Add vector search support for fields in nested objects

src/main/java/com/yelp/nrtsearch/server/field/VectorFieldDef.java

@@ -25,6 +25,8 @@
 import com.yelp.nrtsearch.server.grpc.Field;
 import com.yelp.nrtsearch.server.grpc.KnnQuery;
 import com.yelp.nrtsearch.server.grpc.VectorIndexingOptions;
+import com.yelp.nrtsearch.server.query.vector.NrtDiversifyingChildrenByteKnnVectorQuery;
+import com.yelp.nrtsearch.server.query.vector.NrtDiversifyingChildrenFloatKnnVectorQuery;
 import com.yelp.nrtsearch.server.query.vector.NrtKnnByteVectorQuery;
 import com.yelp.nrtsearch.server.query.vector.NrtKnnFloatVectorQuery;
 import com.yelp.nrtsearch.server.vector.ByteVectorType;
@@ -51,6 +53,7 @@
 import org.apache.lucene.index.SegmentWriteState;
 import org.apache.lucene.index.VectorSimilarityFunction;
 import org.apache.lucene.search.Query;
+import org.apache.lucene.search.join.BitSetProducer;
 import org.apache.lucene.util.BytesRef;
 import org.apache.lucene.util.VectorUtil;
 
@@ -113,9 +116,15 @@ enum VectorSearchType {
    * @param k number of nearest neighbors to return
    * @param filterQuery filter query
    * @param numCandidates number of candidates to search per segment
+   * @param parentBitSetProducer parent bit set producer for searching nested fields, or null
    * @return knn query
    */
-  abstract Query getTypeKnnQuery(KnnQuery knnQuery, int k, Query filterQuery, int numCandidates);
+  abstract Query getTypeKnnQuery(
+      KnnQuery knnQuery,
+      int k,
+      Query filterQuery,
+      int numCandidates,
+      BitSetProducer parentBitSetProducer);
 
   private static VectorSimilarityFunction getSimilarityFunction(String vectorSimilarity) {
     VectorSimilarityFunction similarityFunction = SIMILARITY_FUNCTION_MAP.get(vectorSimilarity);
@@ -307,7 +316,8 @@ public void parseDocumentField(
   }
 
   @Override
-  public Query getKnnQuery(KnnQuery knnQuery, Query filterQuery) {
+  public Query getKnnQuery(
+      KnnQuery knnQuery, Query filterQuery, BitSetProducer parentBitSetProducer) {
     if (!isSearchable()) {
       throw new IllegalArgumentException("Vector field is not searchable: " + getName());
     }
@@ -324,7 +334,7 @@ public Query getKnnQuery(KnnQuery knnQuery, Query filterQuery) {
       throw new IllegalArgumentException("Vector search numCandidates > " + NUM_CANDIDATES_LIMIT);
     }
 
-    return getTypeKnnQuery(knnQuery, k, filterQuery, numCandidates);
+    return getTypeKnnQuery(knnQuery, k, filterQuery, numCandidates, parentBitSetProducer);
   }
 
   /** Field class for 'FLOAT' vector field type. */
@@ -420,7 +430,12 @@ static byte[] convertFloatArrToBytes(float[] floatArr) {
     }
 
     @Override
-    Query getTypeKnnQuery(KnnQuery knnQuery, int k, Query filterQuery, int numCandidates) {
+    Query getTypeKnnQuery(
+        KnnQuery knnQuery,
+        int k,
+        Query filterQuery,
+        int numCandidates,
+        BitSetProducer parentBitSetProducer) {
       if (knnQuery.getQueryVectorCount() != getVectorDimensions()) {
         throw new IllegalArgumentException(
             "Invalid query vector size, expected: "
@@ -433,7 +448,12 @@ Query getTypeKnnQuery(KnnQuery knnQuery, int k, Query filterQuery, int numCandid
         queryVector[i] = knnQuery.getQueryVector(i);
       }
       validateVectorForSearch(queryVector);
-      return new NrtKnnFloatVectorQuery(getName(), queryVector, k, filterQuery, numCandidates);
+      if (parentBitSetProducer != null) {
+        return new NrtDiversifyingChildrenFloatKnnVectorQuery(
+            getName(), queryVector, filterQuery, k, numCandidates, parentBitSetProducer);
+      } else {
+        return new NrtKnnFloatVectorQuery(getName(), queryVector, k, filterQuery, numCandidates);
+      }
     }
 
     /**
@@ -560,7 +580,12 @@ byte[] parseVectorFieldToByteArr(String fieldValueJson) {
     }
 
     @Override
-    Query getTypeKnnQuery(KnnQuery knnQuery, int k, Query filterQuery, int numCandidates) {
+    Query getTypeKnnQuery(
+        KnnQuery knnQuery,
+        int k,
+        Query filterQuery,
+        int numCandidates,
+        BitSetProducer parentBitSetProducer) {
       if (knnQuery.getQueryByteVector().size() != getVectorDimensions()) {
         throw new IllegalArgumentException(
             "Invalid query byte vector size, expected: "
@@ -570,7 +595,12 @@ Query getTypeKnnQuery(KnnQuery knnQuery, int k, Query filterQuery, int numCandid
       }
       byte[] queryVector = knnQuery.getQueryByteVector().toByteArray();
       validateVectorForSearch(queryVector);
-      return new NrtKnnByteVectorQuery(getName(), queryVector, k, filterQuery, numCandidates);
+      if (parentBitSetProducer != null) {
+        return new NrtDiversifyingChildrenByteKnnVectorQuery(
+            getName(), queryVector, filterQuery, k, numCandidates, parentBitSetProducer);
+      } else {
+        return new NrtKnnByteVectorQuery(getName(), queryVector, k, filterQuery, numCandidates);
+      }
     }
 
     /**

src/main/java/com/yelp/nrtsearch/server/field/properties/VectorQueryable.java

@@ -18,6 +18,7 @@
 import com.yelp.nrtsearch.server.field.FieldDef;
 import com.yelp.nrtsearch.server.grpc.KnnQuery;
 import org.apache.lucene.search.Query;
+import org.apache.lucene.search.join.BitSetProducer;
 
 /** Trait interface for {@link FieldDef} types that can be queried by a {@link KnnQuery}. */
 public interface VectorQueryable {
@@ -26,7 +27,9 @@ public interface VectorQueryable {
    *
    * @param knnQuery knn query configuration
    * @param filterQuery query to filter knn search, or null
+   * @param parentBitSetProducer bit set producer for parent documents when searching a nested
+   *     field, or null
    * @return lucene knn query
    */
-  Query getKnnQuery(KnnQuery knnQuery, Query filterQuery);
+  Query getKnnQuery(KnnQuery knnQuery, Query filterQuery, BitSetProducer parentBitSetProducer);
 }

src/main/java/com/yelp/nrtsearch/server/index/IndexState.java

@@ -317,6 +317,30 @@ public String resolveQueryNestedPath(String path) {
     throw new IllegalArgumentException("Nested path is not a nested object field: " + path);
   }
 
+  /**
+   * Get the base path for the nested document containing the field at the given path. For fields in
+   * the base document, this returns _root. The base nested path for _root is null.
+   *
+   * @param path field path
+   * @return nested base path, or null
+   */
+  public static String getFieldBaseNestedPath(String path, IndexState indexState) {
+    Objects.requireNonNull(path, "path cannot be null");
+    if (path.equals(IndexState.ROOT)) {
+      return null;
+    }
+
+    String currentPath = path;
+    while (currentPath.contains(".")) {
+      currentPath = currentPath.substring(0, currentPath.lastIndexOf("."));
+      FieldDef fieldDef = indexState.getFieldOrThrow(currentPath);
+      if (fieldDef instanceof ObjectFieldDef objFieldDef && objFieldDef.isNestedDoc()) {
+        return currentPath;
+      }
+    }
+    return IndexState.ROOT;
+  }
+
   /** Get index state info. */
   public abstract IndexStateInfo getIndexStateInfo();
 

src/main/java/com/yelp/nrtsearch/server/query/vector/NrtDiversifyingChildrenByteKnnVectorQuery.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2024 Yelp Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.yelp.nrtsearch.server.query.vector;
+
+import org.apache.lucene.search.Query;
+import org.apache.lucene.search.TopDocs;
+import org.apache.lucene.search.TotalHits;
+import org.apache.lucene.search.join.BitSetProducer;
+import org.apache.lucene.search.join.DiversifyingChildrenByteKnnVectorQuery;
+
+/**
+ * A {@link DiversifyingChildrenByteKnnVectorQuery} that has its functionality slightly modified.
+ * The {@link TotalHits} from the vector search are available after the query has been rewritten
+ * using the {@link WithVectorTotalHits} interface. The results merging has also been modified to
+ * produce the top k hits from the top numCandidates hits from each leaf.
+ */
+public class NrtDiversifyingChildrenByteKnnVectorQuery
+    extends DiversifyingChildrenByteKnnVectorQuery implements WithVectorTotalHits {
+  private final int topHits;
+  private TotalHits totalHits;
+
+  public NrtDiversifyingChildrenByteKnnVectorQuery(
+      String field,
+      byte[] target,
+      Query filter,
+      int k,
+      int numCandidates,
+      BitSetProducer parentsFilter) {
+    super(field, target, filter, numCandidates, parentsFilter);
+    this.topHits = k;
+  }
+
+  @Override
+  public TotalHits getTotalHits() {
+    return totalHits;
+  }
+
+  @Override
+  protected TopDocs mergeLeafResults(TopDocs[] perLeafResults) {
+    TopDocs topDocs = TopDocs.merge(topHits, perLeafResults);
+    totalHits = topDocs.totalHits;
+    return topDocs;
+  }
+}

src/main/java/com/yelp/nrtsearch/server/query/vector/NrtDiversifyingChildrenFloatKnnVectorQuery.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2024 Yelp Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.yelp.nrtsearch.server.query.vector;
+
+import org.apache.lucene.search.Query;
+import org.apache.lucene.search.TopDocs;
+import org.apache.lucene.search.TotalHits;
+import org.apache.lucene.search.join.BitSetProducer;
+import org.apache.lucene.search.join.DiversifyingChildrenFloatKnnVectorQuery;
+
+/**
+ * A {@link DiversifyingChildrenFloatKnnVectorQuery} that has its functionality slightly modified.
+ * The {@link TotalHits} from the vector search are available after the query has been rewritten
+ * using the {@link WithVectorTotalHits} interface. The results merging has also been modified to
+ * produce the top k hits from the top numCandidates hits from each leaf.
+ */
+public class NrtDiversifyingChildrenFloatKnnVectorQuery
+    extends DiversifyingChildrenFloatKnnVectorQuery implements WithVectorTotalHits {
+  private final int topHits;
+  private TotalHits totalHits;
+
+  public NrtDiversifyingChildrenFloatKnnVectorQuery(
+      String field,
+      float[] target,
+      Query filter,
+      int k,
+      int numCandidates,
+      BitSetProducer parentsFilter) {
+    super(field, target, filter, numCandidates, parentsFilter);
+    this.topHits = k;
+  }
+
+  @Override
+  public TotalHits getTotalHits() {
+    return totalHits;
+  }
+
+  @Override
+  protected TopDocs mergeLeafResults(TopDocs[] perLeafResults) {
+    TopDocs topDocs = TopDocs.merge(topHits, perLeafResults);
+    totalHits = topDocs.totalHits;
+    return topDocs;
+  }
+}

src/main/java/com/yelp/nrtsearch/server/search/SearchRequestProcessor.java

@@ -76,6 +76,9 @@
 import org.apache.lucene.queryparser.classic.QueryParserBase;
 import org.apache.lucene.queryparser.simple.SimpleQueryParser;
 import org.apache.lucene.search.*;
+import org.apache.lucene.search.join.BitSetProducer;
+import org.apache.lucene.search.join.QueryBitSetProducer;
+import org.apache.lucene.search.join.ToChildBlockJoinQuery;
 import org.apache.lucene.util.QueryBuilder;
 
 /**
@@ -270,13 +273,32 @@ private static Query buildKnnQuery(KnnQuery knnQuery, IndexState indexState) {
       throw new IllegalArgumentException("Field does not support vector search: " + field);
     }
 
+    // Path to nested document containing this field
+    String fieldNestedPath = IndexState.getFieldBaseNestedPath(field, indexState);
+    // Path to parent document, this will be null if the field is in the root document
+    String parentNestedPath = IndexState.getFieldBaseNestedPath(fieldNestedPath, indexState);
+
     Query filterQuery;
     if (knnQuery.hasFilter()) {
       filterQuery = QueryNodeMapper.getInstance().getQuery(knnQuery.getFilter(), indexState);
     } else {
       filterQuery = null;
     }
-    return vectorQueryable.getKnnQuery(knnQuery, filterQuery);
+
+    BitSetProducer parentBitSetProducer = null;
+    if (parentNestedPath != null) {
+      Query parentQuery =
+          QueryNodeMapper.getInstance().getNestedPathQuery(indexState, parentNestedPath);
+      parentBitSetProducer = new QueryBitSetProducer(parentQuery);
+      if (filterQuery != null) {
+        // Filter query is applied to the parent document only
+        filterQuery =
+            QueryNodeMapper.getInstance()
+                .applyQueryNestedPath(filterQuery, indexState, parentNestedPath);
+        filterQuery = new ToChildBlockJoinQuery(filterQuery, parentBitSetProducer);
+      }
+    }
+    return vectorQueryable.getKnnQuery(knnQuery, filterQuery, parentBitSetProducer);
   }
 
   /**