Package org.apache.lucene.util.hnsw

Class HnswGraphSearcher

java.lang.Object

org.apache.lucene.util.hnsw.HnswGraphSearcher

Direct Known Subclasses:

FilteredHnswGraphSearcher

public class HnswGraphSearcher
extends Object

Searches an HNSW graph to find nearest neighbors to a query vector. For more background on the search algorithm, see HnswGraph.

Field Summary

Fields

Modifier and Type	Field	Description
protected final NeighborQueue	candidates	Scratch data structures that are used in each searchLevel(org.apache.lucene.util.hnsw.RandomVectorScorer, int, int, int[], org.apache.lucene.util.hnsw.HnswGraph) call.
protected BitSet	visited

Constructor Summary

Constructors

Constructor	Description
HnswGraphSearcher(NeighborQueue candidates, BitSet visited)	Creates a new graph searcher.

Method Summary

Modifier and Type	Method	Description
void	search(KnnCollector results, RandomVectorScorer scorer, HnswGraph graph, Bits acceptOrds)	Search the graph for the given scorer.
static KnnCollector	search(RandomVectorScorer scorer, int topK, OnHeapHnswGraph graph, Bits acceptOrds, int visitedLimit)	Search OnHeapHnswGraph, this method is thread safe.
static void	search(RandomVectorScorer scorer, KnnCollector knnCollector, HnswGraph graph, Bits acceptOrds)	See search(RandomVectorScorer, KnnCollector, HnswGraph, Bits, int)
static void	search(RandomVectorScorer scorer, KnnCollector knnCollector, HnswGraph graph, Bits acceptOrds, int filteredDocCount)	Searches the HNSW graph for the nearest neighbors of a query vector.
HnswGraphBuilder.GraphBuilderKnnCollector	searchLevel(RandomVectorScorer scorer, int topK, int level, int[] eps, HnswGraph graph)	Searches for the nearest neighbors of a query vector in a given level.

Methods inherited from class java.lang.Object

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

Field Details

candidates

protected final NeighborQueue candidates

Scratch data structures that are used in each searchLevel(org.apache.lucene.util.hnsw.RandomVectorScorer, int, int, int[], org.apache.lucene.util.hnsw.HnswGraph) call. These can be expensive to allocate, so they're cleared and reused across calls.

visited

protected BitSet visited

Constructor Details

HnswGraphSearcher

public HnswGraphSearcher(NeighborQueue candidates,
 BitSet visited)

Creates a new graph searcher.

Parameters:

candidates - max heap that will track the candidate nodes to explore

visited - bit set that will track nodes that have already been visited

Method Details

search

public static void search(RandomVectorScorer scorer,
 KnnCollector knnCollector,
 HnswGraph graph,
 Bits acceptOrds)
                   throws IOException

See search(RandomVectorScorer, KnnCollector, HnswGraph, Bits, int)

Parameters:

scorer - the scorer to compare the query with the nodes

knnCollector - a hnsw knn collector of top knn results to be returned

graph - the graph values. May represent the entire graph, or a level in a hierarchical graph.

acceptOrds - Bits that represents the allowed document ordinals to match, or null if they are all allowed to match.

Throws:

IOException

search

public static void search(RandomVectorScorer scorer,
 KnnCollector knnCollector,
 HnswGraph graph,
 Bits acceptOrds,
 int filteredDocCount)
                   throws IOException

Searches the HNSW graph for the nearest neighbors of a query vector. If entry points are directly provided via the knnCollector, then the search will be initialized at those points. Otherwise, the search will discover the best entry point per the normal HNSW search algorithm.

Parameters:

scorer - the scorer to compare the query with the nodes

knnCollector - a hnsw knn collector of top knn results to be returned

graph - the graph values. May represent the entire graph, or a level in a hierarchical graph.

acceptOrds - Bits that represents the allowed document ordinals to match, or null if they are all allowed to match.

filteredDocCount - the number of docs that pass the filter

Throws:

IOException

search

public static KnnCollector search(RandomVectorScorer scorer,
 int topK,
 OnHeapHnswGraph graph,
 Bits acceptOrds,
 int visitedLimit)
                           throws IOException

Search OnHeapHnswGraph, this method is thread safe.

Parameters:

scorer - the scorer to compare the query with the nodes

topK - the number of nodes to be returned

graph - the graph values. May represent the entire graph, or a level in a hierarchical graph.

acceptOrds - Bits that represents the allowed document ordinals to match, or null if they are all allowed to match.

visitedLimit - the maximum number of nodes that the search is allowed to visit

Returns:

a set of collected vectors holding the nearest neighbors found

Throws:

IOException

searchLevel

public HnswGraphBuilder.GraphBuilderKnnCollector searchLevel(RandomVectorScorer scorer,
 int topK,
 int level,
 int[] eps,
 HnswGraph graph)
                                                      throws IOException

Searches for the nearest neighbors of a query vector in a given level.

If the search stops early because it reaches the visited nodes limit, then the results will be marked incomplete through NeighborQueue.incomplete().

Parameters:

scorer - the scorer to compare the query with the nodes

topK - the number of nearest to query results to return

level - level to search

eps - the entry points for search at this level expressed as level 0th ordinals

graph - the graph values

Returns:

a set of collected vectors holding the nearest neighbors found

Throws:

IOException

search

public void search(KnnCollector results,
 RandomVectorScorer scorer,
 HnswGraph graph,
 Bits acceptOrds)
            throws IOException

Search the graph for the given scorer. Gathering results in the provided collector that pass the provided acceptOrds.

Parameters:

results - the collector to collect the results

scorer - the scorer to compare the query with the nodes

graph - the HNSWGraph

acceptOrds - the ordinals to accept for the results

Throws:

IOException - When accessing the vectors or graph fails