Add support for $vectorSearch aggregation stage.

Closes #4706
Original pull request: #4882

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/DefaultIndexOperations.java

@@ -20,14 +20,15 @@
 import java.util.List;
 
 import org.bson.Document;
-
 import org.springframework.dao.DataAccessException;
 import org.springframework.data.mongodb.MongoDatabaseFactory;
 import org.springframework.data.mongodb.UncategorizedMongoDbException;
 import org.springframework.data.mongodb.core.convert.QueryMapper;
+import org.springframework.data.mongodb.core.index.DefaultVectorIndexOperations;
 import org.springframework.data.mongodb.core.index.IndexDefinition;
 import org.springframework.data.mongodb.core.index.IndexInfo;
 import org.springframework.data.mongodb.core.index.IndexOperations;
+import org.springframework.data.mongodb.core.index.VectorIndexOperations;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
@@ -51,11 +52,11 @@ public class DefaultIndexOperations implements IndexOperations {
 
 	private static final String PARTIAL_FILTER_EXPRESSION_KEY = "partialFilterExpression";
 
-	private final String collectionName;
-	private final QueryMapper mapper;
-	private final @Nullable Class<?> type;
+	protected final String collectionName;
+	protected final QueryMapper mapper;
+	protected final @Nullable Class<?> type;
 
-	private final MongoOperations mongoOperations;
+	protected final MongoOperations mongoOperations;
 
 	/**
 	 * Creates a new {@link DefaultIndexOperations}.
@@ -133,7 +134,7 @@ public String ensureIndex(IndexDefinition indexDefinition) {
 	}
 
 	@Nullable
-	private MongoPersistentEntity<?> lookupPersistentEntity(@Nullable Class<?> entityType, String collection) {
+	protected MongoPersistentEntity<?> lookupPersistentEntity(@Nullable Class<?> entityType, String collection) {
 
 		if (entityType != null) {
 			return mapper.getMappingContext().getRequiredPersistentEntity(entityType);
@@ -209,6 +210,11 @@ private List<IndexInfo> getIndexData(MongoCursor<Document> cursor) {
 		});
 	}
 
+	@Override
+	public VectorIndexOperations vectorIndex() {
+		return new DefaultVectorIndexOperations(mongoOperations, collectionName, type);
+	}
+
 	@Nullable
 	public <T> T execute(CollectionCallback<T> callback) {
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/VectorSearchOperation.java

@@ -0,0 +1,321 @@
+/*
+ * Copyright 2024 the original author or authors.
+ *
+ * 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
+ *
+ *      https://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 org.springframework.data.mongodb.core.aggregation;
+
+import java.util.Arrays;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.function.Consumer;
+import java.util.stream.Collectors;
+
+import org.bson.Document;
+import org.springframework.data.domain.Limit;
+import org.springframework.data.mongodb.core.query.Criteria;
+import org.springframework.data.mongodb.core.query.CriteriaDefinition;
+import org.springframework.lang.Nullable;
+import org.springframework.util.StringUtils;
+
+/**
+ * @author Christoph Strobl
+ */
+public class VectorSearchOperation implements AggregationOperation {
+
+	public enum SearchType {
+
+		/** MongoDB Server default (value will be omitted) */
+		DEFAULT,
+		/** Approximate Nearest Neighbour */
+		ANN,
+		/** Exact Nearest Neighbour */
+		ENN
+	}
+
+	// A query path cannot only contain the name of the filed but may also hold additional information about the
+	// analyzer to use;
+	// "path": [ "names", "notes", { "value": "comments", "multi": "mySecondaryAnalyzer" } ]
+	// see: https://www.mongodb.com/docs/atlas/atlas-search/path-construction/#std-label-ref-path
+	public static class QueryPaths {
+
+		Set<QueryPath<?>> paths;
+
+		public static QueryPaths of(QueryPath<String> path) {
+
+			QueryPaths queryPaths = new QueryPaths();
+			queryPaths.paths = new LinkedHashSet<>(2);
+			queryPaths.paths.add(path);
+			return queryPaths;
+		}
+
+		Object getPathObject() {
+
+			if (paths.size() == 1) {
+				return paths.iterator().next().value();
+			}
+			return paths.stream().map(QueryPath::value).collect(Collectors.toList());
+		}
+	}
+
+	public interface QueryPath<T> {
+
+		T value();
+
+		static QueryPath<String> path(String field) {
+			return new SimplePath(field);
+		}
+
+		static QueryPath<Map<String, Object>> wildcard(String field) {
+			return new WildcardPath(field);
+		}
+
+		static QueryPath<Map<String, Object>> multi(String field, String analyzer) {
+			return new MultiPath(field, analyzer);
+		}
+	}
+
+	public static class SimplePath implements QueryPath<String> {
+
+		String name;
+
+		public SimplePath(String name) {
+			this.name = name;
+		}
+
+		@Override
+		public String value() {
+			return name;
+		}
+	}
+
+	public static class WildcardPath implements QueryPath<Map<String, Object>> {
+
+		String name;
+
+		public WildcardPath(String name) {
+			this.name = name;
+		}
+
+		@Override
+		public Map<String, Object> value() {
+			return Map.of("wildcard", name);
+		}
+	}
+
+	public static class MultiPath implements QueryPath<Map<String, Object>> {
+
+		String field;
+		String analyzer;
+
+		public MultiPath(String field, String analyzer) {
+			this.field = field;
+			this.analyzer = analyzer;
+		}
+
+		@Override
+		public Map<String, Object> value() {
+			return Map.of("value", field, "multi", analyzer);
+		}
+	}
+
+	private SearchType searchType;
+	private CriteriaDefinition filter;
+	private String indexName;
+	private Limit limit;
+	private Integer numCandidates;
+	private QueryPaths path;
+	private List<Double> vector;
+
+	private String score;
+	private Consumer<Criteria> scoreCriteria;
+
+	private VectorSearchOperation(SearchType searchType, CriteriaDefinition filter, String indexName, Limit limit,
+			Integer numCandidates, QueryPaths path, List<Double> vector, String searchScore,
+			Consumer<Criteria> scoreCriteria) {
+
+		this.searchType = searchType;
+		this.filter = filter;
+		this.indexName = indexName;
+		this.limit = limit;
+		this.numCandidates = numCandidates;
+		this.path = path;
+		this.vector = vector;
+		this.score = searchScore;
+		this.scoreCriteria = scoreCriteria;
+	}
+
+	public VectorSearchOperation(String indexName, QueryPaths path, Limit limit, List<Double> vector) {
+		this(SearchType.DEFAULT, null, indexName, limit, null, path, vector, null, null);
+	}
+
+	static PathContributor search(String index) {
+		return new VectorSearchBuilder().index(index);
+	}
+
+	public VectorSearchOperation(String indexName, String path, Limit limit, List<Double> vector) {
+		this(indexName, QueryPaths.of(QueryPath.path(path)), limit, vector);
+	}
+
+	public VectorSearchOperation searchType(SearchType searchType) {
+		return new VectorSearchOperation(searchType, filter, indexName, limit, numCandidates, path, vector, score,
+				scoreCriteria);
+	}
+
+	public VectorSearchOperation filter(Document filter) {
+
+		return filter(new CriteriaDefinition() {
+			@Override
+			public Document getCriteriaObject() {
+				return filter;
+			}
+
+			@Nullable
+			@Override
+			public String getKey() {
+				return null;
+			}
+		});
+	}
+
+	public VectorSearchOperation filter(CriteriaDefinition filter) {
+		return new VectorSearchOperation(searchType, filter, indexName, limit, numCandidates, path, vector, score,
+				scoreCriteria);
+	}
+
+	public VectorSearchOperation numCandidates(int numCandidates) {
+		return new VectorSearchOperation(searchType, filter, indexName, limit, numCandidates, path, vector, score,
+				scoreCriteria);
+	}
+
+	public VectorSearchOperation searchScore() {
+		return searchScore("score");
+	}
+
+	public VectorSearchOperation searchScore(String scoreFieldName) {
+		return new VectorSearchOperation(searchType, filter, indexName, limit, numCandidates, path, vector, scoreFieldName,
+				scoreCriteria);
+	}
+
+	public VectorSearchOperation filterBySore(Consumer<Criteria> score) {
+		return new VectorSearchOperation(searchType, filter, indexName, limit, numCandidates, path, vector,
+				StringUtils.hasText(this.score) ? this.score : "score", score);
+	}
+
+	@Override
+	public Document toDocument(AggregationOperationContext context) {
+
+		Document $vectorSearch = new Document();
+
+		$vectorSearch.append("index", indexName);
+		$vectorSearch.append("path", path.getPathObject());
+		$vectorSearch.append("queryVector", vector);
+		$vectorSearch.append("limit", limit.max());
+
+		if (searchType != null && !searchType.equals(SearchType.DEFAULT)) {
+			$vectorSearch.append("exact", searchType.equals(SearchType.ENN));
+		}
+
+		if (filter != null) {
+			$vectorSearch.append("filter", context.getMappedObject(filter.getCriteriaObject()));
+		}
+
+		if (numCandidates != null) {
+			$vectorSearch.append("numCandidates", numCandidates);
+		}
+
+		return new Document(getOperator(), $vectorSearch);
+	}
+
+	@Override
+	public List<Document> toPipelineStages(AggregationOperationContext context) {
+
+		if (!StringUtils.hasText(score)) {
+			return List.of(toDocument(context));
+		}
+
+		AddFieldsOperation $vectorSearchScore = Aggregation.addFields().addField(score)
+				.withValueOfExpression("{\"$meta\":\"vectorSearchScore\"}").build();
+
+		if (scoreCriteria == null) {
+			return List.of(toDocument(context), $vectorSearchScore.toDocument(context));
+		}
+
+		Criteria criteria = Criteria.where(score);
+		scoreCriteria.accept(criteria);
+		MatchOperation $filterByScore = Aggregation.match(criteria);
+
+		return List.of(toDocument(context), $vectorSearchScore.toDocument(context), $filterByScore.toDocument(context));
+	}
+
+	@Override
+	public String getOperator() {
+		return "$vectorSearch";
+	}
+
+	public static class VectorSearchBuilder implements PathContributor, VectorContributor, LimitContributor {
+
+		String index;
+		QueryPaths paths;
+		private List<Double> vector;
+
+		PathContributor index(String index) {
+			this.index = index;
+			return this;
+		}
+
+		@Override
+		public VectorContributor path(QueryPaths paths) {
+			this.paths = paths;
+			return this;
+		}
+
+		@Override
+		public VectorSearchOperation limit(Limit limit) {
+			return new VectorSearchOperation(index, paths, limit, vector);
+		}
+
+		@Override
+		public LimitContributor vectors(List<Double> vectors) {
+			this.vector = vectors;
+			return this;
+		}
+	}
+
+	public interface PathContributor {
+		default VectorContributor path(String path) {
+			return path(QueryPaths.of(QueryPath.path(path)));
+		}
+
+		VectorContributor path(QueryPaths paths);
+	}
+
+	public interface VectorContributor {
+		default LimitContributor vectors(Double... vectors) {
+			return vectors(Arrays.asList(vectors));
+		}
+
+		LimitContributor vectors(List<Double> vectors);
+	}
+
+	public interface LimitContributor {
+		default VectorSearchOperation limit(int limit) {
+			return limit(Limit.of(limit));
+		}
+
+		VectorSearchOperation limit(Limit limit);
+	}
+
+}