当为 Postgres DB 的属性 spring.jpa.hibernate.ddl-auto 提供更新值时，Hibernate 不会生成序列

Question

When I use spring.jpa.hibernate.ddl-auto=create, sequences and tables are both created but when this property is set to update, only the tables are getting created. I have created a spring boot application and for DB, I am using Postgres. But when I check the same for h2 database (which is embedded), the sequences and the tables get created for the update value as well. I can not set the property to create as it will drop the tables when the application restarts. Can somebody please enlighten me? Thanks in advance.

Answer 1

you can read about ddl-auto-generation in spring doc

link: https://docs.spring.io/spring-boot/docs/1.0.x-SNAPSHOT/reference/html/howto-database-initialization.html

Or

https://www.baeldung.com/spring-boot-data-sql-and-schema-sql

Answer 2

There was a bug in hibernate related to Postgres dialect. Below is the method in PostgresSQLDialect to check if sequence is present in schema (which is wrong by the way):

@Override
    public String getQuerySequencesString() {
        return "select relname from pg_class where relkind='S'";
    }

The above query returns sequences if there is any sequence present in any schema in the database. And if there is any schema containing any sequence, it won't create sequences in the specified schema of that Database. To resolve this, I wrote a custom Postgres dialect and changed the query to following:

@Override
public String getQuerySequencesString() {
    return "select sequencename from pg_catalog.pg_sequences where schemaname='"+schemaName+"'";
}

It resolves the issue when ddl-auto is set to update. The sequences are getting created now.