Column ordering leads to wrong column order in unique constraints

Given

Note that we define an explicit unique constraint on the columns (b, a) (in that very order). The column order could be important since the underlying unique index should be used to speed-up queries that select all entities for a given value of “b”.

Actual vs. Expected

When the schema gets created in the context of a JPA EntityManagerFactory, the columns are (re-)ordered during construction of the SessionFactoryImpl, Line 252: bootMetamodel.orderColumns( false )

This leads to the following DDL:

Note that “uk_b_a” is created with columns (a, b) instead of the expected column order (b, a).

Workaround

One can restore the behavior of Hibernate 6.1 by switching to the legacy column ordering strategy via hibernate.column_ordering_strategy=legacy.

Test Case