benwtrent commented on code in PR #14963:
URL: https://github.com/apache/lucene/pull/14963#discussion_r2213897171
##########
lucene/core/src/java/org/apache/lucene/codecs/lucene99/Lucene99HnswVectorsFormat.java:
##########
@@ -137,9 +144,16 @@ public final class Lucene99HnswVectorsFormat extends
KnnVectorsFormat {
private final int numMergeWorkers;
private final TaskExecutor mergeExec;
+ /**
+ * Whether to bypass HNSW graph building for tiny segments (below {@link
#HNSW_GRAPH_THRESHOLD}).
+ * When enabled, segments with fewer than the threshold number of vectors
will store only flat
+ * vectors, significantly improving indexing performance for workloads with
frequent flushes.
+ */
+ private final boolean bypassTinySegments;
Review Comment:
If we allow this to be a parameter, it should be a threshold that refers to
the typical `k` used when querying.
##########
lucene/core/src/java/org/apache/lucene/codecs/lucene99/Lucene99HnswVectorsReader.java:
##########
@@ -326,16 +335,19 @@ private void search(
final KnnCollector collector =
new OrdinalTranslatedKnnCollector(knnCollector, scorer::ordToDoc);
final Bits acceptedOrds = scorer.getAcceptOrds(acceptDocs);
- HnswGraph graph = getGraph(fieldEntry);
- boolean doHnsw = knnCollector.k() < scorer.maxOrd();
+ boolean doHnsw =
+ knnCollector.k() < scorer.maxOrd()
+ && (bypassTinySegments == false
+ || fieldEntry.size() >
Lucene99HnswVectorsFormat.HNSW_GRAPH_THRESHOLD);
Review Comment:
The reader should just look to see if there is a graph.
##########
lucene/core/src/java/org/apache/lucene/codecs/lucene99/Lucene99HnswVectorsWriter.java:
##########
@@ -632,8 +695,23 @@ public void addValue(int docID, T vectorValue) throws
IOException {
+ "\" appears more than once in this document (only one value
is allowed per field)");
}
flatFieldVectorsWriter.addValue(docID, vectorValue);
- scorer.setScoringOrdinal(node);
- hnswGraphBuilder.addGraphNode(node, scorer);
+ // Check if we need to initialize graph builder for tiny segment
optimization
+ if (bypassTinySegments
+ && graphBuilderInitialized == false
+ && node >= Lucene99HnswVectorsFormat.HNSW_GRAPH_THRESHOLD) {
Review Comment:
I am thinking we should just use the `expectedNodeVisited` logic for the
given node count (treating like its a "graph") vs. the tiny segment threshold
number (which should be used as a `k`).
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