JPA Sequence Key 생성 전략

0. 들어가면서

비즈니스에 따라 기본 키(PK, Primary Key) 값을 애플리케이션에서 직접 지정하는 것이 아니라, 키 값이 자동으로 생성되도록 만들고 이를 사용하는 경우가 있다. JPA는 기본 키 자동 발급을 위한 기능과 몇 가지 전략을 제공하는데, 이번 포스트에선 전략 별로 어떤 차이점이 있는지 정리해보았다.

1. GenerationType.IDENTITY 전략

기본 키 생성을 데이터베이스에 위임한다.

1.1. 테이블 생성

기본 키 생성을 데이터베이스에 위임했기 때문에 테이블을 생성하는 DDL(database define language) 쿼리에 자동 키 발급에 대한 내용이 필요하다. 데이터베이스 벤더에 따라 다르게 작성한다.

H2 데이터베이스 테이블 생성

• generated by default as identity 키워드 - H2 데이터베이스에서 기본 키 자동 발급을 위해 추가된다.

create table identity_entity (
    id bigint generated by default as identity,
    primary key (id)
)

1.2. JPA 지연 쓰기 불가

IDENTITY 전략은 영속성 컨텍스트(persistence context)의 장점 중 하나인 지연 쓰기가 불가능하다. IDENTITY 전략을 사용하면 기본 키 값은 실제 데이터베이스에 데이터를 저장한 이후에 확인할 수 있다. 영속성 컨텍스트는 엔티티(entity)를 1차 캐싱에 저장하기 위해서 기본 키 필드(@Id 애너테이션이 붙은 필드)에 값이 필요하기 때문에 save 메서드 수행 시 insert 쿼리를 매번 flush한다.

1.3. 예시 코드

1.3.1. IdentityEntity 클래스

• @GeneratedValue 애너테이션의 생성 전략을 GenerationType.IDENTITY으로 지정한다.

package blog.in.action.identity;

import lombok.Getter;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Getter
@Entity
public class IdentityEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
}

1.3.2. IdentityTests 클래스

• 반복문을 통해 데이터를 추가를 3회 수행한다.
• 데이터를 조회하여 발급된 기본 키 값을 확인한다.

package blog.in.action.identity;

import lombok.extern.log4j.Log4j2;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;

import java.util.List;

@Log4j2
@DataJpaTest
public class IdentityTests {

    @Autowired
    IdentityRepository repository;

    @Test
    void test() {

        log.info("추가");
        for (int index = 0; index < 3; index++) {
            log.info("before save");
            repository.save(new IdentityEntity());
            log.info("after save");
        }

        log.info("조회");
        List<IdentityEntity> entities = repository.findAll();
        for (IdentityEntity entity : entities) {
            log.info(entity.getId());
        }
    }
}

1.4. 테스트 결과 로그 확인

테스트 수행 로그를 통해 동작 과정을 살펴본다.

• JpaRepository의 save 메서드 수행 시 매번 insert 쿼리가 수행된다.
• insert 쿼리 수행 시 id에 null 값을 삽입하지만, 조회 시 값이 있음을 확인할 수 있다.

2022-06-19 05:36:29.148  INFO 32296 --- [           main] o.s.t.c.transaction.TransactionContext   : Began transaction (1) for test context [DefaultTestContext@2a640157 testClass = IdentityTests, testInstance = blog.in.action.identity.IdentityTests@5f9678e1, testMethod = test@IdentityTests, testException = [null], mergedContextConfiguration = [MergedContextConfiguration@52851b44 testClass = IdentityTests, locations = '{}', classes = '{class blog.in.action.ActionInBlogApplication}', contextInitializerClasses = '[]', activeProfiles = '{}', propertySourceLocations = '{}', propertySourceProperties = '{org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTestContextBootstrapper=true}', contextCustomizers = set[[ImportsContextCustomizer@584f54e6 key = [org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration, org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration, org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration, org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration, org.springframework.boot.autoconfigure.sql.init.SqlInitializationAutoConfiguration, org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration, org.springframework.boot.test.autoconfigure.jdbc.TestDatabaseAutoConfiguration, org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManagerAutoConfiguration]], org.springframework.boot.test.context.filter.ExcludeFilterContextCustomizer@74a6f9c1, org.springframework.boot.test.json.DuplicateJsonObjectContextCustomizerFactory$DuplicateJsonObjectContextCustomizer@63611043, org.springframework.boot.test.mock.mockito.MockitoContextCustomizer@0, org.springframework.boot.test.autoconfigure.OverrideAutoConfigurationContextCustomizerFactory$DisableAutoConfigurationContextCustomizer@51549490, org.springframework.boot.test.autoconfigure.actuate.metrics.MetricsExportContextCustomizerFactory$DisableMetricExportContextCustomizer@7daa0fbd, org.springframework.boot.test.autoconfigure.filter.TypeExcludeFiltersContextCustomizer@351584c0, org.springframework.boot.test.autoconfigure.properties.PropertyMappingContextCustomizer@92765d80, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverContextCustomizerFactory$Customizer@2796aeae, org.springframework.boot.test.context.SpringBootTestArgs@1, org.springframework.boot.test.context.SpringBootTestWebEnvironment@0], contextLoader = 'org.springframework.boot.test.context.SpringBootContextLoader', parent = [null]], attributes = map['org.springframework.test.context.event.ApplicationEventsTestExecutionListener.recordApplicationEvents' -> false]]; transaction manager [org.springframework.orm.jpa.JpaTransactionManager@76dc36e5]; rollback [true]
2022-06-19 05:36:29.236  INFO 32296 --- [           main] blog.in.action.identity.IdentityTests    : 추가
2022-06-19 05:36:29.237  INFO 32296 --- [           main] blog.in.action.identity.IdentityTests    : before save
Hibernate: 
    insert 
    into
        identity_entity
        (id) 
    values
        (null)
2022-06-19 05:36:29.266  INFO 32296 --- [           main] blog.in.action.identity.IdentityTests    : after save
2022-06-19 05:36:29.266  INFO 32296 --- [           main] blog.in.action.identity.IdentityTests    : before save
Hibernate: 
    insert 
    into
        identity_entity
        (id) 
    values
        (null)
2022-06-19 05:36:29.266  INFO 32296 --- [           main] blog.in.action.identity.IdentityTests    : after save
2022-06-19 05:36:29.267  INFO 32296 --- [           main] blog.in.action.identity.IdentityTests    : before save
Hibernate: 
    insert 
    into
        identity_entity
        (id) 
    values
        (null)
2022-06-19 05:36:29.267  INFO 32296 --- [           main] blog.in.action.identity.IdentityTests    : after save
2022-06-19 05:36:29.267  INFO 32296 --- [           main] blog.in.action.identity.IdentityTests    : 조회
Hibernate: 
    select
        identityen0_.id as id1_0_ 
    from
        identity_entity identityen0_
2022-06-19 05:36:29.396  INFO 32296 --- [           main] blog.in.action.identity.IdentityTests    : 1
2022-06-19 05:36:29.396  INFO 32296 --- [           main] blog.in.action.identity.IdentityTests    : 2
2022-06-19 05:36:29.396  INFO 32296 --- [           main] blog.in.action.identity.IdentityTests    : 3
2022-06-19 05:36:29.402  INFO 32296 --- [           main] o.s.t.c.transaction.TransactionContext   : Rolled back transaction for test: [DefaultTestContext@2a640157 testClass = IdentityTests, testInstance = blog.in.action.identity.IdentityTests@5f9678e1, testMethod = test@IdentityTests, testException = [null], mergedContextConfiguration = [MergedContextConfiguration@52851b44 testClass = IdentityTests, locations = '{}', classes = '{class blog.in.action.ActionInBlogApplication}', contextInitializerClasses = '[]', activeProfiles = '{}', propertySourceLocations = '{}', propertySourceProperties = '{org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTestContextBootstrapper=true}', contextCustomizers = set[[ImportsContextCustomizer@584f54e6 key = [org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration, org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration, org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration, org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration, org.springframework.boot.autoconfigure.sql.init.SqlInitializationAutoConfiguration, org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration, org.springframework.boot.test.autoconfigure.jdbc.TestDatabaseAutoConfiguration, org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManagerAutoConfiguration]], org.springframework.boot.test.context.filter.ExcludeFilterContextCustomizer@74a6f9c1, org.springframework.boot.test.json.DuplicateJsonObjectContextCustomizerFactory$DuplicateJsonObjectContextCustomizer@63611043, org.springframework.boot.test.mock.mockito.MockitoContextCustomizer@0, org.springframework.boot.test.autoconfigure.OverrideAutoConfigurationContextCustomizerFactory$DisableAutoConfigurationContextCustomizer@51549490, org.springframework.boot.test.autoconfigure.actuate.metrics.MetricsExportContextCustomizerFactory$DisableMetricExportContextCustomizer@7daa0fbd, org.springframework.boot.test.autoconfigure.filter.TypeExcludeFiltersContextCustomizer@351584c0, org.springframework.boot.test.autoconfigure.properties.PropertyMappingContextCustomizer@92765d80, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverContextCustomizerFactory$Customizer@2796aeae, org.springframework.boot.test.context.SpringBootTestArgs@1, org.springframework.boot.test.context.SpringBootTestWebEnvironment@0], contextLoader = 'org.springframework.boot.test.context.SpringBootContextLoader', parent = [null]], attributes = map['org.springframework.test.context.event.ApplicationEventsTestExecutionListener.recordApplicationEvents' -> false]]

2. GenerationType.SEQUENCE 전략

데이터베이스의 시퀀스 객체(sequence object)를 이용하여 유일한 값을 순서대로 생성합니다.

2.1. 시퀀스 객체와 테이블 생성

GenerationType.SEQUENCE 전략은 데이터베이스에 미리 만들어진 시퀀스 객체를 사용한다. 시퀀스 객체를 만드는 방법과 사용하는 방법은 데이터베이스 벤더마다 다르다.

H2 데이터베이스 시퀀스 객체 생성

• my_seq라는 이름의 시퀀스 객체를 생성한다.
• 최초 값은 1에서 시작하고, 사용할 때마다 1씩 증가한다.

create sequence my_seq start with 1 increment by 1

2.2. 예시 코드

2.2.1. SequenceEntity 클래스

• @GeneratedValue 애너테이션
  • 생성 전략을 GenerationType.SEQUENCE으로 지정한다.
  • 기본 키 생성자를 SEQ_GENERATOR으로 지정한다.
• @SequenceGenerator 애너테이션
  • name - 기본 키 생성자 이름은 SEQ_GENERATOR이다.
  • sequenceName - SEQ_GENERATOR가 사용할 데이터베이스의 시퀀스 객체는 MY_SEQ이다.
  • allocationSize - 시퀀스 객체 호출 시 증가하는 값은 1로 지정한다.

package blog.in.action.sequence;

import lombok.Getter;

import javax.persistence.*;

@Getter
@SequenceGenerator(
        name = "SEQ_GENERATOR",
        sequenceName = "MY_SEQ",
        allocationSize = 1
)
@Entity
public class SequenceEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQ_GENERATOR")
    private Long id;
}

2.2.2. SequenceTests 클래스

• 반복문을 통해 데이터를 추가를 3회 수행한다.
• 데이터를 조회하여 발급된 기본 키 값을 확인한다.

package blog.in.action.sequence;

import lombok.extern.log4j.Log4j2;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;

import java.util.List;

@Log4j2
@DataJpaTest
public class SequenceTests {

    @Autowired
    SequenceRepository repository;

    @Test
    void test() {

        log.info("추가");
        for (int index = 0; index < 3; index++) {
            log.info("before save");
            repository.save(new SequenceEntity());
            log.info("after save");
        }

        log.info("조회");
        List<SequenceEntity> entities = repository.findAll();
        for (SequenceEntity entity : entities) {
            log.info(entity.getId());
        }
    }
}

2.3. 테스트 결과 로그 확인

테스트 수행 로그를 통해 동작 과정을 살펴본다.

• JpaRepository의 save 메서드 수행 시 매번 시퀀스 값을 발급받는다.
  • call next value for my_seq - H2 데이터베이스에서 시퀀스 키를 발급받는 방법이다.
• 데이터를 조회하는 select 쿼리 수행 전에 JPA 지연 쓰기를 수행하기 때문에 insert 쿼리가 3회 수행된다.
  • insert 쿼리 수행 시 id에 발급받은 시퀀스 값을 사용한다.

2022-06-19 06:46:54.910  INFO 54837 --- [           main] o.s.t.c.transaction.TransactionContext   : Began transaction (1) for test context [DefaultTestContext@2dca0d64 testClass = SequenceTests, testInstance = blog.in.action.sequence.SequenceTests@112f364d, testMethod = test@SequenceTests, testException = [null], mergedContextConfiguration = [MergedContextConfiguration@f80945f testClass = SequenceTests, locations = '{}', classes = '{class blog.in.action.ActionInBlogApplication}', contextInitializerClasses = '[]', activeProfiles = '{}', propertySourceLocations = '{}', propertySourceProperties = '{org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTestContextBootstrapper=true}', contextCustomizers = set[[ImportsContextCustomizer@ff684e1 key = [org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration, org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration, org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration, org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration, org.springframework.boot.autoconfigure.sql.init.SqlInitializationAutoConfiguration, org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration, org.springframework.boot.test.autoconfigure.jdbc.TestDatabaseAutoConfiguration, org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManagerAutoConfiguration]], org.springframework.boot.test.context.filter.ExcludeFilterContextCustomizer@74a6f9c1, org.springframework.boot.test.json.DuplicateJsonObjectContextCustomizerFactory$DuplicateJsonObjectContextCustomizer@63611043, org.springframework.boot.test.mock.mockito.MockitoContextCustomizer@0, org.springframework.boot.test.autoconfigure.OverrideAutoConfigurationContextCustomizerFactory$DisableAutoConfigurationContextCustomizer@51549490, org.springframework.boot.test.autoconfigure.actuate.metrics.MetricsExportContextCustomizerFactory$DisableMetricExportContextCustomizer@7daa0fbd, org.springframework.boot.test.autoconfigure.filter.TypeExcludeFiltersContextCustomizer@351584c0, org.springframework.boot.test.autoconfigure.properties.PropertyMappingContextCustomizer@92765d80, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverContextCustomizerFactory$Customizer@2796aeae, org.springframework.boot.test.context.SpringBootTestArgs@1, org.springframework.boot.test.context.SpringBootTestWebEnvironment@0], contextLoader = 'org.springframework.boot.test.context.SpringBootContextLoader', parent = [null]], attributes = map['org.springframework.test.context.event.ApplicationEventsTestExecutionListener.recordApplicationEvents' -> false]]; transaction manager [org.springframework.orm.jpa.JpaTransactionManager@3ee258]; rollback [true]
2022-06-19 06:46:54.990  INFO 54837 --- [           main] blog.in.action.sequence.SequenceTests    : 추가
2022-06-19 06:46:54.990  INFO 54837 --- [           main] blog.in.action.sequence.SequenceTests    : before save
Hibernate: 
    call next value for my_seq
2022-06-19 06:46:55.018  INFO 54837 --- [           main] blog.in.action.sequence.SequenceTests    : after save
2022-06-19 06:46:55.019  INFO 54837 --- [           main] blog.in.action.sequence.SequenceTests    : before save
Hibernate: 
    call next value for my_seq
2022-06-19 06:46:55.019  INFO 54837 --- [           main] blog.in.action.sequence.SequenceTests    : after save
2022-06-19 06:46:55.019  INFO 54837 --- [           main] blog.in.action.sequence.SequenceTests    : before save
Hibernate: 
    call next value for my_seq
2022-06-19 06:46:55.020  INFO 54837 --- [           main] blog.in.action.sequence.SequenceTests    : after save
2022-06-19 06:46:55.020  INFO 54837 --- [           main] blog.in.action.sequence.SequenceTests    : 조회
Hibernate: 
    insert 
    into
        sequence_entity
        (id) 
    values
        (?)
Hibernate: 
    insert 
    into
        sequence_entity
        (id) 
    values
        (?)
Hibernate: 
    insert 
    into
        sequence_entity
        (id) 
    values
        (?)
Hibernate: 
    select
        sequenceen0_.id as id1_1_ 
    from
        sequence_entity sequenceen0_
2022-06-19 06:46:55.135  INFO 54837 --- [           main] blog.in.action.sequence.SequenceTests    : 1
2022-06-19 06:46:55.136  INFO 54837 --- [           main] blog.in.action.sequence.SequenceTests    : 2
2022-06-19 06:46:55.136  INFO 54837 --- [           main] blog.in.action.sequence.SequenceTests    : 3
2022-06-19 06:46:55.143  INFO 54837 --- [           main] o.s.t.c.transaction.TransactionContext   : Rolled back transaction for test: [DefaultTestContext@2dca0d64 testClass = SequenceTests, testInstance = blog.in.action.sequence.SequenceTests@112f364d, testMethod = test@SequenceTests, testException = [null], mergedContextConfiguration = [MergedContextConfiguration@f80945f testClass = SequenceTests, locations = '{}', classes = '{class blog.in.action.ActionInBlogApplication}', contextInitializerClasses = '[]', activeProfiles = '{}', propertySourceLocations = '{}', propertySourceProperties = '{org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTestContextBootstrapper=true}', contextCustomizers = set[[ImportsContextCustomizer@ff684e1 key = [org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration, org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration, org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration, org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration, org.springframework.boot.autoconfigure.sql.init.SqlInitializationAutoConfiguration, org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration, org.springframework.boot.test.autoconfigure.jdbc.TestDatabaseAutoConfiguration, org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManagerAutoConfiguration]], org.springframework.boot.test.context.filter.ExcludeFilterContextCustomizer@74a6f9c1, org.springframework.boot.test.json.DuplicateJsonObjectContextCustomizerFactory$DuplicateJsonObjectContextCustomizer@63611043, org.springframework.boot.test.mock.mockito.MockitoContextCustomizer@0, org.springframework.boot.test.autoconfigure.OverrideAutoConfigurationContextCustomizerFactory$DisableAutoConfigurationContextCustomizer@51549490, org.springframework.boot.test.autoconfigure.actuate.metrics.MetricsExportContextCustomizerFactory$DisableMetricExportContextCustomizer@7daa0fbd, org.springframework.boot.test.autoconfigure.filter.TypeExcludeFiltersContextCustomizer@351584c0, org.springframework.boot.test.autoconfigure.properties.PropertyMappingContextCustomizer@92765d80, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverContextCustomizerFactory$Customizer@2796aeae, org.springframework.boot.test.context.SpringBootTestArgs@1, org.springframework.boot.test.context.SpringBootTestWebEnvironment@0], contextLoader = 'org.springframework.boot.test.context.SpringBootContextLoader', parent = [null]], attributes = map['org.springframework.test.context.event.ApplicationEventsTestExecutionListener.recordApplicationEvents' -> false]]

3. GenerationType.TABLE 전략

키 생성 전용 테이블을 하나 만들고 여기에 이름과 값으로 사용할 컬럼을 만들어 데이터베이스 시퀀스를 흉내내는 전략입니다.

3.1. 테이블 생성

시퀀스 값을 발급하기 위한 테이블을 별도로 만들었기 때문에 데이터베이스 벤더에 의존적이지 않다. 모든 데이터베이스 벤더에서 동일하게 사용할 수 있지만, 시퀀스 테이블 생성 및 초기화 작업이 반드시 선행되어야 한다.

H2 데이터베이스 시퀀스 테이블 생성 및 초기화

• 시퀀스 이름(sequence_name)과 시퀀스 값(next_val)을 가지는 테이블을 만든다.
  • 시퀀스 이름은 별도로 지정하지 않는 경우 디폴트 값으로 엔티티 이름을 사용한다.
• 테이블을 만든 후에 사용할 시퀀스 이름과 초기 값을 insert한다.

create table seq_table (
   sequence_name varchar(255) not null,
    next_val bigint,
    primary key (sequence_name)
)

insert into seq_table(sequence_name, next_val) values ('table_entity', 0)

3.2. 예시 코드

3.2.1. TableEntity 클래스

• @GeneratedValue 애너테이션
  • 생성 전략을 GenerationType.SEQUENCE으로 지정한다.
  • 기본 키 생성자를 TABLE_SEQ_GENERATOR으로 지정한다.
• @TableGenerator 애너테이션
  • name - 기본 키 생성자 이름은 TABLE_SEQ_GENERATOR이다.
  • table - TABLE_SEQ_GENERATOR가 사용할 데이터베이스의 테이블은 SEQ_TABLE이다.
  • allocationSize - 시퀀스 테이블 사용 시 증가하는 값은 1로 지정한다.

package blog.in.action.table;

import lombok.Getter;

import javax.persistence.*;

@Getter
@TableGenerator(
        name = "TABLE_SEQ_GENERATOR",
        table = "SEQ_TABLE",
        allocationSize = 1
)
@Entity
public class TableEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.TABLE, generator = "TABLE_SEQ_GENERATOR")
    private Long id;
}

3.2.2. TableTests 클래스

• 반복문을 통해 데이터를 추가를 3회 수행한다.
• 데이터를 조회하여 발급된 기본 키 값을 확인한다.

package blog.in.action.table;

import lombok.extern.log4j.Log4j2;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;

import java.util.List;

@Log4j2
@DataJpaTest
public class TableTests {

    @Autowired
    TableRepository repository;

    @Test
    void test() {

        log.info("추가");
        for (int index = 0; index < 3; index++) {
            log.info("before save");
            repository.save(new TableEntity());
            log.info("after save");
        }

        log.info("조회");
        List<TableEntity> entities = repository.findAll();
        for (TableEntity entity : entities) {
            log.info(entity.getId());
        }
    }
}

3.3. 테스트 결과 로그 확인

테스트 수행 로그를 통해 동작 과정을 살펴본다.

• JpaRepository의 save 메서드 수행 시 매번 시퀀스 값을 발급받는다.
  • 시퀀스 값 발급을 위해 select, update 2회 쿼리가 수행된다.
  • select 쿼리 - seq_table 테이블로부터 엔티티에 해당되는 시퀀스 값을 조회한다. for update 키워드로 해당 시퀀스 데이터를 조회하면서 데이터 락(lock)을 수행한다.
  • update 쿼리 - seq_table 테이블에 해당 엔티티가 다음으로 사용할 시퀀스 값을 update한다.
• 데이터를 조회하는 select 쿼리 수행 전에 JPA 지연 쓰기를 수행하기 때문에 insert 쿼리가 3회 수행된다.
  • insert 쿼리 수행 시 id에 발급받은 시퀀스 값을 사용한다.

2022-06-19 07:17:43.340  INFO 64356 --- [           main] o.s.t.c.transaction.TransactionContext   : Began transaction (1) for test context [DefaultTestContext@74bada02 testClass = TableTests, testInstance = blog.in.action.table.TableTests@31d0e481, testMethod = test@TableTests, testException = [null], mergedContextConfiguration = [MergedContextConfiguration@525575 testClass = TableTests, locations = '{}', classes = '{class blog.in.action.ActionInBlogApplication}', contextInitializerClasses = '[]', activeProfiles = '{}', propertySourceLocations = '{}', propertySourceProperties = '{org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTestContextBootstrapper=true}', contextCustomizers = set[[ImportsContextCustomizer@46dffdc3 key = [org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration, org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration, org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration, org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration, org.springframework.boot.autoconfigure.sql.init.SqlInitializationAutoConfiguration, org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration, org.springframework.boot.test.autoconfigure.jdbc.TestDatabaseAutoConfiguration, org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManagerAutoConfiguration]], org.springframework.boot.test.context.filter.ExcludeFilterContextCustomizer@135606db, org.springframework.boot.test.json.DuplicateJsonObjectContextCustomizerFactory$DuplicateJsonObjectContextCustomizer@4f74980d, org.springframework.boot.test.mock.mockito.MockitoContextCustomizer@0, org.springframework.boot.test.autoconfigure.OverrideAutoConfigurationContextCustomizerFactory$DisableAutoConfigurationContextCustomizer@616ac46a, org.springframework.boot.test.autoconfigure.actuate.metrics.MetricsExportContextCustomizerFactory$DisableMetricExportContextCustomizer@6337c201, org.springframework.boot.test.autoconfigure.filter.TypeExcludeFiltersContextCustomizer@351584c0, org.springframework.boot.test.autoconfigure.properties.PropertyMappingContextCustomizer@92765d80, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverContextCustomizerFactory$Customizer@2ce6c6ec, org.springframework.boot.test.context.SpringBootTestArgs@1, org.springframework.boot.test.context.SpringBootTestWebEnvironment@0], contextLoader = 'org.springframework.boot.test.context.SpringBootContextLoader', parent = [null]], attributes = map['org.springframework.test.context.event.ApplicationEventsTestExecutionListener.recordApplicationEvents' -> false]]; transaction manager [org.springframework.orm.jpa.JpaTransactionManager@29699283]; rollback [true]
2022-06-19 07:17:43.427  INFO 64356 --- [           main] blog.in.action.table.TableTests          : 추가
2022-06-19 07:17:43.428  INFO 64356 --- [           main] blog.in.action.table.TableTests          : before save
Hibernate: 
    select
        tbl.next_val 
    from
        seq_table tbl 
    where
        tbl.sequence_name=? for update
            
Hibernate: 
    update
        seq_table 
    set
        next_val=?  
    where
        next_val=? 
        and sequence_name=?
2022-06-19 07:17:43.461  INFO 64356 --- [           main] blog.in.action.table.TableTests          : after save
2022-06-19 07:17:43.461  INFO 64356 --- [           main] blog.in.action.table.TableTests          : before save
Hibernate: 
    select
        tbl.next_val 
    from
        seq_table tbl 
    where
        tbl.sequence_name=? for update
            
Hibernate: 
    update
        seq_table 
    set
        next_val=?  
    where
        next_val=? 
        and sequence_name=?
2022-06-19 07:17:43.463  INFO 64356 --- [           main] blog.in.action.table.TableTests          : after save
2022-06-19 07:17:43.463  INFO 64356 --- [           main] blog.in.action.table.TableTests          : before save
Hibernate: 
    select
        tbl.next_val 
    from
        seq_table tbl 
    where
        tbl.sequence_name=? for update
            
Hibernate: 
    update
        seq_table 
    set
        next_val=?  
    where
        next_val=? 
        and sequence_name=?
2022-06-19 07:17:43.465  INFO 64356 --- [           main] blog.in.action.table.TableTests          : after save
2022-06-19 07:17:43.465  INFO 64356 --- [           main] blog.in.action.table.TableTests          : 조회
Hibernate: 
    insert 
    into
        table_entity
        (id) 
    values
        (?)
Hibernate: 
    insert 
    into
        table_entity
        (id) 
    values
        (?)
Hibernate: 
    insert 
    into
        table_entity
        (id) 
    values
        (?)
Hibernate: 
    select
        tableentit0_.id as id1_2_ 
    from
        table_entity tableentit0_
2022-06-19 07:17:43.589  INFO 64356 --- [           main] blog.in.action.table.TableTests          : 1
2022-06-19 07:17:43.589  INFO 64356 --- [           main] blog.in.action.table.TableTests          : 2
2022-06-19 07:17:43.589  INFO 64356 --- [           main] blog.in.action.table.TableTests          : 3
2022-06-19 07:17:43.597  INFO 64356 --- [           main] o.s.t.c.transaction.TransactionContext   : Rolled back transaction for test: [DefaultTestContext@74bada02 testClass = TableTests, testInstance = blog.in.action.table.TableTests@31d0e481, testMethod = test@TableTests, testException = [null], mergedContextConfiguration = [MergedContextConfiguration@525575 testClass = TableTests, locations = '{}', classes = '{class blog.in.action.ActionInBlogApplication}', contextInitializerClasses = '[]', activeProfiles = '{}', propertySourceLocations = '{}', propertySourceProperties = '{org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTestContextBootstrapper=true}', contextCustomizers = set[[ImportsContextCustomizer@46dffdc3 key = [org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration, org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration, org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration, org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration, org.springframework.boot.autoconfigure.sql.init.SqlInitializationAutoConfiguration, org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration, org.springframework.boot.test.autoconfigure.jdbc.TestDatabaseAutoConfiguration, org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManagerAutoConfiguration]], org.springframework.boot.test.context.filter.ExcludeFilterContextCustomizer@135606db, org.springframework.boot.test.json.DuplicateJsonObjectContextCustomizerFactory$DuplicateJsonObjectContextCustomizer@4f74980d, org.springframework.boot.test.mock.mockito.MockitoContextCustomizer@0, org.springframework.boot.test.autoconfigure.OverrideAutoConfigurationContextCustomizerFactory$DisableAutoConfigurationContextCustomizer@616ac46a, org.springframework.boot.test.autoconfigure.actuate.metrics.MetricsExportContextCustomizerFactory$DisableMetricExportContextCustomizer@6337c201, org.springframework.boot.test.autoconfigure.filter.TypeExcludeFiltersContextCustomizer@351584c0, org.springframework.boot.test.autoconfigure.properties.PropertyMappingContextCustomizer@92765d80, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverContextCustomizerFactory$Customizer@2ce6c6ec, org.springframework.boot.test.context.SpringBootTestArgs@1, org.springframework.boot.test.context.SpringBootTestWebEnvironment@0], contextLoader = 'org.springframework.boot.test.context.SpringBootContextLoader', parent = [null]], attributes = map['org.springframework.test.context.event.ApplicationEventsTestExecutionListener.recordApplicationEvents' -> false]]

4. GenerationType.AUTO 전략

데이터베이스에 따라 INDENTITY, SEQUENCE, TABLE 전략 중 하나를 자동으로 선택한다.

키 생성 전략이 정해지지 않은 개발 초기 단계나 프로토타입 개발 시 편리하게 사용할 수 있다. 데이터베이스 벤더마다 다른 전략을 선택하기 때문에 SEQUENCE, TABLE 전략이 선택된다면 미리 선행 작업이 필요할 수 있다.

H2 데이터베이스 AUTO 전략 사용 시 시퀀스 객체 생성

• H2 데이터베이스는 SEQUENCE 전략을 사용한다.

create sequence hibernate_sequence start with 1 increment by 1

TEST CODE REPOSITORY

• blog-in-action / jpa-sequence-key-generate-strategyGitHub · 예제 코드

REFERENCE

• https://xzio.tistory.com/1446
• https://newwisdom.tistory.com/90