If you are using GORM outside of Grails then you may need to manually flush the session at the end of your operation.
If you want to continue to use Hibernate 4 you must explicitly declare the Hibernate 4 dependences in compile("org.grails:gorm-hibernate5-spring-boot:6.1.8.
There are currently several implementations of GORM.
This documentation covers the original implementation of GORM which is based on the Hibernate ORM. Required by: project :example is the new default flush mode in GORM 6, which will flush the session on transaction commit.
For example consider the following code: In this example the association link is being created by the child (Book) and hence it is not necessary to manipulate the collection directly resulting in fewer queries and more efficient code.
Given an A key thing to remember about GORM is that under the surface GORM is using Hibernate for persistence.