Looking at the failing tests, they all seem to only work for Mongo really, right?

	@SkipByGridDialect(
			value = { GridDialectType.CASSANDRA, GridDialectType.COUCHDB, GridDialectType.EHCACHE, GridDialectType.HASHMAP, GridDialectType.INFINISPAN },
			comment = "Hibernate Search cannot project multiple values from the same field at the moment" )

I take it that for MongoDB we are not using Hibernate Search under the hood for executing JP-QL queries, but some sort of native Mongo queries. I am wondering where this is handled in the code?

Also the documentation says:

Inner JOIN on an embedded association is partially supported. In particular, filtering the elements of the association works for all the datastores but projecting properties won’t work if you are using Hibernate Search queries.

First off, should this not really be:

Inner JOIN on an embedded association is partially supported. In particular, filtering the elements of the association works for all the datastores but projecting properties won’t work if your datastore provider implements JP-QL queries using Hibernate Search.

The current wording suggest that you are literally using Hibernate Search queries which is imo confusing.

The other thing I am wondering is, how a user knows how for example JP-QL queries are implemented. I can see that some datastore providers have a dedicated section for this. For example, MongoDB (Section 11.5) and Neo4J (Section 12.5). Others don't necessarily have this information. I think it would be important to have some symmetry here between the datastore specific documentation. Or have even somewhere some matrix which list several important details/criteria and if/how they are implemented/available for each data store.