Struggling to manually create relations with gorm / migrate - postgresql

Question

I have an sql structure like so:
CREATE TABLE resources (
id SERIAL PRIMARY KEY,
title TEXT NOT NULL,
created_at TIMESTAMPTZ NOT NULL,
updated_at TIMESTAMPTZ NOT NULL,
deleted_at TIMESTAMPTZ
);
CREATE TABLE tags (
name TEXT PRIMARY KEY
);
What sql do I need to write, how can I tell gorm that I want a Resource to have many Tags? This is what I have currently go-wise:
package models
import (
"github.com/jinzhu/gorm"
)
type Tag struct {
Name string `gorm:"PRIMARY_KEY"`
}
type Resource struct {
gorm.Model
Title string
Tags []Tag `gorm:""`
}
Note that I explicitly do not want to auto-migrate via gorm. I am using the migrate tool to handle migrations and want to specifically handle them manually, not with go.

Answer 1

To define a has many relationship, a foreign key must exist.
So for your case Tag should be:
type Tag struct {
gorm.Model
Name string `gorm:"PRIMARY_KEY"`
ResourceID int
}
and Resource:
type Resource struct {
gorm.Model
Title string
Tags []Tag `gorm:"foreignkey:ResourceID"`
}
And your sql structure should have that foreign key ResourceID column.
Not sure if you have already checked this but it contains more details in case you need them: https://gorm.io/docs/has_many.html#Foreign-Key