mybatis에서 N+1 문제 해결
바로 직전처럼 Mybatis를 사용해서 oneToMany 상황에 설정해서 쓸수 있는 방법이 있습니다.
하지만 첫번째 상황은 N+1 문제에 직면하게 됩니다. 이부분을 조인 쿼리를 통해서 해결 할수 있습니다.
먼저 mybatis xml 설정은
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| <?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.github.sejoung.test.sample.mapper.MemberMapper">
<resultMap id="MemberDTOJoinResult" type="com.github.sejoung.test.sample.dto.MemberDTO">
<id property="memberId" column="memberId"/>
<result property="name" column="name"/>
<result property="createDate" column="createDate"/>
<collection property="details" column="memberId"
ofType="com.github.sejoung.test.sample.dto.MemberDetailDTO">
<id property="memberDetailId" column="memberDetailId"/>
<result property="type" column="type"/>
<result property="description" column="description"/>
</collection>
</resultMap>
<select id="selectMemberListJoinXML" resultMap="MemberDTOJoinResult">
select M.member_id as memberId, M.name, M.create_dt as createDate, MD.member_detail_id as memberDetailId, MD.type, MD.description from MEMBER M inner join MEMBER_DETAIL MD on M.member_id = MD.member_id
</select>
</mapper>
|
위처럼 조인 쿼리를 사용하면 한번에 쿼리에 필요한 데이터를 조회 할수 있습니다.
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|
@Transactional
@DisplayName("XML 설정 조인 쿼리")
@Test
void selectMemberListJoinXML() {
saveData();
List<MemberDTO> memberList = memberMapper.selectMemberListJoinXML();
log.debug("memberList {}", memberList);
Assertions.assertThat(memberList.size()).isOne();
Assertions.assertThat(memberList.get(0).getDetails().size()).isEqualTo(2);
}
private void saveData() {
var member = Member.builder().name("완구").createDate(LocalDateTime.now()).build();
entityManager.persist(member);
entityManager
.persist(MemberDetail.builder().description("레고").type("장난감").member(member).build());
entityManager
.persist(
MemberDetail.builder().description("플레이모빌").type("장난감").member(member).build());
entityManager.flush();
}
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위처럼 테스트 코드를 통해서 확인 해볼수 있었습니다.
참조
