iprithv commented on code in PR #16271:
URL: https://github.com/apache/lucene/pull/16271#discussion_r3444262064
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lucene/core/src/java/org/apache/lucene/search/AbstractKnnVectorQuery.java:
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@@ -149,9 +149,64 @@ public Query rewrite(IndexSearcher indexSearcher) throws
IOException {
topK = runSearchTasks(tasks, taskExecutor, perLeafResults,
leafReaderContexts);
}
if (topK.scoreDocs.length == 0) {
- return MatchNoDocsQuery.INSTANCE;
+ return new MatchNoDocsQuery("No documents matched the nearest-neighbor
search");
}
- return DocAndScoreQuery.createDocAndScoreQuery(reader, topK, reentryCount);
+ return DocAndScoreQuery.createDocAndScoreQuery(
+ reader, topK, reentryCount, noMatchExplainer(topK, filterWeight));
+ }
+
+ /** Builds the explainer for documents this query did not collect, capturing
minTopKScore. */
+ private DocAndScoreQuery.NoMatchExplainer noMatchExplainer(TopDocs topK,
Weight filterWeight) {
+ // topK is score-descending, so the lowest collected score is the last
entry.
+ final float minTopKScore = topK.scoreDocs[topK.scoreDocs.length - 1].score;
+ return (context, doc, topN) ->
+ explainNotCollected(context, doc, topN, filterWeight, minTopKScore);
Review Comment:
filterWeight here was created during rewrite() against a specific reader.
But explain() can be called later with a different reader. when that happens,
filterWeight.scorer(context) gets a LeafReaderContext it wasn't built for,
which could blow up.
match side is fine since scores/docs are already materialized in the array.
but this no-match path re-evaluates the filter live, so it has this
stale-reader risk.
can you add a try/catch around the filter check.
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