perf: optimize ListProducts, ListCategories, and ListOrders GORM queries with select-specific-columns and custom nested preload column selects

controllers/order_controller.go

@@ -248,7 +248,16 @@ func ListOrders(c *gin.Context) {
 	skip, _ := strconv.Atoi(skipStr)
 	limit, _ := strconv.Atoi(limitStr)
 
-	query := config.DB.Preload("Branch").Preload("Items.Product").
+	query := config.DB.Select("id, company_id, branch_id, order_number, total_amount, paid_amount, change_amount, payment_method, payment_status, midtrans_order_id, midtrans_token, created_at").
+		Preload("Branch", func(db *gorm.DB) *gorm.DB {
+			return db.Select("id, name")
+		}).
+		Preload("Items", func(db *gorm.DB) *gorm.DB {
+			return db.Select("id, order_id, product_id, quantity, unit_price, subtotal")
+		}).
+		Preload("Items.Product", func(db *gorm.DB) *gorm.DB {
+			return db.Select("id, name")
+		}).
 		Where("company_id = ?", *user.CompanyID).
 		Order("created_at desc")
 

controllers/product_controller.go

@@ -11,6 +11,7 @@ import (
 	"service-warungpos-go/services"
 
 	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
 )
 
 // DTOs untuk Kategori & Produk
@@ -99,7 +100,7 @@ func ListCategories(c *gin.Context) {
 	}
 
 	var allCategories []models.Category
-	if err := config.DB.Where("company_id = ?", *user.CompanyID).Find(&allCategories).Error; err != nil {
+	if err := config.DB.Select("id, company_id, name, description, created_at").Where("company_id = ?", *user.CompanyID).Find(&allCategories).Error; err != nil {
 		c.JSON(http.StatusInternalServerError, gin.H{"detail": "Gagal mengambil data kategori"})
 		return
 	}
@@ -297,7 +298,11 @@ func ListProducts(c *gin.Context) {
 	limitStr := c.Query("limit")
 	skipStr := c.Query("skip")
 
-	query := config.DB.Preload("Category").Where("company_id = ?", *user.CompanyID)
+	query := config.DB.Select("id, company_id, category_id, name, sku, price, stock, is_unlimited_stock, image_url, is_active, created_at, updated_at").
+		Preload("Category", func(db *gorm.DB) *gorm.DB {
+			return db.Select("id, name")
+		}).
+		Where("company_id = ?", *user.CompanyID)
 
 	if activeOnly {
 		query = query.Where("is_active = ?", true)