[REFACTOR/143] 랭킹 조회시 발생하는 N+1 문제 해결

src/main/java/LuckyVicky/backend/enhance/repository/EnhanceItemRepository.java

@@ -1,10 +1,11 @@
 package LuckyVicky.backend.enhance.repository;
 
-import LuckyVicky.backend.item.domain.Item;
 import LuckyVicky.backend.enhance.domain.EnhanceItem;
+import LuckyVicky.backend.item.domain.Item;
 import LuckyVicky.backend.user.domain.User;
 import java.util.List;
 import java.util.Optional;
+import org.springframework.data.jpa.repository.EntityGraph;
 import org.springframework.data.jpa.repository.JpaRepository;
 import org.springframework.data.jpa.repository.Query;
 import org.springframework.data.repository.query.Param;
@@ -13,8 +14,14 @@ public interface EnhanceItemRepository extends JpaRepository<EnhanceItem, Long>
 
     Optional<EnhanceItem> findByUserAndItem(User user, Item item);
 
+    @EntityGraph(attributePaths = {"user"}) // N+1 문제 해결 위한 EntityGraph 방식
     @Query("SELECT e FROM EnhanceItem e WHERE e.item = :item ORDER BY e.enhanceLevel DESC, e.enhanceLevelReachedAt ASC")
     List<EnhanceItem> findEnhanceItemsByItemOrderByEnhanceLevelAndReachedTime(@Param("item") Item item);
 
+    /* N+1 문제 해결 위한 JOIN FETCH 방식
+    @Query("SELECT e FROM EnhanceItem e JOIN FETCH e.user WHERE e.item = :item ORDER BY e.enhanceLevel DESC, e.enhanceLevelReachedAt ASC")
+    List<EnhanceItem> findEnhanceItemsByItemOrderByEnhanceLevelAndReachedTime(@Param("item") Item item);
+     */
+
     Integer countByItem(Item item);
 }

src/main/java/LuckyVicky/backend/enhance/service/EnhanceItemService.java

@@ -20,6 +20,7 @@
 import java.io.IOException;
 import java.time.LocalDate;
 import java.util.List;
+import java.util.Optional;
 import lombok.RequiredArgsConstructor;
 import org.springframework.scheduling.annotation.Scheduled;
 import org.springframework.stereotype.Service;
@@ -37,9 +38,12 @@ public EnhanceItem findByUserAndItem(User user, Item item) {
                 .orElseThrow(() -> new GeneralException(ErrorCode.ENHANCE_ITEM_NOT_FOUND));
     }
 
+    public Optional<EnhanceItem> findByUserAndItemInOptional(User user, Item item) {
+        return enhanceItemRepository.findByUserAndItem(user, item);
+    }
+
     public EnhanceItem findByUserAndItemOrCreateEnhanceItem(User user, Item item) {
         return enhanceItemRepository.findByUserAndItem(user, item)
-                // 없으면 새로운 Entity 생성
                 .orElseGet(() -> {
                     Integer lastRanking = enhanceItemRepository.countByItem(item) + 1;
                     EnhanceItem newEnhanceItem = EnhanceConverter.createEnhanceItem(user, item, lastRanking);

src/main/java/LuckyVicky/backend/ranking/converter/RankingConverter.java

@@ -31,7 +31,7 @@ public static ItemRankingResDto itemRankingResDto(Item item, Integer myRanking,
         return ItemRankingResDto.builder()
                 .userRankingResDtoList(userRankingResDtoList)
                 .itemName(item.getName())
-                .myRanking(myRanking)
+                .myRanking(myRanking > 0 ? Integer.toString(myRanking) : "-")
                 .build();
     }
 

src/main/java/LuckyVicky/backend/ranking/dto/RankingResponseDto.java

@@ -1,7 +1,6 @@
 package LuckyVicky.backend.ranking.dto;
 
 import io.swagger.v3.oas.annotations.media.Schema;
-import jakarta.xml.bind.annotation.XmlType.DEFAULT;
 import java.time.LocalDate;
 import java.util.List;
 import lombok.AllArgsConstructor;
@@ -48,7 +47,7 @@ public static class ItemRankingResDto {
         private String itemName;
 
         @Schema(description = "사용자 랭킹")
-        private Integer myRanking;
+        private String myRanking;
     }
 
     // 주차별 랭킹 정보

src/main/java/LuckyVicky/backend/ranking/service/RankingService.java

@@ -13,11 +13,11 @@
 import LuckyVicky.backend.ranking.dto.RankingResponseDto.UserRankingResDto;
 import LuckyVicky.backend.ranking.dto.RankingResponseDto.WeekRankingResDto;
 import LuckyVicky.backend.user.domain.User;
-import jakarta.transaction.Transactional;
+import java.time.LocalDate;
 import java.time.temporal.WeekFields;
 import java.util.List;
 import java.util.Locale;
-import java.time.LocalDate;
+import java.util.Optional;
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Service;
 
@@ -44,14 +44,15 @@ public ItemRankingResDto getItemRankingResDto(User user, Item item) {
         List<EnhanceItem> enhanceItemList =
                 enhanceItemRepository.findEnhanceItemsByItemOrderByEnhanceLevelAndReachedTime(item);
 
-        Integer myRanking = enhanceItemService.findByUserAndItemOrCreateEnhanceItem(user, item).getRanking();
+        Optional<EnhanceItem> enhanceItem = enhanceItemService.findByUserAndItemInOptional(user, item);
+        Integer myRanking = enhanceItem.map(EnhanceItem::getRanking).orElse(-1);
 
         List<UserRankingResDto> userRankingResDtoList
                 = enhanceItemList.stream()
                 .map(RankingConverter::userRankingResDto)
                 .toList();
 
-        return RankingConverter.itemRankingResDto(item, myRanking ,userRankingResDtoList);
+        return RankingConverter.itemRankingResDto(item, myRanking, userRankingResDtoList);
     }
 
     public WeekRankingResDto getWeekRankingResDto(User user, List<Item> weekItemList, LocalDate date) {
@@ -67,15 +68,16 @@ public WeekRankingResDto getWeekRankingResDto(User user, List<Item> weekItemList
         LocalDate enhanceStartDate = weekItemList.get(0).getEnhanceStartDate();
         LocalDate enhanceEndDate = weekItemList.get(0).getEnhanceEndDate();
 
-        return RankingConverter.weekRankingResDto(enhanceMonthWeek, itemRankingResDtoList, enhanceStartDate, enhanceEndDate);
+        return RankingConverter.weekRankingResDto(enhanceMonthWeek, itemRankingResDtoList, enhanceStartDate,
+                enhanceEndDate);
     }
 
     public CurrentItemRankingResDto getCurrentItemRankingResDto(Item item, EnhanceItem enhanceItem) {
         List<EnhanceItem> enhanceItemList =
                 enhanceItemRepository.findEnhanceItemsByItemOrderByEnhanceLevelAndReachedTime(item);
 
         List<UserRankingResDto> userRankingResDtoList
-                 = enhanceItemList.stream()
+                = enhanceItemList.stream()
                 .map(RankingConverter::userRankingResDto)
                 .toList();
 

src/main/resources/application.yml

@@ -77,12 +77,12 @@ spring:
     properties:
       hibernate:
         dialect: org.hibernate.dialect.MySQLDialect
-        #        format_sql: true
-        #        show_sql: true
+        format_sql: true
+        show_sql: true
         use_sql_comments: true
         hbm2ddl:
           auto: update
-        default_batch_fetch_size: 1000
+        default_batch_fetch_size: 100
 
 ---
 
@@ -108,4 +108,4 @@ spring:
         use_sql_comments: true
         hbm2ddl:
           auto: update
-        default_batch_fetch_size: 1000
+        default_batch_fetch_size: 100