hibernate-orm/migration-guide.adoc

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

* link:https://github.com/hibernate/hibernate-orm/blob/6.1/migration-guide.adoc[6.1 Migration guide]
* link:https://github.com/hibernate/hibernate-orm/blob/6.0/migration-guide.adoc[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`.

=== Column type inference for `number(n,0)` in native SQL queries on Oracle

Previously, since Hibernate 6.0, columns of type `number` with scale 0 on Oracle were interpreted as `boolean`, `tinyint`, `smallint`, `int`, or `bigint`,
depending on the precision.

Now, columns of type `number` with scale 0 are interpreted as `int` or `bigint` depending on the precision.