feat: reduce transfering extra data from database

order-service/src/main/java/com/example/orderservice/repositories/OrderRepository.java

@@ -9,6 +9,8 @@ Licensed under MIT License Copyright (c) 2021-2023 Raja Kolli.
 import com.example.orderservice.entities.Order;
 import java.util.List;
 import java.util.Optional;
+import org.springframework.data.domain.Page;
+import org.springframework.data.domain.Pageable;
 import org.springframework.data.jpa.repository.EntityGraph;
 import org.springframework.data.jpa.repository.JpaRepository;
 import org.springframework.data.jpa.repository.Modifying;
@@ -32,4 +34,7 @@ int updateOrderStatusAndSourceById(
             @Param("id") Long orderId,
             @Param("status") String status,
             @Param("source") String source);
+
+    @Query("select o.id from Order o")
+    Page<Long> findAllOrders(Pageable pageable);
 }

order-service/src/main/java/com/example/orderservice/services/OrderService.java

@@ -47,12 +47,10 @@ public PagedResult<OrderDto> findAllOrders(
 
         // create Pageable instance
         Pageable pageable = PageRequest.of(pageNo, pageSize, sort);
-        // Fetches only ParentEntities
-        Page<Order> page = orderRepository.findAll(pageable);
-        // Get orderIds matching pagination
-        List<Long> orderIds = page.getContent().stream().map(Order::getId).toList();
+        // Fetches only ParentEntities ids
+        Page<Long> page = orderRepository.findAllOrders(pageable);
         // fetching parentAlongWithChildEntries
-        List<Order> ordersWithOrderItems = orderRepository.findByIdIn(orderIds);
+        List<Order> ordersWithOrderItems = orderRepository.findByIdIn(page.getContent());
         // Mapping Order to OrderDTO CompletableFuture
         List<CompletableFuture<OrderDto>> completableFutureList =
                 ordersWithOrderItems.stream()

order-service/src/test/java/com/example/orderservice/repositories/OrderRepositoryTest.java

@@ -0,0 +1,66 @@
+/***
+<p>
+    Licensed under MIT License Copyright (c) 2023 Raja Kolli.
+</p>
+***/
+
+package com.example.orderservice.repositories;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import com.example.orderservice.common.PostGreSQLContainer;
+import com.example.orderservice.entities.Order;
+import com.example.orderservice.util.TestData;
+import java.util.ArrayList;
+import java.util.List;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.jdbc.AutoConfigureTestDatabase;
+import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
+import org.springframework.boot.testcontainers.context.ImportTestcontainers;
+import org.springframework.data.domain.Page;
+import org.springframework.data.domain.PageRequest;
+import org.springframework.data.domain.Pageable;
+import org.springframework.data.domain.Sort;
+
+@ImportTestcontainers(PostGreSQLContainer.class)
+@DataJpaTest(properties = "application.catalogServiceUrl=http://dummy")
+@AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
+class OrderRepositoryTest {
+
+    @Autowired private OrderRepository orderRepository;
+    @Autowired private OrderItemRepository orderItemRepository;
+
+    @AfterEach
+    void tearDown() {
+        this.orderItemRepository.deleteAllInBatch();
+        this.orderRepository.deleteAllInBatch();
+    }
+
+    @Test
+    void findAllOrders() {
+
+        List<Order> orderList = new ArrayList<>();
+        for (int i = 0; i <= 15; i++) {
+            orderList.add(TestData.getOrder());
+        }
+        this.orderRepository.saveAll(orderList);
+
+        // create Pageable instance
+        Pageable pageable = PageRequest.of(1, 5, Sort.by("id").ascending());
+
+        Page<Long> page = this.orderRepository.findAllOrders(pageable);
+
+        assertThat(page).isNotNull();
+        assertThat(page.getTotalElements()).isEqualTo(16);
+        assertThat(page.getTotalPages()).isEqualTo(4);
+        assertThat(page.getNumber()).isEqualTo(1);
+        assertThat(page.isFirst()).isEqualTo(false);
+        assertThat(page.isLast()).isEqualTo(false);
+        assertThat(page.hasNext()).isEqualTo(true);
+        assertThat(page.hasPrevious()).isEqualTo(true);
+        assertThat(page.getNumberOfElements()).isEqualTo(5);
+        assertThat(page.getContent()).isNotEmpty().hasSize(5);
+    }
+}