refactor: select in을 통해 n+1해소 #587
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poi1649
requested changes
Oct 27, 2023
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| Given "jinwoo"가 제목-"자스", 정원-"6"명, 최소 주차-"7"주, 주당 진행 횟수-"3"회, 소개-"스터디소개1"로 스터디를 개설한다. | ||
| Given "jinwoo"가 제목-"자스", 정원-"6"명, 최소 주차-"7"주, 주당 진행 횟수-"3"회, 소개-"스터디소개1"로 스터디를 개설한다. |
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| List<Study> studies = queryFactory.selectFrom(study) | ||
| List<Long> studyIds = queryFactory.select(study.id) | ||
| .from(study) | ||
| .where(searchEq(search), statusEq(status)) | ||
| .offset(page.getOffset()) | ||
| .limit(page.getPageSize()) | ||
| .orderBy(orderSpecifier(page)) | ||
| .fetch(); | ||
|
|
||
| List<Study> studies = queryFactory.selectFrom(study) | ||
| .join(study.studyMembers, studyMember).fetchJoin() | ||
| .join(studyMember.member, member).fetchJoin() | ||
| .where(study.id.in(studyIds)) | ||
| .orderBy(orderSpecifier(page)) | ||
| .fetch(); |
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궁금한 점이 두 가지 있습니다.
- 실제로 이렇게 쿼리를 두 번 날리는 것이 평균적으로 얼마나 더 빠른지
- 기존의 n+1 이 어떤 과정에서 일어나는지
실제 실행기록을 첨부해주실 수 있을까요?
yujamint
approved these changes
Nov 1, 2023
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😋 작업한 내용
fetch join을 할 경우 페이징이 똑바로 되지 않음
조건에 해당하는 study id들을 조회하는 쿼리를 날린 후에 where in 절로 fetch join 후 조회하는 쿼리를 한번 더 날린다
총 2회로 n+1없이 페이징 조회 가능
🙏 PR Point
👍 관련 이슈