问题描述

我使用的是 hibernate 3，oracle 10g.我有一张桌子:主题.定义在这里

I am using hibernate 3 , oracle 10g. I have a table: subject. The definition is here

CREATE TABLE SUBJECT
    ( 
     SUBJECT_ID NUMBER (10), 
     FNAME VARCHAR2(30)  not null, 
     LNAME VARCHAR2(30)  not null, 
     EMAILADR VARCHAR2 (40),
     BIRTHDT  DATE       not null,
     constraint pk_sub primary key(subject_id) USING INDEX TABLESPACE data_index
    ) 
;

插入新主题时，sub_seq用于创建主题id，定义在这里

when insert a new subject, sub_seq is used to create an subject id, the definition is here

create sequence sub_seq
       MINVALUE 1 
       MAXVALUE 999999999999999999999999999 
       START WITH 1
       INCREMENT BY 1 
       CACHE 100 
       NOCYCLE ;

Subject 类是这样的:

the Subject class is like this:

@Entity
@Table(name="ktbs.syn_subject")
public class Subject {

    @Id 
    @Column(name="subject_id")
    @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="SUB_SEQ")
    @SequenceGenerator(name="SUB_SEQ", sequenceName = "SUB_SEQ")
    private long subjectId;
    private String fname;
    private String lname;
    private String emailadr;
    private Date birthdt;
}

在主题表中，数据库中有 4555 个主题由来自 excel 的 plsql 脚本加载，并且 sub_sequence 工作正常.主题 ID 范围为 1--4555.

in the subject table , there have been 4555 subjects in the database loaded by plsql scripts from excel and the sub_sequence worked fine. subject ids range from 1--4555.

但是，当我使用 hibernate 从我的应用程序中添加一个主题时，序号跳到了255050，运行几天后hibernate生成的subject id是这样的

however, when i added a subject from my application using hibernate, the sequence number jumped to 255050. After several days running, the subject ids generated by hibernate look like this

270079
270078
270077
270076
270075
270074
270073
270072
270071
270070
270069
270068
270067
270066
270065
270064
270063
270062
270061
270060
270059
270058
270057
270056
270055
270054
270053
270052
270051
270050
265057
265056
265055
265054
265053
265052
265051
265050
260059
260058
260057
260056
260055
260054
260053
260052
260051
260050
255067
255066
255065
255064
255063
255062
255061
255060
255059
255058
255057
255056
255055
255054
255053
255052
255051
255050
4555
4554
4553
.
.
.
.
1

有几个大的差距:4555到255051、255067到260051、265057到270051

There are several large gaps: 4555 to 255051, 255067 to 260051, 265057 to 270051

这是一种浪费，而不是一种理想的行为.

this is a waste and not a desired behavior.

有谁知道为什么会发生这种情况并且很容易修复它

does anyone know why this happens and hot to fix it

谢谢

推荐答案

我认为问题出在序列生成器并不是真正的序列生成器，而是序列hilo生成器，默认分配大小为50. 如文档所示:http:///docs.jboss.org/hibernate/stable/annotations/reference/en/html_single/#entity-mapping-identifier

I think that the problem comes from the fact that the sequence generator is not really a sequence generator, but a sequence hilo generator, with a default allocation size of 50. as indicated by the documentation : http://docs.jboss.org/hibernate/stable/annotations/reference/en/html_single/#entity-mapping-identifier

这意味着如果序列值为 5000，则下一个生成的值将是 5000 * 50 = 250000.将序列的缓存值添加到等式中，它可能解释了您巨大的初始差距.

This means that if the sequence value is 5000, the next generated value will be 5000 * 50 = 250000. Add the cache value of the sequence to the equation, and it might explain your huge initial gap.

检查序列的值.它应该小于最后生成的标识符.注意不要将序列重新初始化为最后生成的值 + 1，因为生成的值会呈指数增长(我们遇到过这个问题，并且由于溢出而导致负整数 id)

Check the value of the sequence. It should be less than the last generated identifier. Be careful not to reinitialize the sequence to this last generated value + 1, because the generated valus would grow exponentially (we've had this problem, and had negative integer ids due to overflow)

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