Module org.apache.lucene.join

Package org.apache.lucene.search.join

Class DiversifyingNearestChildrenKnnCollector

java.lang.Object

org.apache.lucene.search.AbstractKnnCollector

org.apache.lucene.search.join.DiversifyingNearestChildrenKnnCollector

All Implemented Interfaces:

KnnCollector

class DiversifyingNearestChildrenKnnCollector
extends AbstractKnnCollector

This collects the nearest children vectors. Diversifying the results over the provided parent filter. This means the nearest children vectors are returned, but only one per parent

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static class	DiversifyingNearestChildrenKnnCollector.NodeIdCachingHeap	This is a minimum binary heap, inspired by LongHeap.
private static class	DiversifyingNearestChildrenKnnCollector.ParentChildScore	Keeps track of child node, parent node, and the stored score.

Field Summary

Fields

Modifier and Type	Field	Description
private final DiversifyingNearestChildrenKnnCollector.NodeIdCachingHeap	heap
private final BitSet	parentBitSet

Fields inherited from class org.apache.lucene.search.AbstractKnnCollector

visitedCount

Constructor Summary

Constructors

Constructor	Description
DiversifyingNearestChildrenKnnCollector(int k, int visitLimit, BitSet parentBitSet)	Create a new object for joining nearest child kNN documents with a parent bitset

Method Summary

Modifier and Type	Method	Description
boolean	collect(int docId, float nodeScore)	If the heap is not full (size is less than the initialSize provided to the constructor), adds a new node-and-score element.
float	minCompetitiveSimilarity()	This method is utilized during search to ensure only competitive results are explored.
int	numCollected()
TopDocs	topDocs()	This drains the collected nearest kNN results and returns them in a new TopDocs collection, ordered by score descending.
String	toString()

Methods inherited from class org.apache.lucene.search.AbstractKnnCollector

earlyTerminated, incVisitedCount, k, visitedCount, visitLimit

Methods inherited from class java.lang.Object

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

Field Details

parentBitSet

private final BitSet parentBitSet

heap

private final DiversifyingNearestChildrenKnnCollector.NodeIdCachingHeap heap

Constructor Details

DiversifyingNearestChildrenKnnCollector

public DiversifyingNearestChildrenKnnCollector(int k,
 int visitLimit,
 BitSet parentBitSet)

Create a new object for joining nearest child kNN documents with a parent bitset

Parameters:

k - The number of joined parent documents to collect

visitLimit - how many child vectors can be visited

parentBitSet - The leaf parent bitset

Method Details

collect

public boolean collect(int docId,
 float nodeScore)

If the heap is not full (size is less than the initialSize provided to the constructor), adds a new node-and-score element. If the heap is full, compares the score against the current top score, and replaces the top element if newScore is better than (greater than unless the heap is reversed), the current top score.

If docId's parent node has previously been collected and the provided nodeScore is less than the stored score it will not be collected.

Specified by:

collect in interface KnnCollector

Specified by:

collect in class AbstractKnnCollector

Parameters:

docId - the neighbor docId

nodeScore - the score of the neighbor, relative to some other node

Returns:

true if the vector is collected

minCompetitiveSimilarity

public float minCompetitiveSimilarity()

Description copied from interface: KnnCollector

This method is utilized during search to ensure only competitive results are explored.

Consequently, if this results collector wants to collect `k` results, this should return Float.NEGATIVE_INFINITY when not full.

When full, the minimum score should be returned.

Specified by:

minCompetitiveSimilarity in interface KnnCollector

Specified by:

minCompetitiveSimilarity in class AbstractKnnCollector

Returns:

the current minimum competitive similarity in the collection

toString

public String toString()

Overrides:

toString in class Object

topDocs

public TopDocs topDocs()

Description copied from interface: KnnCollector

This drains the collected nearest kNN results and returns them in a new TopDocs collection, ordered by score descending. NOTE: This is generally a destructive action and the collector should not be used after topDocs() is called.

Specified by:

topDocs in interface KnnCollector

Specified by:

topDocs in class AbstractKnnCollector

Returns:

The collected top documents

numCollected

public int numCollected()

Specified by:

numCollected in class AbstractKnnCollector