Package org.apache.lucene.spatial.prefix

# Class PrefixTreeFacetCounter

java.lang.Object
org.apache.lucene.spatial.prefix.PrefixTreeFacetCounter

public class PrefixTreeFacetCounter extends Object
Computes facets on cells for `PrefixTreeStrategy`.

NOTE: If for a given document and a given field using `RecursivePrefixTreeStrategy` multiple values are indexed (i.e. multi-valued) and at least one of them is a non-point, then there is a possibility of double-counting the document in the facet results. Since each shape is independently turned into grid cells at a resolution chosen by the shape's size, it's possible they will be indexed at different resolutions. This means the document could be present in BOTH the postings for a cell in both its prefix and leaf variants. To avoid this, use a single valued field with a `ShapeCollection` (or WKT equivalent). Or calculate a suitable level/distErr to index both and call `PrefixTreeStrategy.createIndexableFields(org.locationtech.spatial4j.shape.Shape, int)` with the same value for all shapes for a given document/field.

WARNING: This API is experimental and might change in incompatible ways in the next release.

## Nested Class Summary

Nested Classes
Modifier and Type
Class
Description
`static class`
`PrefixTreeFacetCounter.FacetVisitor`
A callback/visitor of facet counts.

## Method Summary

Modifier and Type
Method
Description
`static void`
`compute(PrefixTreeStrategy strategy, IndexReaderContext context, Bits topAcceptDocs, org.locationtech.spatial4j.shape.Shape queryShape, int facetLevel, PrefixTreeFacetCounter.FacetVisitor facetVisitor)`
Computes facets using a callback/visitor style design, allowing flexibility for the caller to determine what to do with each underlying count.
`static void`
`compute(PrefixTreeStrategy strategy, LeafReaderContext context, Bits acceptDocs, org.locationtech.spatial4j.shape.Shape queryShape, int facetLevel, PrefixTreeFacetCounter.FacetVisitor facetVisitor)`
Lower-level per-leaf segment method.

### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

## Method Details

### compute

public static void compute(PrefixTreeStrategy strategy, IndexReaderContext context, Bits topAcceptDocs, org.locationtech.spatial4j.shape.Shape queryShape, int facetLevel, PrefixTreeFacetCounter.FacetVisitor facetVisitor) throws IOException
Computes facets using a callback/visitor style design, allowing flexibility for the caller to determine what to do with each underlying count.

Parameters:
  `strategy` - the prefix tree strategy (contains the field reference, grid, max levels)
  `context` - the IndexReader's context
  `topAcceptDocs` - a Bits to limit counted docs. If null, live docs are counted.
  `queryShape` - the shape to limit the range of facet counts to
  `facetLevel` - the maximum depth (detail) of faceted cells
  `facetVisitor` - the visitor/callback to receive the counts
Throws:
  `IOException`

### compute

public static void compute(PrefixTreeStrategy strategy, LeafReaderContext context, Bits acceptDocs, org.locationtech.spatial4j.shape.Shape queryShape, int facetLevel, PrefixTreeFacetCounter.FacetVisitor facetVisitor) throws IOException
Lower-level per-leaf segment method.

Throws:
  `IOException`