MultipleBagFetchException 문제 발생
web/JPA

MultipleBagFetchException 문제 발생

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엔티티에 연관되어 있는 다른 테이블의 데이터를 2개 이상 fetch join하려고 시도했다. 

예를 들어보면 아래와 같이 Classes엔티티에 oneToMany관계인 student와 teacher 두개에 엔티티를 fetch join으로 가지고 오고자 했다.

 

Classes.java

package com.wedul.jpa.school;

import lombok.Builder;
import lombok.Getter;
import lombok.NoArgsConstructor;

import javax.persistence.*;
import java.util.List;

@Getter
@NoArgsConstructor
@Entity
@Table
public class Classes {

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

    @OneToMany(mappedBy = "classes")
    private List<Student> students;

    @OneToMany(mappedBy = "classes")
    private List<Teacher> teachers;

    @Builder
    public Classes(List<Student> students, List<Teacher> teachers) {
        this.students = students;
        this.teachers = teachers;
    }

    public void updateStudents(List<Student> students) {
        students.forEach(student -> student.updateClasses(this));
        this.students = students;
    }

    public void updateTeachers(List<Teacher> teachers) {
        teachers.forEach(teacher -> teacher.updateClasses(this));
        this.teachers = teachers;
    }
}

 

Student.java

package com.wedul.jpa.school;

import lombok.Builder;
import lombok.Getter;
import lombok.NoArgsConstructor;

import javax.persistence.*;

@Getter
@NoArgsConstructor
@Entity
@Table
public class Student {

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

    private String name;

    private Integer age;

    @ManyToOne
    @JoinColumn(name = "classes_id")
    private Classes classes;

    @Builder
    public Student(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public void updateClasses(Classes classes) {
        this.classes = classes;
    }
}

 

Teacher.java

package com.wedul.jpa.school;

import lombok.Builder;
import lombok.Getter;
import lombok.NoArgsConstructor;

import javax.persistence.*;

@Getter
@NoArgsConstructor
@Entity
@Table
public class Teacher {

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

    private String name;

    private Integer age;

    @ManyToOne
    @JoinColumn(name = "classes_id")
    private Classes classes;

    @Builder
    public Teacher(String name, Integer age, Classes classes) {
        this.name = name;
        this.age = age;
        this.classes = classes;
    }

    public void updateClasses(Classes classes) {
        this.classes = classes;
    }
}

 

fetch join

package com.wedul.jpa.school;

import org.springframework.data.jpa.repository.support.QuerydslRepositorySupport;

import static com.wedul.jpa.school.QClasses.classes;

public class ClassesCustomRepositoryImpl extends QuerydslRepositorySupport implements ClassesCustomRepository  {
    public ClassesCustomRepositoryImpl() {
        super(Classes.class);
    }

    @Override
    public Classes classes(long id) {
        return from(classes)
                .leftJoin(classes.students).fetchJoin()
                .leftJoin(classes.teachers).fetchJoin()
                .where(classes.id.eq(id))
                .fetchFirst();
    }
}

 

하지만 두개의 one to many관계를 fetch join으로 가져오려고 하니 MultipleBagFetchException이 발생했다.

에러 내용

Hibernate: 
    insert 
    into
        classes
        
    values
        ( )

org.springframework.dao.InvalidDataAccessApiUsageException: org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags: [com.wedul.jpa.school.Classes.students, com.wedul.jpa.school.Classes.teachers]; nested exception is java.lang.IllegalArgumentException: org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags: [com.wedul.jpa.school.Classes.students, com.wedul.jpa.school.Classes.teachers]

	at org.springframework.orm.jpa.EntityManagerFactoryUtils.convertJpaAccessExceptionIfPossible(EntityManagerFactoryUtils.java:374)
	at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:235)
	at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:551)
	at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:61)
	at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:242)
	at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:152)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:763)
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:708)
	at com.wedul.jpa.school.ClassesCustomRepositoryImpl$$EnhancerBySpringCGLIB$$aee1a338.classes(<generated>)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at org.springframework.data.repository.core.support.RepositoryMethodInvoker$RepositoryFragmentMethodInvoker.lambda$new$0(RepositoryMethodInvoker.java:289)
	at org.springframework.data.repository.core.support.RepositoryMethodInvoker.doInvoke(RepositoryMethodInvoker.java:137)
	at org.springframework.data.repository.core.support.RepositoryMethodInvoker.invoke(RepositoryMethodInvoker.java:121)
	at org.springframework.data.repository.core.support.RepositoryComposition$RepositoryFragments.invoke(RepositoryComposition.java:530)
	at org.springframework.data.repository.core.support.RepositoryComposition.invoke(RepositoryComposition.java:286)
	at org.springframework.data.repository.core.support.RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke(RepositoryFactorySupport.java:640)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.doInvoke(QueryExecutorMethodInterceptor.java:164)
	at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.invoke(QueryExecutorMethodInterceptor.java:139)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:81)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:123)
	at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:388)
	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:137)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:174)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:97)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:215)
	at com.sun.proxy.$Proxy110.classes(Unknown Source)
	at com.wedul.jpa.school.ClassesUseCaseServiceTest.test(ClassesUseCaseServiceTest.java:36)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:725)
	at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
	at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149)
	at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140)
	at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84)
	at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
	at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
	at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
	at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
	at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$7(TestMethodTestDescriptor.java:214)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:210)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:135)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:66)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:151)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
	at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
	at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:35)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:54)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:107)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:114)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:86)
	at org.junit.platform.launcher.core.DefaultLauncherSession$DelegatingLauncher.execute(DefaultLauncherSession.java:86)
	at org.junit.platform.launcher.core.SessionPerRequestLauncher.execute(SessionPerRequestLauncher.java:53)
	at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:57)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38)
	at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
Caused by: java.lang.IllegalArgumentException: org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags: [com.wedul.jpa.school.Classes.students, com.wedul.jpa.school.Classes.teachers]
	at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:141)
	at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:181)
	at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:188)
	at org.hibernate.internal.AbstractSharedSessionContract.createQuery(AbstractSharedSessionContract.java:757)
	at org.hibernate.internal.AbstractSharedSessionContract.createQuery(AbstractSharedSessionContract.java:114)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:362)
	at com.sun.proxy.$Proxy106.createQuery(Unknown Source)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:311)
	at com.sun.proxy.$Proxy106.createQuery(Unknown Source)
	at com.querydsl.jpa.impl.AbstractJPAQuery.createQuery(AbstractJPAQuery.java:132)
	at com.querydsl.jpa.impl.AbstractJPAQuery.fetchOne(AbstractJPAQuery.java:325)
	at com.querydsl.core.support.FetchableQueryBase.fetchFirst(FetchableQueryBase.java:51)
	at com.wedul.jpa.school.ClassesCustomRepositoryImpl.classes(ClassesCustomRepositoryImpl.java:18)
	at com.wedul.jpa.school.ClassesCustomRepositoryImpl$$FastClassBySpringCGLIB$$732f3ae8.invoke(<generated>)
	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218)
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:793)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:763)
	at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:137)
	... 102 more
Caused by: org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags: [com.wedul.jpa.school.Classes.students, com.wedul.jpa.school.Classes.teachers]
	at org.hibernate.loader.BasicLoader.postInstantiate(BasicLoader.java:76)
	at org.hibernate.loader.hql.QueryLoader.<init>(QueryLoader.java:110)
	at org.hibernate.hql.internal.ast.QueryTranslatorImpl.createQueryLoader(QueryTranslatorImpl.java:249)
	at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:213)
	at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:144)
	at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:113)
	at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:73)
	at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:162)
	at org.hibernate.internal.AbstractSharedSessionContract.getQueryPlan(AbstractSharedSessionContract.java:636)
	at org.hibernate.internal.AbstractSharedSessionContract.createQuery(AbstractSharedSessionContract.java:748)
	... 125 more

 

 

왜 에러가 발생했을까?

QueryLoader를 통해 Query 생성 시 작성한 querydsl을 토대로 SelectClause를 가지고 오게 된다. 이때 select 구문과 함께 조인으로 사용된 element들중 fetch join이 된 경우에는 collectionFromElement collection에 저장해서 반환해준다. 위에 예제에서는 select 본문과 student, teacher구문을 가지고 온다.

1. selectClause에서 조회 구문을 꺼내기
2. SelectCluse에서 fetch조인이 있을 경우 collectionFromElement에 추가하도록 추가

그 다음 SelectClause에 가지고 있는 collectionFromElement에 값이 있을 경우 그 collectionFromElement가 PersistentBag인 경우 개수가 2개 이상일경우 MultipleBagFetchException을 발생시킨다. 

왜 발생시킬까? PersistentBag은 하이버네이트가 컬렉션을 효율적으로 관리하기 위해 사용하는 컬렉션이다. 하지만 PersistentBag은 순서가 보장되지 않고 별도의 키로관리 되지 않기 때문에 알맞은 컬럼에 알맞은 엔티티에 매핑해서 사용하기 어렵기 때문에 두개 이상의 fetch join된 값을 사용할 수 없다.

 

해결법

Set을 사용

set의 경우 PersistentBag이 아닌 PersistentSet을 사용하기 때문에 Query 로드시 저 조건에 걸리지 않는다.  단, Set은 자료구조 특성상 중복허용과 순서 보장이 되지 않는 문제를 잘 생각하고 사용해야 한다.

bagRoles가 null이어서 Exception에 걸리지 않음

 

default batch fetch size 조정

fetch join을 하지말고 lazy loading으로 로드하여 사용하면 n+1 문제없이 로드해서 사용은 가능하다.

 

쿼리 나누기

두개이상의 조인 데이터를 한번에 호출하면 그만큼 쿼리 결과도 늦어지니 필요한 부분에서만 사용하도록 fetch join을 사용하기 보다 쿼리를 나눠서 진행해보자.

 

test github : https://github.com/weduls/multipleBagFetchException-test

 

GitHub - weduls/multipleBagFetchException-test: MultipleBagFetchException

MultipleBagFetchException. Contribute to weduls/multipleBagFetchException-test development by creating an account on GitHub.

github.com

https://thorben-janssen.com/hibernate-tips-how-to-avoid-hibernates-multiplebagfetchexception/

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