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From Chitra R <>
Subject Re: Faceting : what are the limitations of Taxonomy (Separate index and hierarchical facets) and SortedSetDocValuesFacetField ( flat facets and no sidecar index) ?
Date Fri, 11 Nov 2016 10:21:00 GMT
Hi Shai,

        i)Hope, when opening SortedSetDocValuesReaderState , we are
calculating ordinals( this will be used to calculate facet count ) for doc
values field and this only made the state instance somewhat costly.
                      Am I right or any other reason behind that?

         ii) During indexing, we are providing facet ordinals in each doc
and I think it will be useful in search side, to calculate facet counts
only for matching docs.  otherwise, it carries any other benefits?

         iii) Is SortedSetDocValuesReaderState thread-safe (ie) multiple
threads can call this method concurrently?

Kindly post your suggestions.



On Thu, Nov 10, 2016 at 4:34 PM, Shai Erera <> wrote:

> Hi
> The reason IMO is historic - ES and Solr had faceting solutions before
> Lucene had it. There were discussions in the past about using the Lucene
> faceting module in Solr (can't tell for ES) but, sadly, I can't say I see
> it happening at this point.
> Regarding your other question, IMO the Lucene faceting engine, in terms of
> performance and customizability, is on par with Solr/ES. However, it lacks
> distributed faceting support and aggregations. Since many people use
> Solr/ES and not Lucene directly, the Solr/ES faceting module continues to
> advance separately from the Lucene one.
> Enhancing Lucene facets with aggregations and even distributed faceting
> capabilities is mostly a matter of time and priorities. If you're
> interested in it, I'd be willing to collaborate with you on that as much as
> I can!
> And I'd still hope that this work finds its way into Solr/ES, as I think
> it's silly to have that many number of faceting implementations, where they
> all rely on the same low-level data structure - Lucene!
> Shai
> On Thu, Nov 10, 2016 at 12:32 PM Kumaran Ramasubramanian <
> wrote:
> > Hi All,
> >             We all know that Lucene supports faceting by providing
> > Taxonomy(Separate index and hierarchical facets) and
> > SortedSetDocValuesFacetField ( flat facets and no sidecar index).
> >
> >       Then why did solr and elastic search go for its own implementation
> ?
> >  ( that is, solr uses block join & elasticsearch uses aggregations ) Is
> > there any limitations in lucene's implementation ?
> >
> >
> > --
> > Kumaran R
> >

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