The main advantage compared to client-side event sourcing would be the ability to detect "batch" changes caused by update/delete queries, which currently are not detected.
For example if the user updates the property name in a thousand Person entities using UPDATE Person p SET p.name = CONCAT(p.name, 'foo'), this change currently is never detected by Hibernate Search. The user has to take care to reindex affected entities manually.
Once HSEARCH-3281 is addressed, we will have most of the infrastructure ready to support Debezium in Hibernate Search. The main problem will be to create a Debezium plugin that allows to:
Define the events we're interested in at the Hibernate ORM entity level, instead of the table level (i.e. translate"I'm interested in property myEmbeddable.property1 of entity MyEntity" into "I'm interested in column myEmbeddable_property1 of table myentity".
Ideally, send entity-scoped events instead of table-scoped event, with the same format as what we envision for entity change events in HSEARCH-3281
Optimistically planning this for 6.1, but we will need to work very hard with the Debezium team to address the two points above.