Panel.go Relationship Expert

Expert in implementing database relationships for Panel.go with BelongsTo, HasMany, HasOne, BelongsToMany, and polymorphic relationships.

Expertise

• •BelongsTo: One-to-one, child to parent (Post belongs to User)
• •HasOne: One-to-one, parent to child (User has one Profile)
• •HasMany: One-to-many (User has many Posts)
• •BelongsToMany: Many-to-many (Post belongs to many Tags)
• •MorphTo: Polymorphic relationships
• •Eager Loading: Preload, Joins to prevent N+1

Quick Patterns

BelongsTo

type Post struct {
    ID     uint
    UserID uint
    User   *User `gorm:"foreignKey:UserID;constraint:OnUpdate:CASCADE,OnDelete:CASCADE"`
}

fields.Link("user", &user.UserResource{}).DisplayKey("name")

HasMany

type User struct {
    ID    uint
    Posts []Post `gorm:"foreignKey:UserID"`
}

fields.Collection("posts", &post.PostResource{}).DisplayKey("title")

BelongsToMany

type Post struct {
    ID   uint
    Tags []Tag `gorm:"many2many:post_tags;"`
}

fields.Connect("tags", &tag.TagResource{}).DisplayKey("name")

Eager Loading

func (r *PostResource) With() []string {
    return []string{"User", "Category", "Tags"}
}

Key Rules

• •Always index foreign keys
• •Use Preload to prevent N+1 queries
• •Define cascade rules (CASCADE, RESTRICT, SET NULL)
• •Set DisplayKey for relationships
• •Add With() method for eager loading

Usage

When user asks to add relationships:

1. •Add foreign key to entity
2. •Add relationship field with GORM tags
3. •Add relationship field to field resolver
4. •Set DisplayKey
5. •Add eager loading in With() method

Anti-Patterns

❌ Don't forget foreign key indexes - Always index foreign keys ❌ Don't skip eager loading - Use With() to prevent N+1 queries ❌ Don't forget DisplayKey - Set DisplayKey for relationship fields ❌ Don't skip cascade rules - Define OnUpdate and OnDelete behavior ❌ Don't use wrong field types - Link for BelongsTo, Collection for HasMany, Connect for BelongsToMany

Sharp Edges

⚠️ N+1 Queries: Always use Preload or Joins for relationships ⚠️ Cascade Deletes: Be careful with CASCADE on delete ⚠️ Many-to-Many: Requires junction table (many2many tag) ⚠️ DisplayKey: Must match actual field name in related entity ⚠️ Polymorphic: Use MorphTo for polymorphic relationships