When migrating from Hibernate Search 5.2.1.Final to 5.5.4.Final, we detected an undocumented behavior change in the faceting API (probably introduced with 5.3.0.Final).

The Javadoc of method maxFacetCount in interface org.hibernate.search.query.dsl.FacetParameterContext states:

maxFacetCount - the maximum number of facets to include in the response. A negative value means that all facets will be included

In fact a negative value means that the number of facets is limited to 100. This is also the default when not using maxFacetCount at all.

This behavior has changed in comparison to 5.2.1.Final, where the number of facets was unlimited by default.

The migration guide (Hibernate Search 5.2.x to 5.3.x) only refers to the changed behavior related to includeZeroCounts, but not regarding maxFacetCount:

• http://hibernate.org/search/documentation/migrate/5.3/
• http://in.relation.to/2015/05/11/hibernate-search-530-beta-1-with-native-lucene-faceting/

I would suggest to adjust the Javadoc and the migration guide. It would also be interesting if there was a specific reason for this behavior change.