Lucene.NET with simplified (and correct!) facet behaviour
What is this? Well, to me correct facet behaviour is for each facet "group" to exclude selections concerning itself from the calculation of facets.
Stolen from the documentation of SOLR - here is what I mean:
To implement a multi-select facet for doctype, a GUI may want to still display the other doctype values and their associated counts, as if the doctype:pdf constraint had not yet been applied. Example:
=== Document Type === [ ] Word (42) [x] PDF (96) [ ] Excel(11) [ ] HTML (63)
In short this library gives you a derived searcher class, FacetSearcher
[TestMethod]
public void DrilldownMultiFacetsShouldReturnCorrectFacetsAndDocuments()
{
var _target = new FacetSearcher(SetupIndex());
var actual = _target.SearchWithFacets(new MatchAllDocsQuery(), 100, new List<SelectedFacet>
{
new SelectedFacet{ FieldName = "color", SelectedValues = new List<string>{"yellow"}},
new SelectedFacet{ FieldName = "type", SelectedValues = new List<string>{"fruit"}}
}, new[] { "color", "type" });
var colorFacets = actual.Facets.Where(x => x.FacetFieldName == "color").ToList();
var typeFacets = actual.Facets.Where(x => x.FacetFieldName == "type").ToList();
Assert.AreEqual(2, actual.Hits.TotalHits);
Assert.AreEqual(1, colorFacets.Count);
Assert.AreEqual(3, typeFacets.Count);
Assert.AreEqual(2, colorFacets.Single(x => x.Value == "yellow").Count); // only fruits
Assert.AreEqual(1, typeFacets.Single(x => x.Value == "meat").Count); //only yellow
Assert.AreEqual(2, typeFacets.Single(x => x.Value == "fruit").Count);//only yellow
Assert.AreEqual(3, typeFacets.Single(x => x.Value == "food").Count);//only yellow
}
protected static IndexReader SetupIndex()
{
var directory = new RAMDirectory();
var writer = new IndexWriter(directory, new StandardAnalyzer(Lucene.Net.Util.Version.LUCENE_30), true,
IndexWriter.MaxFieldLength.LIMITED);
writer.AddDocument(new Document()
.AddField("title", "Banana", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("color", "yellow", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("type", "food", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("type", "fruit", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("keywords", "apa hello whatever", Field.Store.YES, Field.Index.ANALYZED)
.AddField("price", "10", Field.Store.YES, Field.Index.NOT_ANALYZED));
writer.AddDocument(new Document()
.AddField("title", "Apple", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("color", "yellow", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("type", "food", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("type", "fruit", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("price", "20", Field.Store.YES, Field.Index.NOT_ANALYZED));
writer.AddDocument(new Document()
.AddField("title", "Burger", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("color", "yellow", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("type", "food", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("type", "meat", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("price", "30", Field.Store.YES, Field.Index.NOT_ANALYZED));
writer.AddDocument(new Document()
.AddField("title", "Milk", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("color", "white", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("type", "drink", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("price", "40", Field.Store.YES, Field.Index.NOT_ANALYZED));
writer.AddDocument(new Document()
.AddField("title", "Water", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("color", "none", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("type", "drink", Field.Store.YES, Field.Index.NOT_ANALYZED)
.AddField("keywords", "apa hello cars", Field.Store.YES, Field.Index.ANALYZED)
.AddField("price", "0", Field.Store.YES, Field.Index.NOT_ANALYZED));
writer.Flush(true, true, true);
writer.Optimize();
writer.Commit();
return IndexReader.Open(directory, true);
}
Some more background is available at http://www.stefanholmberg.com/post/2014/06/05/Lucenenet-and-multiple-facets
http://aviationquestions.aircraftdata.net/search/aviation
Here you get right into the search for "aviation". See to the right, User and Tags are facet values. Now, when clicking one of the users, search result is indeed filtered - but as you can see you can still select more users. I.e possible to multi value facetting!