[fix] 라운드 변경 시 question 조회에 join 적용

backend/src/main/java/io/f1/backend/domain/game/dto/request/QuizChangeRequest.java

@@ -8,7 +8,6 @@
 import io.f1.backend.domain.game.model.Room;
 import io.f1.backend.domain.game.websocket.MessageSender;
 import io.f1.backend.domain.quiz.app.QuizService;
-import io.f1.backend.domain.quiz.entity.Quiz;
 
 import lombok.extern.slf4j.Slf4j;
 
@@ -20,11 +19,8 @@ public boolean change(Room room, QuizService quizService) {
         if (room.getQuizId() == quizId) {
             return false; // 동일하면 무시
         }
-        Quiz quiz = quizService.getQuizWithQuestionsById(quizId);
-        int questionSize = quiz.getQuestions().size();
-        room.changeQuiz(quiz);
-        // 퀴즈의 문제 갯수로 변경
-        room.changeRound(questionSize, questionSize);
+        Long questionsCount = quizService.getQuestionsCount(quizId);
+        room.changeQuiz(quizId, questionsCount.intValue());
         return true;
     }
 

backend/src/main/java/io/f1/backend/domain/game/dto/request/RoundChangeRequest.java

@@ -3,7 +3,6 @@
 import io.f1.backend.domain.game.model.Room;
 import io.f1.backend.domain.game.websocket.MessageSender;
 import io.f1.backend.domain.quiz.app.QuizService;
-import io.f1.backend.domain.quiz.entity.Quiz;
 
 public record RoundChangeRequest(int round) implements GameSettingChanger {
 
@@ -13,10 +12,9 @@ public boolean change(Room room, QuizService quizService) {
             return false; // 동일하면 무시
         }
 
-        Quiz quiz = quizService.findQuizById(room.getQuizId());
-        int questionSize = quiz.getQuestions().size();
+        Long questionsCount = quizService.getQuestionsCount(room.getQuizId());
 
-        room.changeRound(round, questionSize);
+        room.changeRound(round, questionsCount.intValue());
         return true;
     }
 

backend/src/main/java/io/f1/backend/domain/game/model/GameSetting.java

@@ -1,7 +1,6 @@
 package io.f1.backend.domain.game.model;
 
 import io.f1.backend.domain.game.dto.request.TimeLimit;
-import io.f1.backend.domain.quiz.entity.Quiz;
 import io.f1.backend.global.exception.CustomException;
 import io.f1.backend.global.exception.errorcode.GameErrorCode;
 
@@ -16,9 +15,9 @@ public class GameSetting {
     private Integer round;
     private int timeLimit;
 
-    public void changeQuiz(Quiz quiz) {
-        quizId = quiz.getId();
-        round = quiz.getQuestions().size(); // 라운드를 바꾼 퀴즈의 문제 수로 동기화
+    public void changeQuiz(Long quizId, int questionsCount) {
+        this.quizId = quizId;
+        round = questionsCount; // 라운드를 바꾼 퀴즈의 문제 수로 동기화
     }
 
     public void changeTimeLimit(TimeLimit timeLimit) {

backend/src/main/java/io/f1/backend/domain/game/model/Room.java

@@ -2,7 +2,6 @@
 
 import io.f1.backend.domain.game.dto.request.TimeLimit;
 import io.f1.backend.domain.question.entity.Question;
-import io.f1.backend.domain.quiz.entity.Quiz;
 import io.f1.backend.global.exception.CustomException;
 import io.f1.backend.global.exception.errorcode.RoomErrorCode;
 
@@ -161,8 +160,8 @@ public void resetAllPlayerReadyStates() {
         }
     }
 
-    public void changeQuiz(Quiz quiz) {
-        gameSetting.changeQuiz(quiz);
+    public void changeQuiz(Long quizId, int questionsCount) {
+        gameSetting.changeQuiz(quizId, questionsCount);
     }
 
     public void changeTimeLimit(TimeLimit timeLimit) {

backend/src/main/java/io/f1/backend/domain/quiz/app/QuizService.java

@@ -284,4 +284,9 @@ public Quiz findQuizById(Long quizId) {
                 .findById(quizId)
                 .orElseThrow(() -> new CustomException(QuizErrorCode.QUIZ_NOT_FOUND));
     }
+
+    @Transactional(readOnly = true)
+    public Long getQuestionsCount(Long quizId) {
+        return quizRepository.countQuestionsByQuizId(quizId);
+    }
 }

backend/src/main/java/io/f1/backend/domain/quiz/dao/QuizRepository.java

@@ -21,6 +21,9 @@ public interface QuizRepository extends JpaRepository<Quiz, Long> {
     @Query("SELECT q FROM Quiz q LEFT JOIN FETCH q.questions WHERE q.id = :quizId")
     Optional<Quiz> findQuizWithQuestionsById(Long quizId);
 
+    @Query("SELECT COUNT(qst) FROM Quiz q JOIN q.questions qst WHERE q.id = :quizId")
+    Long countQuestionsByQuizId(Long quizId);
+
     @Query(
 """
     SELECT new io.f1.backend.domain.quiz.dto.QuizMinData (q.id, COUNT(qs.id))