case

performance/srv/performance-service.cds

@@ -3,8 +3,8 @@ using { sap.capire.performance as my } from '../db/schema';
 service PerformanceService {
   entity OrdersHeaders as projection on my.OrdersHeaders;
   entity OrdersItems   as projection on my.OrdersItems;
-  entity Books      as projection on my.Books;
-  entity Authors      as projection on my.Authors;
+  entity Books         as projection on my.Books;
+  entity Authors       as projection on my.Authors;
 
 // static
 view OrdersItemsViewJoin as select 
@@ -66,7 +66,7 @@ from OrdersItems {*, Header.OrderNo, Header.buyer, Header.currency }
 where OrdersItems.price > 100;
 
 
-// TODO avoid CASE and/or JOIN: Denormalization of expensive complex structures, 
+// TODO avoid CASE -- Denormalization of expensive complex structures, 
 // calculate on write instead of read
 
 // CASE -> try to remodel to avoid CASE, if re-modelling is not possible, 
@@ -82,6 +82,14 @@ entity OrdersItemsCaseView as projection on OrdersItems {
 };
 
 
-
+extend my.OrdersItems with {
+    itemCategory: String enum{ Small; Medium; Large;};
+    // fill itemCategory at runtime in performance-service.js
+}
+
+entity OrdersItemsNoCaseView as projection on OrdersItems {
+    *,
+    itemCategory as category 
+};
 }
 

performance/srv/performance-service.js

@@ -5,6 +5,14 @@ class OrdersService extends cds.ApplicationService {
   init(){
     const { 'Orders.Items':OrderItems } = this.entities
 
+    // fill itemCategory at runtime
+    this.before (['CREATE', 'UPDATE'], async req =>{
+      if(req.data.quantity > 500) {req.data.itemCategory = 'Large'}
+        else if (req.data.quantity > 100) {req.data.itemCategory = 'Medium'}
+        else    {req.data.itemCategory = 'Small'}
+    })   
+    //
+
     this.before ('UPDATE', 'Orders', async function(req) {
       const { ID, Items } = req.data
       if (Items) for (let { product_ID, quantity } of Items) {