Is it possible to create hierarchical facets like states - cities?
So the first level shows entries grouped by states and below the second level grouped by cities, like a tree structure.

Thanks

of course

Well, does the api support this? I don't see it.
Of course I can create two facets and combine them after execution "by hand".
My idea was that a Facet object has a set of sub Facets, already filled when returning from getFacets().

Well I'm not very practical with that API myself, but these two functional tests aim to mimick the "drill down" menus as found on many web shops:

https://github.com/hibernate/hibernate- ... pTest.java
https://github.com/hibernate/hibernate- ... gTest.java

org.hibernate.search.test.query.facet.FacetFilteringTest
org.hibernate.search.test.query.facet.WebShopTest

hope it helps; If I didn't understand your question could you post an example of what you're needing to do?

Thanks for the examples.
However, these have independent, one-level facets (color, size).
In my case I am looking for a hierarchy of facets like cities within a state. The city facet elements depend on the superior state facet element.
Ideally, one would define this structure for the facets and the execution of the query returns the state facets, each with a set of city facets.
But I think hibernate search does not support this currently. So I will implement two independent facets and combine them in my code.

Another way to explain what I am looking for is the SQL equivalent: a 'group by' of various columns:
group by state_id, city_id order by state_name, city_name

This seems not to be possible with HS facets. The workaround equivalent in SQL is to execute two selects
group by state_id
group by city_id
and to combine the result in my code, looping over both result sets.

Hi,



That the facets are related is really a semantic problem. The question is whether the API allows for calculations for sub facets. It does not matter whether these facets are related or not semantically. The size facet of the example can be treated as a sub-facet of the color facet as well.
That said, there is indeed no API to select a facet and automatically calculate all selected sub facets. You would have to loop through your first facet, call facetManager.getFacetGroup( "myFacetName" ).selectFacets( selectedFacet ) and then inspect the result for the second facet. Very similar to what happens in the test mentioned above, but just in a loop.



Do you have any concrete ideas on how the API should look like. We are in the process on extending faceting (see HSEARCH-809 and in the process of collecting requirements. The new approach uses Lucene's native faceting which knows the concept of category path. I think that goes into the direction your want to go. There are several questions around this topic. First of all the new approach requires that you make faceting decisions (configuration) at index time. ATM, faceting uses the standard index information and you can facet on any discrete field without configuring this field for faceting. This need to to change and we probably end up adding a new annotation, for example @FacetPath. But how to do connect two entity properties and create a nested category path via annotations.
The other question is how to extend the FacetManager API to enable sub-faceting.
I am aware that this goes now far beyond your initial question, but I am looking for feedback on improving the current API and all help is welcome :-)

--Hardy

Thanks for the detailed reply.
Currently I am drowned in work, we are just a few days before a production release.
I hope to give it a thought as soon as I can.

Cheers,
Ulrich