feat : 문제 조회 성능 최적화 (개선) (#119)

* feat : 카테고리 필터링 추가 ( code 또는 korName 필드 조회 )

* feat : join 을 통해 n:m 관계 최적화

* feat : EAGER 즉시 로딩 사용 ( 상세조회, 이미지 )

* feat : 카테고리 필터링 추가 ( code 또는 korName 필드 조회 )

* feat : join 을 통해 n:m 관계 최적화

* feat : EAGER 즉시 로딩 사용 ( 상세조회, 이미지 )

Author: Kimminu7

src/main/java/org/ezcode/codetest/domain/problem/model/entity/Problem.java

@@ -74,7 +74,7 @@ public class Problem extends BaseEntity {
 	@OneToMany(mappedBy = "problem", cascade = CascadeType.ALL, orphanRemoval = true)
 	private List<Testcase> testcases = new ArrayList<>();
 
-	@ElementCollection(fetch = FetchType.LAZY)
+	@ElementCollection(fetch = FetchType.EAGER)
 	private List<String> imageUrl = new ArrayList<>();
 
 	@Builder

src/main/java/org/ezcode/codetest/infrastructure/persistence/repository/problem/ProblemQueryRepositoryImpl.java

@@ -4,14 +4,17 @@
 
 import org.ezcode.codetest.domain.problem.model.ProblemSearchCondition;
 import org.ezcode.codetest.domain.problem.model.entity.Problem;
+import org.ezcode.codetest.domain.problem.model.entity.QCategory;
 import org.ezcode.codetest.domain.problem.model.entity.QProblem;
+import org.ezcode.codetest.domain.problem.model.entity.QProblemCategory;
 import org.ezcode.codetest.domain.problem.model.enums.Difficulty;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageImpl;
 import org.springframework.data.domain.Pageable;
 import org.springframework.stereotype.Repository;
 
 import com.querydsl.core.BooleanBuilder;
+import com.querydsl.jpa.impl.JPAQuery;
 import com.querydsl.jpa.impl.JPAQueryFactory;
 
 import lombok.RequiredArgsConstructor;
@@ -26,32 +29,43 @@ public class ProblemQueryRepositoryImpl implements ProblemRepositoryCustom {
 	public Page<Problem> searchByCondition(Pageable pageable, ProblemSearchCondition searchCondition) {
 
 		QProblem problem = QProblem.problem;
+		QProblemCategory problemCategory = QProblemCategory.problemCategory;
+		QCategory category = QCategory.category;
 
 		// where 조건을 깔끔 하게 조립
 		BooleanBuilder builder = new BooleanBuilder();
 
 		builder.and(problem.isDeleted.isFalse());
 
-		/*
-		if(searchCondition.category() != null) {
-			builder.and(problem.categories.contains(searchCondition.category()));
+		JPAQuery<Problem> query = jpaQueryFactory
+			.selectDistinct(problem)
+			.from(problem)
+			.leftJoin(problemCategory).on(problem.eq(problemCategory.problem))
+			.leftJoin(problemCategory.category, category)
+			.where(builder);
+
+		// 카테고리 필터링
+		if (searchCondition.category() != null) {
+			builder.and(category.code.eq(searchCondition.category())
+				.or(category.korName.eq(searchCondition.category())));
 		}
-		*/
+
+		// 난이도 필터링
 		if (searchCondition.difficulty() != null) {
 			builder.and(problem.difficulty.eq(Difficulty.valueOf(searchCondition.difficulty())));
 		}
 
-		List<Problem> content = jpaQueryFactory
-			.selectFrom(problem)
-			.where(builder)
+		List<Problem> content = query
 			.offset(pageable.getOffset())
 			.limit(pageable.getPageSize())
 			.orderBy(problem.createdAt.desc())
 			.fetch();
 
 		Long total = jpaQueryFactory
-			.select(problem.count())
+			.select(problem.countDistinct())
 			.from(problem)
+			.leftJoin(problemCategory).on(problem.eq(problemCategory.problem))
+			.leftJoin(problemCategory.category, category)
 			.where(builder)
 			.fetchOne();