将 oracle 序列与 jpa 一起使用（toplink）
我的 oracle 数据库中有一个序列对象：
create sequence BASE_SEQ
minvalue 1
maxvalue 9999999999999999999999999999
start with 100
increment by 1
nocache;
我将 jpa(toplink) 用于我的 Web 应用程序。我的所有数据库对象都有基类：
@MappedSuperclass
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class AbstractEntity implements Serializable {
protected BigDecimal id;
@javax.persistence.Column(name = "ID")
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "BASE_SEQ")
@SequenceGenerator(name="BASE_SEQ",sequenceName="BASE_SEQ", catalog = "DOF")
public BigDecimal getId() {
return id;
}
此类由某些实体继承。在我启动我的应用程序并将多个实体持久/合并到数据库后，我可以发现它们的 PK 以 51 开头（而不是预期的 100）。
之后，我转到数据库，查看序列对象的 DDL，发现它已更改为：
create sequence BASE_SEQ
minvalue 1
maxvalue 9999999999999999999999999999
start with 101
increment by 1
nocache;
为什么会发生这种情况？我有一些 PK 51、52 ... 等的实体，序列以 101 开头。AS
- GlassFish 3.1.1
I have a sequence object in my oracle db:
create sequence BASE_SEQ
minvalue 1
maxvalue 9999999999999999999999999999
start with 100
increment by 1
nocache;
I use jpa(toplink) for my web application. I have base class for all my db objects:
@MappedSuperclass
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class AbstractEntity implements Serializable {
protected BigDecimal id;
@javax.persistence.Column(name = "ID")
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "BASE_SEQ")
@SequenceGenerator(name="BASE_SEQ",sequenceName="BASE_SEQ", catalog = "DOF")
public BigDecimal getId() {
return id;
}
This class is inherited by some entities. After I start my application, and persist/merge several entities to db, i can find, that theirs' PK starts with 51 (instead of expected 100).
After that, I go to my db, view DDL of my sequence object and see, that it has been changed to:
create sequence BASE_SEQ
minvalue 1
maxvalue 9999999999999999999999999999
start with 101
increment by 1
nocache;
Why so happens? I have some entities with PK 51, 52 ... etc, and sequence starting with 101.
AS - GlassFish 3.1.1
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SequenceGenerator 上的默认 preallocationSize 为 50，它必须与您设置为 1 的序列增量相匹配
。将增量更改为 50（推荐），或将 preallocationSize 更改为 1（这将导致插入性能不佳）。
The default preallocationSize on SequenceGenerator is 50, it must match your sequence increment, which you have set to 1.
Either change your increment to 50 (recommended), or change your preallocationSize to 1 (this will result in poor insert performance).