Fix NPE in flat_bbq scorer when all vectors are missing

Author: benwtrent

server/src/main/java/org/elasticsearch/index/codec/vectors/es816/ES816BinaryFlatVectorsScorer.java

@@ -59,6 +59,9 @@ public RandomVectorScorer getRandomVectorScorer(
         float[] target
     ) throws IOException {
         if (vectorValues instanceof BinarizedByteVectorValues binarizedVectors) {
+            assert binarizedVectors.getQuantizer() != null
+                : "BinarizedByteVectorValues must have a quantizer for ES816BinaryFlatVectorsScorer";
+            assert binarizedVectors.size() > 0 : "BinarizedByteVectorValues must have at least one vector for ES816BinaryFlatVectorsScorer";
             BinaryQuantizer quantizer = binarizedVectors.getQuantizer();
             float[] centroid = binarizedVectors.getCentroid();
             // FIXME: precompute this once?

server/src/main/java/org/elasticsearch/index/codec/vectors/es816/ES816BinaryQuantizedVectorsReader.java

@@ -160,7 +160,7 @@ static void validateFieldEntry(FieldInfo info, FieldEntry fieldEntry) {
     @Override
     public RandomVectorScorer getRandomVectorScorer(String field, float[] target) throws IOException {
         FieldEntry fi = fields.get(field);
-        if (fi == null) {
+        if (fi == null || fi.size() == 0) {
             return null;
         }
         return vectorScorer.getRandomVectorScorer(

server/src/main/java/org/elasticsearch/index/codec/vectors/es818/ES818BinaryFlatVectorsScorer.java

@@ -66,6 +66,9 @@ public RandomVectorScorer getRandomVectorScorer(
         float[] target
     ) throws IOException {
         if (vectorValues instanceof BinarizedByteVectorValues binarizedVectors) {
+            assert binarizedVectors.getQuantizer() != null
+                : "BinarizedByteVectorValues must have a quantizer for ES816BinaryFlatVectorsScorer";
+            assert binarizedVectors.size() > 0 : "BinarizedByteVectorValues must have at least one vector for ES816BinaryFlatVectorsScorer";
             OptimizedScalarQuantizer quantizer = binarizedVectors.getQuantizer();
             float[] centroid = binarizedVectors.getCentroid();
             // We make a copy as the quantization process mutates the input

server/src/main/java/org/elasticsearch/index/codec/vectors/es818/ES818BinaryQuantizedVectorsReader.java

@@ -160,7 +160,7 @@ static void validateFieldEntry(FieldInfo info, FieldEntry fieldEntry) {
     @Override
     public RandomVectorScorer getRandomVectorScorer(String field, float[] target) throws IOException {
         FieldEntry fi = fields.get(field);
-        if (fi == null) {
+        if (fi == null || fi.size() == 0) {
             return null;
         }
         return vectorScorer.getRandomVectorScorer(