我想以一种可以对我的系统恢复的方式重命名PostgreSQL（9.6）表（使用JPA / Hibernate的Java应用程序）
在我的Java代码中，JPA实体将具有以下注释@Entity @Table(name="old_name")，而数据库将具有一个等效表old_name。
我想将表重命名为new_name，以便可以逐步更新数据库和Java应用程序，从而允许失败和回滚。
典型步骤是
old_name中创建new_name的副本new_name old_name 有效地，我希望在具有相同数据的相同模式下的重复表能够接收来自JPA实体的读取和写入。
我知道触发器的使用，并希望避免这种情况。我希望有一种我不知道也没有发现的技术，比使用触发器可以减轻痛苦。
我试图重命名该表并在其上创建一个“简单视图”，但是JPA实体抱怨，因为它找不到带有视图名称的表。 （因为它是一个视图，而不是一个表:)，而且似乎没有@ View / @ Table JPA批注可以处理此问题）
我还没有尝试过这里列出的功能：http://wiki.postgresql.org/wiki/Replication,_Clustering,_and_Connection_Pooling，因为大多数功能似乎是关于池化，分片的，并且我需要一个简单的短期表副本，但是我还将对此进行调查。
谢谢-我当然想要最简单的选择，宁愿使用postgres / JPA中内置的东西，但也会认真考虑第三者的选择。
答案 0 :(得分：6)
假设您有以下两个表：
1 CREATE TABLE old_post (
id int8 NOT NULL,
title varchar(255),
version int4 NOT NULL,
PRIMARY KEY (id)
)
CREATE TABLE post (
id int8 NOT NULL,
created_on date,
title varchar(255),
version int4 NOT NULL,
PRIMARY KEY (id)
)
表必须与较新的old_post复制。请注意，post表现在具有比旧表更多的列。
我们只需要映射post实体：
Post现在，我们必须注册3个事件侦听器，以拦截@Entity(name = "Post")
@Table(name = "post")
public static class Post {
@Id
private Long id;
private String title;
@Column(name = "created_on")
private LocalDate createdOn = LocalDate.now();
@Version
private int version;
//Getters and setters omitted for brevity
}
实体的INSERT，UPDATE和DELETE操作。
我们可以通过以下事件侦听器执行此操作：
Post可以使用休眠public class ReplicationInsertEventListener
implements PostInsertEventListener {
public static final ReplicationInsertEventListener INSTANCE =
new ReplicationInsertEventListener();
@Override
public void onPostInsert(
PostInsertEvent event)
throws HibernateException {
final Object entity = event.getEntity();
if(entity instanceof Post) {
Post post = (Post) entity;
event.getSession().createNativeQuery(
"INSERT INTO old_post (id, title, version) " +
"VALUES (:id, :title, :version)")
.setParameter("id", post.getId())
.setParameter("title", post.getTitle())
.setParameter("version", post.getVersion())
.setFlushMode(FlushMode.MANUAL)
.executeUpdate();
}
}
@Override
public boolean requiresPostCommitHanding(
EntityPersister persister) {
return false;
}
}
public class ReplicationUpdateEventListener
implements PostUpdateEventListener {
public static final ReplicationUpdateEventListener INSTANCE =
new ReplicationUpdateEventListener();
@Override
public void onPostUpdate(
PostUpdateEvent event) {
final Object entity = event.getEntity();
if(entity instanceof Post) {
Post post = (Post) entity;
event.getSession().createNativeQuery(
"UPDATE old_post " +
"SET title = :title, version = :version " +
"WHERE id = :id")
.setParameter("id", post.getId())
.setParameter("title", post.getTitle())
.setParameter("version", post.getVersion())
.setFlushMode(FlushMode.MANUAL)
.executeUpdate();
}
}
@Override
public boolean requiresPostCommitHanding(
EntityPersister persister) {
return false;
}
}
public class ReplicationDeleteEventListener
implements PreDeleteEventListener {
public static final ReplicationDeleteEventListener INSTANCE =
new ReplicationDeleteEventListener();
@Override
public boolean onPreDelete(
PreDeleteEvent event) {
final Object entity = event.getEntity();
if(entity instanceof Post) {
Post post = (Post) entity;
event.getSession().createNativeQuery(
"DELETE FROM old_post " +
"WHERE id = :id")
.setParameter("id", post.getId())
.setFlushMode(FlushMode.MANUAL)
.executeUpdate();
}
return false;
}
}
注册3个事件侦听器：
Integrator并且，要指示Hibernate使用此自定义public class ReplicationEventListenerIntegrator
implements Integrator {
public static final ReplicationEventListenerIntegrator INSTANCE =
new ReplicationEventListenerIntegrator();
@Override
public void integrate(
Metadata metadata,
SessionFactoryImplementor sessionFactory,
SessionFactoryServiceRegistry serviceRegistry) {
final EventListenerRegistry eventListenerRegistry =
serviceRegistry.getService(EventListenerRegistry.class);
eventListenerRegistry.appendListeners(
EventType.POST_INSERT,
ReplicationInsertEventListener.INSTANCE
);
eventListenerRegistry.appendListeners(
EventType.POST_UPDATE,
ReplicationUpdateEventListener.INSTANCE
);
eventListenerRegistry.appendListeners(
EventType.PRE_DELETE,
ReplicationDeleteEventListener.INSTANCE
);
}
@Override
public void disintegrate(
SessionFactoryImplementor sessionFactory,
SessionFactoryServiceRegistry serviceRegistry) {
}
}
，您需要设置Integrator配置属性：
hibernate.integrator_provider现在，在保留<property name="hibernate.integrator_provider"
value="com.vladmihalcea.book.hpjp.hibernate.listener.ReplicationEventListenerIntegrator "/>
实体时：
PostHibernate将执行以下SQL INSERT语句：
Post post1 = new Post();
post1.setId(1L);
post1.setTitle(
"The High-Performance Java Persistence book is to be released!"
);
entityManager.persist(post1);
在进行另一项更新现有Query:["INSERT INTO old_post (id, title, version) VALUES (?, ?, ?)"], Params:[(1, The High-Performance Java Persistence book is to be released!, 0)]
Query:["insert into post (created_on, title, version, id) values (?, ?, ?, ?)"], Params:[(2018-12-12, The High-Performance Java Persistence book is to be released!, 0, 1)]
实体并创建新的Post实体的交易时：
Post Hibernate还将所有操作复制到Post post1 = entityManager.find(Post.class, 1L);
post1.setTitle(post1.getTitle().replace("to be ", ""));
Post post2 = new Post();
post2.setId(2L);
post2.setTitle(
"The High-Performance Java Persistence book is awesome!"
);
entityManager.persist(post2);
表中：
old_post删除 Query:["select tablerepli0_.id as id1_1_0_, tablerepli0_.created_on as created_2_1_0_, tablerepli0_.title as title3_1_0_, tablerepli0_.version as version4_1_0_ from post tablerepli0_ where tablerepli0_.id=?"], Params:[(1)]
Query:["INSERT INTO old_post (id, title, version) VALUES (?, ?, ?)"], Params:[(2, The High-Performance Java Persistence book is awesome!, 0)]
Query:["insert into post (created_on, title, version, id) values (?, ?, ?, ?)"], Params:[(2018-12-12, The High-Performance Java Persistence book is awesome!, 0, 2)]
Query:["update post set created_on=?, title=?, version=? where id=? and version=?"], Params:[(2018-12-12, The High-Performance Java Persistence book is released!, 1, 1, 0)]
Query:["UPDATE old_post SET title = ?, version = ? WHERE id = ?"], Params:[(The High-Performance Java Persistence book is released!, 1, 1)]
实体时：
Post Post post1 = entityManager.getReference(Post.class, 1L);
entityManager.remove(post1);
记录也被删除：
old_post有关更多详细信息，请查看this article。
在GitHub上可用的代码。