Hey Michael-
You've gotten a lot of great information here already. I'll point you to
one more implementation as well: StringValueFacetCounts. This
implementation lets you do faceting over arbitrary "string-like" doc value
fields (SORTED and SORTED_SET). So if you already have a field of this type
you're using for other purposes, and you want to do faceting over it, you
can do it with this implementation.
The faceting-specific fields (there's a taxonomy-based approach and a
non-taxonomy-based approach, both with pros/cons) are also available, which
is what you've referenced here so far (and what others have pointed you
to). These are more "managed" fields with faceting in mind.
A high-level difference here is that faceting-specific fields tend to index
all the facet fields into a single doc values field in the index, which can
make faceting more efficient. StringValueFacetCounts can be less efficient
for faceting (if you have many different fields you want to individually
facet) but could be more flexible for you if you already have these fields
in your index for other purposes and don't want to duplicate the data into
these facet-specific fields.
Not sure if these details are helpful for you or not. If any of this is a
bit unclear, let me know and I'll try to describe things better or answer
specific questions. Honestly, we probably have too many ways to do the same
thing in the faceting module, and maybe our documentation could be a bit
more helpful.
Cheers,
-Greg
On Fri, Oct 20, 2023 at 2:54?PM Michael Wechner <michael.wechner@wyona.com>
wrote:
> thanks very much for this additional information, Marc!
>
> Am 20.10.23 um 20:30 schrieb Marc D'Mello:
> > Just following up on Mike's comment:
> >
> >
> >> It used to be that the "doc values" based faceting did not support
> >>
> > arbitrary hierarchy, but I think that was fixed at some point.
> >
> >
> > Yeah it was fixed a year or two ago, SortedSetDocValuesFacetField
> supports
> > hierarchical faceting, I think you just need to enable it in the
> > FacetsConfig. One thing to keep in mind is even though SSDV faceting
> > doesn't require a taxonomy index, it still requires a
> > SortedSetDocValuesReaderState to be maintained, which can be a little bit
> > expensive to create, but only needs to be done once. This benchmark code
> > <
> https://github.com/mikemccand/luceneutil/blob/master/src/main/perf/facets/BenchmarkFacets.java
> >
> > serves as a pretty basic example of SSDV/hierarchical SSDV faceting.
> >
> > On Fri, Oct 20, 2023 at 7:09?AM Michael Wechner <
> michael.wechner@wyona.com>
> > wrote:
> >
> >> cool, thank you very much!
> >>
> >> Michael
> >>
> >>
> >>
> >> Am 20.10.23 um 15:44 schrieb Michael McCandless:
> >>> You can use either the "doc values" implementation for facets
> >>> (SortedSetDocValuesFacetField), or the "taxonomy" implementation
> >>> (FacetField, in which case, yes, you need to create a TaxonomyWriter).
> >>>
> >>> It used to be that the "doc values" based faceting did not support
> >>> arbitrary hierarchy, but I think that was fixed at some point.
> >>>
> >>> Mike McCandless
> >>>
> >>> http://blog.mikemccandless.com
> >>>
> >>>
> >>> On Fri, Oct 20, 2023 at 9:03?AM Michael Wechner <
> >> michael.wechner@wyona.com>
> >>> wrote:
> >>>
> >>>> Hi Mike
> >>>>
> >>>> Thanks for your feedback!
> >>>>
> >>>> IIUC in order to have the actual advantages of Facets one has to
> >>>> "connect" it with a TaxonomyWriter
> >>>>
> >>>> FacetsConfig config = new FacetsConfig();
> >>>> DirectoryTaxonomyWriter taxoWriter = new
> >> DirectoryTaxonomyWriter(taxoDir);
> >>>> indexWriter.addDocument(config.build(taxoWriter, doc));
> >>>>
> >>>> right?
> >>>>
> >>>> Thanks
> >>>>
> >>>> Michael
> >>>>
> >>>>
> >>>>
> >>>>
> >>>> Am 20.10.23 um 12:19 schrieb Michael McCandless:
> >>>>> There are some differences.
> >>>>>
> >>>>> StringField is indexed into the inverted index (postings) so you can
> do
> >>>>> efficient filtering. You can also store in stored fields to
> retrieve.
> >>>>>
> >>>>> FacetField does everything StringField does (filtering, storing
> >>>> (maybe?)),
> >>>>> but in addition it stores data for faceting. I.e. you can compute
> >> facet
> >>>>> counts or simple aggregations at search time.
> >>>>>
> >>>>> FacetField is also hierarchical: you can filter and facet by
> different
> >>>>> points/levels of your hierarchy.
> >>>>>
> >>>>> Mike McCandless
> >>>>>
> >>>>> http://blog.mikemccandless.com
> >>>>>
> >>>>>
> >>>>> On Fri, Oct 20, 2023 at 5:43?AM Michael Wechner <
> >>>> michael.wechner@wyona.com>
> >>>>> wrote:
> >>>>>
> >>>>>> Hi
> >>>>>>
> >>>>>> I have found the following simple Facet Example
> >>>>>>
> >>>>>>
> >>>>>>
> >>
> https://github.com/apache/lucene/blob/main/lucene/demo/src/java/org/apache/lucene/demo/facet/SimpleFacetsExample.java
> >>>>>> whereas for a simple categorization of documents I currently use
> >>>>>> StringField, e.g.
> >>>>>>
> >>>>>> doc1.add(new StringField("category", "book"));
> >>>>>> doc1.add(new StringField("category", "quantum_physics"));
> >>>>>> doc1.add(new StringField("category", "Neumann"))
> >>>>>> doc1.add(new StringField("category", "Wheeler"))
> >>>>>>
> >>>>>> doc2.add(new StringField("category", "magazine"));
> >>>>>> doc2.add(new StringField("category", "astro_physics"));
> >>>>>>
> >>>>>> which works well, but would it be better to use Facets for this,
> e.g.
> >>>>>>
> >>>>>> doc1.add(new FacetField("media-type", "book"));
> >>>>>> doc1.add(new FacetField("topic", "physics", "quantum");
> >>>>>> doc1.add(new FacetField("author", "Neumann");
> >>>>>> doc1.add(new FacetField("author", "Wheeler");
> >>>>>>
> >>>>>> doc1.add(new FacetField("media-type", "magazine"));
> >>>>>> doc1.add(new FacetField("topic", "physics", "astro");
> >>>>>>
> >>>>>> ?
> >>>>>>
> >>>>>> IIUC the StringField approach is more general, whereas the
> FacetField
> >>>>>> approach allows to do a more specific categorization / search.
> >>>>>> Or do I misunderstand this?
> >>>>>>
> >>>>>> Thanks
> >>>>>>
> >>>>>> Michael
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
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