How to select first N elements Gin-Gorm-CodePudding

I have a function that displays Categories, I want to use the Preload method to also display Products related to this category, but I don’t need all the products, but only 5 pieces, how can I fix the request? Function:

func GetAllCategories(c *gin.Context) {
    Categories := []models.Categories{}
    if err := config.DB.Preload("Products").Find(&Categories).Error; err != nil {  
        c.JSON(http.StatusInternalServerError, err.Error())
    } else {
        c.JSON(http.StatusOK, gin.H{"data": &Categories})
    }
}

Categories:

type Categories struct {
    ID         uint       `json:"ID" gorm:"primaryKey"`
    Title      string     `json:"title"`
    ...
    Products   []Products `gorm:"foreignKey:CategoriesRefer" json:"products"`
}

Products:

type Products struct {
    gorm.Model
    CategoriesRefer   int64      `json:"cat_id" gorm:"column:cat_id"`
    Title             string     `json:"title" gorm:"column:title"`
    ...
}

CodePudding user response：

You can try custom preloading to modify how the Preload function is going to load Products. The code should look something like this:

func GetAllCategories(c *gin.Context) {
    Categories := []models.Categories{}
    err := config.DB.Preload("Products", func(db *gorm.DB) *gorm.DB {
             return db.Limit(5)
           }).Find(&Categories).Error 
    if err != nil {  
        c.JSON(http.StatusInternalServerError, err.Error())
    } else {
        c.JSON(http.StatusOK, gin.H{"data": &Categories})
    }
}