The code in org.hibernate.search.query.engine.impl.LazyQueryState.validateQuery() has an impact on performance and we should be able to rethink it in some smart way.

For example, I suspect we're currently collecting all fieldnames for each cathegory to simplify the code and make it easy to throw a user-friendly exception, but I wonder if we could attempt an "optimistic validation" which doesn't collect anything unless something is actually wrong, in that case we can fall back to the slower strategy to still show a user friendly error.