Hibernate hi/lo Algorithm And External Systems Issue

Description: This is a Spring Boot sample that exemplifies how the hi/lo algorithm may cause issues when the database is used by external systems as well. Such systems can safely generate non-duplicated identifiers (e.g., for inserting new records) only if they know about the hi/lo presence and its internal work. So, better rely on pooled or pooled-lo algorithm which doesn't cause such issues.

Key points:

• use the SEQUENCE generator type (e.g., in PostgreSQL)
• configure the hi/lo algorithm as in Author.java entity
• insert a few records via hi/lo
• insert a few records natively (this acts as an external system that relies on NEXTVAL('hilo_sequence') and is not aware of hi/lo presence and/or behavior)

Output sample: Running this application should result in the following error:
ERROR: duplicate key value violates unique constraint "author_pkey"
Detail: Key (id)=(2) already exists.

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