[LUCENE-5339] Simplify the facet module APIs

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.7, 6.0
• Component/s: modules/facet
• Lucene Fields: New
• Assignee: Michael McCandless
• Reporter: Michael McCandless
• Created: 12/Nov/13 23:05
• Updated: 28/Aug/22 13:56
• Resolved: 04/Jan/14 12:33

Description

I'd like to explore simplifications to the facet module's APIs: I
think the current APIs are complex, and the addition of a new feature
(sparse faceting, LUCENE-5333) threatens to add even more classes
(e.g., FacetRequestBuilder). I think we can do better.

So, I've been prototyping some drastic changes; this is very
early/exploratory and I'm not sure where it'll wind up but I think the
new approach shows promise.

The big changes are:

• Instead of *FacetRequest/Params/Result, you directly instantiate
  the classes that do facet counting (currently TaxonomyFacetCounts,
  RangeFacetCounts or SortedSetDVFacetCounts), passing in the
  SimpleFacetsCollector, and then you interact with those classes to
  pull labels + values (topN under a path, sparse, specific labels).

• At index time, no more FacetIndexingParams/CategoryListParams;
  instead, you make a new SimpleFacetFields and pass it the field it
  should store facets + drill downs under. If you want more than
  one CLI you create more than one instance of SimpleFacetFields.

• I added a simple schema, where you state which dimensions are
  hierarchical or multi-valued. From this we decide how to index
  the ordinals (no more OrdinalPolicy).

Sparse faceting is just another method (getAllDims), on both taxonomy
& ssdv facet classes.

I haven't created a common base class / interface for all of the
search-time facet classes, but I think this may be possible/clean, and
perhaps useful for drill sideways.

All the new classes are under oal.facet.simple.*.

Lots of things that don't work yet: drill sideways, complements,
associations, sampling, partitions, etc. This is just a start ...

Issue Links

• contains: LUCENE-5367 NoSuchElementException occurs when org.apache.lucene.facet.index.FacetFields is used.