How does spring.jpa.hibernate.ddl-auto property exactly work in Spring?
ddl, hibernate, java, jpa, spring
Solution
For the record, the `spring.jpa.hibernate.ddl-auto` property is Spring Data JPA specific and is their way to specify a value that will eventually be passed to Hibernate under the property it knows, `hibernate.hbm2ddl.auto`.
The values `create`, `create-drop`, `validate`, and `update` basically influence how the schema tool management will manipulate the database schema at startup.
For example, the `update` operation will query the JDBC driver's API to get the database metadata and then Hibernate compares the object model it creates based on reading your annotated classes or HBM XML mappings and will attempt to adjust the schema on-the-fly.
The `update` operation for example will attempt to add new columns, constraints, etc but will never remove a column or constraint that may have existed previously but no longer does as part of the object model from a prior run.
Typically in test case scenarios, you'll likely use `create-drop` so that you create your schema, your test case adds some mock data, you run your tests, and then during the test case cleanup, the schema objects are dropped, leaving an empty database.
In development, it's often common to see developers use `update` to automatically modify the schema to add new additions upon restart. But again understand, this does not remove a column or constraint that may exist from previous executions that is no longer necessary.
In production, it's often highly recommended you use `none` or simply don't specify this property. That is because it's common practice for DBAs to review migration scripts for database changes, particularly if your database is shared across multiple services and applications.
Problem
I was working on my Spring boot app project and noticed that, sometimes there is a connection time out error to my Database on another server(SQL Server). This happens specially when I try to do some script migration with `FlyWay` but it works after several tries. Then I noticed that I didn't specify `spring.jpa.hibernate.ddl-auto` in my properties file. I did some research and found that it is recommended to add `spring.jpa.hibernate.ddl-auto= create-drop` in development. And change it to: `spring.jpa.hibernate.ddl-auto= none` in production. But I didn't actually understand how does it really work and how does hibernate generate database schema using `create-drop` or `none` value. Can you please explain technically how does it really work, and what are recommendations for using this property in development and on a production server. Thank you