refactor: 채팅방 조회 성능 개선

src/main/java/gg/agit/konect/domain/chat/dto/AdminChatRoomProjection.java

@@ -0,0 +1,18 @@
+package gg.agit.konect.domain.chat.dto;
+
+import java.time.LocalDateTime;
+
+/**
+ * 관리자용 1:1 채팅방 목록 조회를 위한 Projection DTO
+ * 필드 순서와 타입이 JPQL SELECT 절과 정확히 일치해야 합니다.
+ */
+public record AdminChatRoomProjection(
+    Integer roomId,
+    String lastMessage,
+    LocalDateTime lastSentAt,
+    Integer nonAdminUserId,
+    String nonAdminUserName,
+    String nonAdminImageUrl,
+    Long unreadCount
+) {
+}

src/main/java/gg/agit/konect/domain/chat/repository/ChatRoomRepository.java

@@ -7,6 +7,7 @@
 import org.springframework.data.repository.Repository;
 import org.springframework.data.repository.query.Param;
 
+import gg.agit.konect.domain.chat.dto.AdminChatRoomProjection;
 import gg.agit.konect.domain.chat.model.ChatRoom;
 import gg.agit.konect.domain.user.enums.UserRole;
 
@@ -114,4 +115,49 @@ List<ChatRoom> findAllSystemAdminDirectRooms(
         @Param("systemAdminId") Integer systemAdminId,
         @Param("adminRole") UserRole adminRole
     );
+
+    /**
+     * 관리자용 1:1 채팅방 목록을 Projection DTO로 최적화 조회
+     * <p>
+     * 사용자가 응답한 채팅방만 필터링하고, 필요한 필드만 한 번에 조회합니다.
+     * 이 메소드는 다음과 같은 최적화를 제공합니다:
+     * <ul>
+     *   <li>ChatRoom 엔티티 전체 로딩 대신 필요한 필드만 Projection</li>
+     *   <li>읽지 않은 메시지 수를 DB에서 직접 계산 (COUNT 서브쿼리)</li>
+     *   <li>상대방 사용자 정보를 JOIN으로 한 번에 조회</li>
+     * </ul>
+     */
+    @Query("""
+        SELECT new gg.agit.konect.domain.chat.dto.AdminChatRoomProjection(
+            cr.id,
+            cr.lastMessageContent,
+            cr.lastMessageSentAt,
+            u.id,
+            u.name,
+            u.imageUrl,
+            COUNT(cm)
+        )
+        FROM ChatRoom cr
+        JOIN ChatRoomMember crm ON crm.id.chatRoomId = cr.id
+        JOIN User u ON u.id = crm.id.userId
+        JOIN ChatRoomMember adminCrm ON adminCrm.id.chatRoomId = cr.id
+            AND adminCrm.id.userId = :systemAdminId
+        LEFT JOIN ChatMessage cm ON cm.chatRoom.id = cr.id
+            AND cm.sender.id <> :systemAdminId
+            AND cm.createdAt > adminCrm.lastReadAt
+        WHERE cr.club IS NULL
+          AND u.role != :adminRole
+          AND EXISTS (
+              SELECT 1 FROM ChatMessage userReply
+              JOIN userReply.sender userSender
+              WHERE userReply.chatRoom.id = cr.id
+                AND userSender.role != :adminRole
+          )
+        GROUP BY cr.id, cr.lastMessageContent, cr.lastMessageSentAt, u.id, u.name, u.imageUrl
+        ORDER BY cr.lastMessageSentAt DESC NULLS LAST, cr.id
+        """)
+    List<AdminChatRoomProjection> findAdminChatRoomsOptimized(
+        @Param("systemAdminId") Integer systemAdminId,
+        @Param("adminRole") UserRole adminRole
+    );
 }

src/main/java/gg/agit/konect/domain/chat/service/ChatService.java

@@ -9,7 +9,6 @@
 import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -30,6 +29,7 @@
 import gg.agit.konect.domain.chat.dto.ChatRoomResponse;
 import gg.agit.konect.domain.chat.dto.ChatRoomSummaryResponse;
 import gg.agit.konect.domain.chat.dto.ChatRoomsSummaryResponse;
+import gg.agit.konect.domain.chat.dto.AdminChatRoomProjection;
 import gg.agit.konect.domain.chat.dto.UnreadMessageCount;
 import gg.agit.konect.domain.chat.enums.ChatType;
 import gg.agit.konect.domain.chat.event.AdminChatReceivedEvent;
@@ -277,59 +277,22 @@ private List<ChatRoomSummaryResponse> getDirectChatRooms(Integer userId) {
     }
 
     private List<ChatRoomSummaryResponse> getAdminDirectChatRooms() {
-        List<ChatRoomSummaryResponse> roomSummaries = new ArrayList<>();
-
-        List<ChatRoom> adminUserRooms = chatRoomRepository.findAllSystemAdminDirectRooms(
+        List<AdminChatRoomProjection> projections = chatRoomRepository.findAdminChatRoomsOptimized(
             SYSTEM_ADMIN_ID, UserRole.ADMIN
         );
-        List<Integer> roomIds = extractChatRoomIds(adminUserRooms);
-        Map<Integer, List<MemberInfo>> roomMemberInfoMap = getRoomMemberInfoMap(adminUserRooms);
-        Map<Integer, Integer> adminUnreadCountMap = getAdminUnreadCountMap(roomIds);
-        Set<Integer> repliedRoomIds = roomIds.isEmpty()
-            ? Set.of()
-            : new HashSet<>(chatMessageRepository.findRoomIdsWithUserReplyByRoomIds(roomIds, UserRole.ADMIN));
-
-        List<Integer> allUserIds = roomMemberInfoMap.values().stream()
-            .flatMap(List::stream)
-            .map(MemberInfo::userId)
-            .distinct()
-            .toList();
-
-        Map<Integer, User> userMap = allUserIds.isEmpty()
-            ? Map.of()
-            : userRepository.findAllByIdIn(allUserIds).stream()
-            .collect(Collectors.toMap(User::getId, user -> user));
 
-        for (ChatRoom chatRoom : adminUserRooms) {
-            List<MemberInfo> memberInfos = roomMemberInfoMap.getOrDefault(chatRoom.getId(), List.of());
-            User nonAdminUser = findNonAdminUserFromMemberInfo(memberInfos, userMap);
-            if (nonAdminUser == null) {
-                continue;
-            }
-            if (!repliedRoomIds.contains(chatRoom.getId())) {
-                continue;
-            }
-
-            roomSummaries.add(new ChatRoomSummaryResponse(
-                chatRoom.getId(),
+        return projections.stream()
+            .map(projection -> new ChatRoomSummaryResponse(
+                projection.roomId(),
                 ChatType.DIRECT,
-                nonAdminUser.getName(),
-                nonAdminUser.getImageUrl(),
-                chatRoom.getLastMessageContent(),
-                chatRoom.getLastMessageSentAt(),
-                adminUnreadCountMap.getOrDefault(chatRoom.getId(), 0),
+                projection.nonAdminUserName(),
+                projection.nonAdminImageUrl(),
+                projection.lastMessage(),
+                projection.lastSentAt(),
+                projection.unreadCount().intValue(),
                 false
-            ));
-        }
-
-        roomSummaries.sort(Comparator
-            .comparing(
-                ChatRoomSummaryResponse::lastSentAt,
-                Comparator.nullsLast(Comparator.reverseOrder())
-            )
-            .thenComparing(ChatRoomSummaryResponse::roomId));
-
-        return roomSummaries;
+            ))
+            .toList();
     }
 
     private ChatMessagePageResponse getDirectChatRoomMessages(

src/main/resources/db/migration/V57__add_chat_admin_query_indexes.sql

@@ -0,0 +1,10 @@
+-- 관리자 1:1 채팅방 조회 쿼리 최적화를 위한 인덱스 추가
+-- findAdminChatRoomsOptimized() 메소드 성능 개선
+
+-- 1. 관리자 응답 여부 확인 및 unread count 계산용
+CREATE INDEX idx_chat_message_room_sender
+    ON chat_message (chat_room_id, sender_id);
+
+-- 2. last_message_sent_at 정렬 최적화
+CREATE INDEX idx_chat_room_last_message
+    ON chat_room (club_id, last_message_sent_at DESC);