu/gorm"

type Item struct {
    gorm.Model
    Item         string       `gorm:"primary_key"`
    Manufacturer Manufacturer `gorm:"ForeignKey:Name"`
}

manufacturer.go:

package model

import "github.com/jinzhu/gorm"

type Manufacturer struct {
    gorm.Model
    Name string `gorm:"primary_key"`
}

I get no errors nor warnings. Inspecting my tables I noticed no correlation was created. Item does not have Manufacturer field.

What I tried so far:

  • Not explicitly writing gorm:"ForeignKey:Name" since Manufacturer field is already a Manufacturer
  • Writing gorm:"ForeignKey:Name;AssociationForeignKey:Name"
  • Manually associating them with db.Model(&model.Item{}).Related(&model.Manufacturer{})
  • Manually associating them with db.Model(&model.Item{}).Related(&model.Manufacturer{}, "Manufacturer")
  • Manually associating them with db.Model("items").Related("manufacturers"). They get created with this name on Postgresql even though their model’s name is singular.

EDIT:

Trying something like

type Item struct {
    Item             string       `gorm:"primary_key"`
    Manufacturer     Manufacturer
    ManufacturerID   int
}

type Manufacturer struct {
    ID uint
    Name string
}

Leads to the same result. No foreign key is created and I’m able to insert new items with a non-existent Manufacturer.

What Am I doing wrong? Am I missing something?

How to solve:

You have to do something like:

type Item struct {
    gorm.Model
    Item         string       `gorm:"primary_key"`
    ManufacturerName string   `sql:"type:varchar REFERENCES manufacturers(name)"`
    Manufacturer Manufacturer `gorm:"ForeignKey:ManufacturerName;AssociationForeignKey:Name`
}

To tell it to a) Use ManufacturerName as the foreign key, and B) use Name on the other table.

Or you can just do:

type Item struct {
    gorm.Model
    Item         string       `gorm:"primary_key"`
    ManufacturerID uint       `sql:"type:uint REFERENCES manufacturers(id)"`
    Manufacturer Manufacturer `gorm:"ForeignKey:Man;AssociationForeignKey:Name"`
}

Answer´╝Ü

I couldn’t get any of the solutions I found working for this while following gorm’s documentation / googling / stack overflow. Here’s what worked for me:

I have a Call object & TranscriptItem object.

A call can have many transcript items but a transcript item can only have one call.

Call object

type Call struct {
    gorm.Model
    DialInNumber      string
}

Transcript object

type TranscriptItem struct {
    gorm.Model
    Transcript string
    CallID     uint
}

I have my auto migration and a manual AddForeignKey migration

    db.AutoMigrate(&Call{}, &TranscriptItem{})
    db.Model(&TranscriptItem{}).AddForeignKey("call_id", "calls(id)", "RESTRICT", "RESTRICT")

I would’ve preferred to use the mechanics outlined in gorm’s documentation, but at the end of the day I just needed something that worked.

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