Lucene: facet range depends on the returned results - lucene

Question

I have a working search set up where I give the facet range, and get the correct results back.
The problem is that for prices facet, I need to be depending on the returned result, so I can't know the ranges beforehand.
Example 1: the search found 4 products with the following prices: 20, 30, 40, 55. So I expect the facets be something like this:
0 - 20 (1)
21 - 40 (2)
41 - 60 (1)
Example 2: the search found 2 products with the following prices: 200, 400, So I expect the facets be something like this:
100 - 200 (1)
300 - 400 (1)
Is there somewhere in Lucene where I can specify that I want the ranges be based on a field from the search results?
Thank you

Answer 1

After many searching I did not find a way to do it out of the box.
The way to do it, is to extend DrillSideways, and at the beginning of the BuildFacetsResult method, we extract the field with the necessary value. Something like this:
public class DrillSidewaysHelper : DrillSideways
{
private TopFieldCollector _localCollector;
private List<decimal> _prices;
protected override LuceneFacets BuildFacetsResult(FacetsCollector drillDownCollector, FacetsCollector[] drillSidewaysCollectors,
string[] drillSidewaysFacets)
{
ExtractResults(); //here we extract the methods from the _localCollector and populate _prices
....here we can generate the facets range based on the _prices
}
public FacetResultSet<T> OurSearch(DrillDownQuery drillDownQuery, Sort sort)
{
int limit = m_searcher.IndexReader.MaxDoc;
_localCollector = TopFieldCollector.Create(sort, limit, null, true, true, false, true);
var drillSidewaysResult = Search(drillDownQuery, _localCollector);
var facets = ExtractFacets(drillSidewaysResult.Facets);
return new FacetResultSet<T>(_results, (uint) _localCollector.TotalHits, facets);
}
}
and usage:
var drillSideways = new DrillSidewaysHelper(searcher, facetsConfig, taxonomyReader);
return drillSideways.OurSearch(drillDownQuery, sort);