= 6.2 Migration Guide
:toc:
:toclevels: 4
:docsBase: https://docs.jboss.org/hibernate/orm/6.2
:userGuideBase: {docsBase}/userguide/html_single/Hibernate_User_Guide.html
:javadocsBase: {docsBase}/javadocs


This guide discusses migration from Hibernate ORM version 6.2. For migration from
earlier versions, see any other pertinent migration guides as well.

* link:../../../6.1/migration-guide/migration-guide.html[6.1 Migration guide]
* link:../../../6.0/migration-guide/migration-guide.html[6.0 Migration guide]

== Default DDL type changes

=== UUID mapping changes on MariaDB

On MariaDB, the type code `SqlType.UUID` now by default refers to the DDL type `uuid`, whereas before it was using `binary(16)`.
Due to this change, schema validation errors could occur on existing databases.

The migration to `uuid` requires a migration expression like `cast(old as uuid)`.

To retain backwards compatibility, configure the setting `hibernate.type.preferred_uuid_jdbc_type` to `BINARY`.

=== UUID mapping changes on SQL Server

On SQL Server, the type code `SqlType.UUID` now by default refers to the DDL type `uniqueidentifier`, whereas before it was using `binary(16)`.
Due to this change, schema validation errors could occur on existing databases.

The migration to `uuid` requires a migration expression like `cast(old as uuid)`.

To retain backwards compatibility, configure the setting `hibernate.type.preferred_uuid_jdbc_type` to `BINARY`.
