Postgres + EJB3 预分配大小错误答案

【问题标题】：Postgres + EJB3 pre-allocation size errorPostgres + EJB3 预分配大小错误
【发布时间】：2012-03-17 16:36:43
【问题描述】：

我在 postgres 和 jpa 中遇到了序列问题

Caused by: javax.persistence.EntityExistsException:
Exception Description: The sequence named [shp_users_seq] is setup incorrectly.  Its increment does not match its pre-allocation size.
        at org.eclipse.persistence.internal.jpa.EntityManagerImpl.persist(EntityManagerImpl.java:443)
        at com.sun.enterprise.container.common.impl.EntityManagerWrapper.persist(EntityManagerWrapper.java:269)
        at base.data.provider.beans.session.DAOImpl.createUser(DAOImpl.java:18)

【问题讨论】：

标签： ejb-3.0 jpa-2.0 glassfish-3 postgresql-9.1

【解决方案1】：

尝试将序列的起始值设置为至少与您用于 @SequenceGenerator 注释的属性 allocationSize 的大小相同。

 CREATE SEQUENCE seq_name
 ...
 START WITH 100;

详情请参阅http://dev.eclipse.org/mhonarc/lists/eclipselink-users/msg03461.html。

【讨论】：

【解决方案2】：

规则是：序列的增量大小是jpa中allocationSize的值：我有这个设置：这是错误的：

@SequenceGenerator(name = "User_Seq_Gen", 
                   sequenceName = "shp_users_seq", allocationSize=999)

据此更正：

@SequenceGenerator(name = "User_Seq_Gen", 
                   sequenceName = "shp_users_seq" ,allocationSize=1)

因为序列的增量大小是1：

 shopper=> \d shp_users_seq;
        Sequence "public.shp_users_seq"
    Column     |  Type   |        Value
---------------+---------+---------------------
 sequence_name | name    | shp_users_seq
 last_value    | bigint  | 1
 start_value   | bigint  | 1
 increment_by  | bigint  | 1
 max_value     | bigint  | 9223372036854775807
 min_value     | bigint  | 1
 cache_value   | bigint  | 1
 log_cnt       | bigint  | 0
 is_cycled     | boolean | f
 is_called     | boolean | t

【讨论】：