PostgreSQL: java.util.Instant - Hibernate creates column with typecode 93 and then expects typecode 3003

What was observed?

Windows + PostgreSQL 10 or 14 Database / Linux + PostgreSQL 10 Database

Hibernate throws the following schema validation exception:

org.hibernate.tool.schema.spi.SchemaManagementException: Schema-validation: wrong column type encountered in column [mycolumn] in table [mytable]; found [timestamptz (Types#TIMESTAMP)], but expecting [timestamp(6) with time zone (Types#TIMESTAMP_UTC)]

The underlying Java datatype is java.util.Instant.

Additional Information

In both databases the information_schema describes the column as

The column in the windows database was created with an DDL statement containing timestamp(6) with time zone as datatype which was extracted from the linux database which had been created by hibernate with hibernate.hbm2ddl.auto=create-drop.

Recent tests showed that the bug also occurs in the linux installation when the application is redeployed. That means, hibernate is rejecting the datatype it created before.

What is the Bug?

After some analysis I could pin down the bug.

Hibernate creates the column as timestamp(6) with timezone which is later interpreted as a TIMESTAMP column (typeCode 93).
But since the Java type is a java.util.Instant typeCode 3003 is expected.

What is the impact?

PostgreSQL Schemas created by Hibernate that contain java.util.Instant can not be successfully validated by Hibernate under default settings. Therefore, in my opinion, the priority of this is Critical.

Workaround

Set hibernate.type.preferred_instant_jdbc_type=93