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refactor: select in을 통해 n+1해소 #587

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refactor: select in을 통해 n+1해소 #587

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10 changes: 9 additions & 1 deletion .../src/main/java/com/yigongil/backend/domain/study/studyquery/StudyQueryRepositoryImpl.java
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
package com.yigongil.backend.domain.study.studyquery;

import static com.yigongil.backend.domain.member.QMember.member;
import static com.yigongil.backend.domain.study.QStudy.study;
import static com.yigongil.backend.domain.studymember.QStudyMember.studyMember;

Expand Down Expand Up @@ -32,13 +33,20 @@ public StudyQueryRepositoryImpl(JPAQueryFactory queryFactory) {
@Override
public Slice<Study> findStudiesByConditions(String search, ProcessingStatus status, Pageable page) {

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();
Comment on lines -35 to +49
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궁금한 점이 두 가지 있습니다.

  1. 실제로 이렇게 쿼리를 두 번 날리는 것이 평균적으로 얼마나 더 빠른지
  2. 기존의 n+1 이 어떤 과정에서 일어나는지

실제 실행기록을 첨부해주실 수 있을까요?

return new SliceImpl<>(studies);
}

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2 changes: 2 additions & 0 deletions backend/src/test/resources/features/find-study.feature
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Expand Up @@ -29,6 +29,8 @@ Feature: 스터디 목록 조회 기능
Given "jinwoo"가 제목-"자바1", 정원-"6"명, 최소 주차-"7"주, 주당 진행 횟수-"3"회, 소개-"스터디소개1"로 스터디를 개설한다.
Given "jinwoo"가 제목-"자바2", 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.
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.
Comment on lines +32 to +33
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두개가 늘어난 이유는 뭔가요?


When 스터디 목록을 "자바" 검색어와 조회한다.

Expand Down