[GitHub] [lucene] msokolov commented on a change in pull request #262: LUCENE-10063: implement SimpleTextKnnvectorsReader.search

[GitBox <gi...@apache.org>]

msokolov commented on a change in pull request #262:
URL: https://github.com/apache/lucene/pull/262#discussion_r696706087



##########
File path: lucene/codecs/src/java/org/apache/lucene/codecs/simpletext/SimpleTextKnnVectorsReader.java
##########
@@ -140,7 +147,38 @@ public VectorValues getVectorValues(String field) throws IOException {
 
   @Override
   public TopDocs search(String field, float[] target, int k, Bits acceptDocs) throws IOException {
-    throw new UnsupportedOperationException();
+    VectorValues values = getVectorValues(field);

Review comment:
       Thanks, let's follow the convention of relying on callers to do such checking then.

##########
File path: lucene/codecs/src/java/org/apache/lucene/codecs/simpletext/SimpleTextKnnVectorsReader.java
##########
@@ -140,7 +147,38 @@ public VectorValues getVectorValues(String field) throws IOException {
 
   @Override
   public TopDocs search(String field, float[] target, int k, Bits acceptDocs) throws IOException {
-    throw new UnsupportedOperationException();
+    VectorValues values = getVectorValues(field);
+    if (values == null) {
+      return null;
+    }
+    if (target.length != values.dimension()) {
+      throw new IllegalArgumentException(
+          "incorrect dimension for field "
+              + field
+              + "; expected "
+              + values.dimension()
+              + " but target has "
+              + target.length);
+    }
+    FieldInfo info = readState.fieldInfos.fieldInfo(field);
+    VectorSimilarityFunction vectorSimilarity = info.getVectorSimilarityFunction();
+    HitQueue topK = new HitQueue(k, false);
+    int doc;
+    while ((doc = values.nextDoc()) != DocIdSetIterator.NO_MORE_DOCS) {
+      float[] vector = values.vectorValue();
+      float score = vectorSimilarity.compare(vector, target);
+      if (vectorSimilarity.reversed) {
+        score = 1 / (score + 1);
+      }
+      topK.insertWithOverflow(new ScoreDoc(doc, score));
+    }
+    ScoreDoc[] topScoreDocs = new ScoreDoc[topK.size()];
+    int i = 0;
+    for (ScoreDoc scoreDoc : topK) {
+      topScoreDocs[i++] = scoreDoc;
+    }
+    Arrays.sort(topScoreDocs, Comparator.comparingInt(x -> x.doc));

Review comment:
       No, that's exactly right - should be sorted by score here, not by docid - I was confused having just written the Query implementation. I do see the `KnnVectorsReader` javadoc doesn't explicitly state what the contract is supposed to be; let's rectify that in a separate issue.




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