Java Hibernate_sequence表生成
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Hibernate_sequence table is generated
提问by Vitalii Kravchenko
I have id column with generated strategy AUTO, I'm wondering, why MySql generate hibernate_sequence table? I supposed that hibernate will pick IDENTITY id generating strategy
我有带有生成策略 AUTO 的 id 列，我想知道，为什么 MySql 生成 hibernate_sequence 表？我认为 hibernate 会选择 IDENTITY id 生成策略
<mapped-superclass class="com.cl.xlp.model.data.Identity">
<attributes>
<id name="id">
<column name="id" />
<generated-value strategy="AUTO" />
</id>
</attributes>
</mapped-superclass>
Hibernate properties
休眠属性
hibernate.dialect=org.hibernate.dialect.MySQL5Dialect
hibernate.hbm2ddl.auto=update
Mysql connector version
Mysql 连接器版本
version.mysql.connector>5.1.39</version.mysql.connector>
Mysql server version is 5.6.12
Mysql服务器版本是5.6.12
回答by Poly
If you use strategy="AUTO", Hibernate will generate a table called hibernate_sequenceto provide the next number for the IDsequence. You may have forgotten to add the AutoIncrementfeature to your table's PK.
如果您使用strategy="AUTO"，Hibernate 将生成一个表，称为hibernate_sequence提供ID序列的下一个编号。您可能忘记将该AutoIncrement功能添加到您的表的 PK 中。
You may use generation strategy strategy="IDENTITY"to enforce using the AutoIncrementfeature available in MySql and avoid creating a table.
您可以使用生成策略strategy="IDENTITY"来强制使用AutoIncrementMySql 中可用的功能并避免创建表。
回答by Kamalesh Patil
The way Hibernate interprets AUTO generation type has changed starting with Hibernate version 5.0.
从 Hibernate 5.0 版开始，Hibernate 解释 AUTO 生成类型的方式发生了变化。
When using Hibernate v 4.0 and Generation Type as AUTO, specifically for MySql, Hibernate would choose the IDENTITYstrategy (and thus use the AUTO_INCREMENTfeature) for generating IDs for the table in question.
当使用 Hibernate v 4.0 和 Generation Type as 时AUTO，特别是对于 MySql，Hibernate 会选择IDENTITY策略（并因此使用该AUTO_INCREMENT功能）来为相关表生成 ID。
Starting with version 5.0 when Generation Type is selected as AUTO, Hibernate uses SequenceStyleGeneratorregardless of the database. In case of MySql Hibernate emulates a sequence using a table and is why you are seeing the hibernate_sequence table. MySql doesn't support the standard sequence type natively.
从 5.0 版本开始，当 Generation Type 选择为 AUTO 时，Hibernate 使用SequenceStyleGenerator而不考虑数据库。在 MySql Hibernate 使用表模拟序列的情况下，这就是您看到 hibernate_sequence 表的原因。MySql 本身不支持标准序列类型。
References
参考
