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Use TernaryLongHeap in NeighborQueue for faster vector search performance #15163

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merged 1 commit into from
Sep 10, 2025
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Use TernaryLongHeap in NeighborQueue for faster vector search performance #15163

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2 changes: 2 additions & 0 deletions lucene/CHANGES.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -129,6 +129,8 @@ Optimizations
---------------------
* GITHUB#15140: Optimize TopScoreDocCollector with TernaryLongHeap for improved performance over Binary-LongHeap. (Ramakrishna Chilaka)

* GITHUB#15163: Use TernaryLongHeap in NeighborQueue for faster vector search performance. (Ramakrishna Chilaka)

* GITHUB#14998: Speed up flushing of live docs. (Adrien Grand)

Bug Fixes
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12 changes: 6 additions & 6 deletions lucene/core/src/java/org/apache/lucene/util/hnsw/NeighborQueue.java
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Expand Up @@ -17,13 +17,13 @@

package org.apache.lucene.util.hnsw;

import org.apache.lucene.util.LongHeap;
import org.apache.lucene.util.NumericUtils;
import org.apache.lucene.util.TernaryLongHeap;

/**
* NeighborQueue uses a {@link LongHeap} to store lists of arcs in an HNSW graph, represented as a
* neighbor node id with an associated score packed together as a sortable long, which is sorted
* primarily by score. The queue provides both fixed-size and unbounded operations via {@link
* NeighborQueue uses a {@link TernaryLongHeap} to store lists of arcs in an HNSW graph, represented
* as a neighbor node id with an associated score packed together as a sortable long, which is
* sorted primarily by score. The queue provides both fixed-size and unbounded operations via {@link
* #insertWithOverflow(int, float)} and {@link #add(int, float)}, and provides MIN and MAX heap
* subclasses.
*/
Expand All @@ -48,7 +48,7 @@ long apply(long v) {
abstract long apply(long v);
}

private final LongHeap heap;
private final TernaryLongHeap heap;
private final Order order;

// Used to track the number of neighbors visited during a single graph traversal
Expand All @@ -57,7 +57,7 @@ long apply(long v) {
private boolean incomplete;

public NeighborQueue(int initialSize, boolean maxHeap) {
this.heap = new LongHeap(initialSize);
this.heap = new TernaryLongHeap(initialSize);
this.order = maxHeap ? Order.MAX_HEAP : Order.MIN_HEAP;
}

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