Respond to code review feedback on student query performance optimization

[Copilot]

Provided comprehensive analysis of the QueryDSL-based student query refactoring in response to reviewer questions about potential issues, naming improvements, and optimization benefits.

Analysis Provided

Potential Issues Identified:

• Memory overhead from groupBy operations when student count is high
• Inconsistent nullable handling in StudentQueryDto (List<FixedRoomEntity?>? double-nullable pattern)
• Naming ambiguity between findAllByX (returns UserEntity) and findAllInfoByX (returns StudentQueryDto)
• Query inefficiency in findAllInfoByRoomTypeStatusAndRole missing room filter

Method Naming Recommendations:

• Repository: findStudentsByGradeAndClass, findStudentDetailsWithAttendanceByFixedRoom
• Service: getStudentsByFixedRoom, getStudentsByClass
• Response: fromQueryResults, fromQueryResultsWithoutFixedRooms

Performance Improvements Confirmed:

• Eliminates N+1 query problem through single fetch with joins
• Strategic use of innerJoin for required relations, leftJoin for optional
• Type-safe projection via @QueryProjection

// Before: Multiple queries per student
students.forEach { student ->
    student.studentInfo  // Query 1
    student.fixedRooms   // Query 2
    student.attendances  // Query 3
}

// After: Single query with groupBy
queryFactory.from(userEntity)
    .innerJoin(studentInfoEntity)
    .leftJoin(fixedRoomEntity)
    .leftJoin(attendanceEntity)
    .transform(groupBy(userEntity.id).list(...))

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