休眠oracle序列产生大间隙

2021-12-05 00:00:00 sequence oracle Hibernate gaps-in-data

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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