Updates the SearchRequest class to be non-final and adds a MilvusSearchRequest subclass that includes Milvus-specific fields for native expressions and search parameters.

spring-ai-core/src/main/java/org/springframework/ai/vectorstore/SearchRequest.java

@@ -33,7 +33,7 @@
  * @author Thomas Vitale
  * @author Ilayaperumal Gopinathan
  */
-public final class SearchRequest {
+public class SearchRequest {
 
 	/**
 	 * Similarity threshold that accepts all search scores. A threshold value of 0.0 means
@@ -71,6 +71,16 @@ public static Builder from(SearchRequest originalSearchRequest) {
 			.filterExpression(originalSearchRequest.getFilterExpression());
 	}
 
+	public SearchRequest() {
+	}
+
+	protected SearchRequest(SearchRequest original) {
+		this.query = original.query;
+		this.topK = original.topK;
+		this.similarityThreshold = original.similarityThreshold;
+		this.filterExpression = original.filterExpression;
+	}
+
 	public String getQuery() {
 		return this.query;
 	}

vector-stores/spring-ai-milvus-store/src/main/java/org/springframework/ai/vectorstore/milvus/MilvusSearchRequest.java

@@ -0,0 +1,162 @@
+package org.springframework.ai.vectorstore.milvus;
+
+import org.springframework.ai.vectorstore.SearchRequest;
+import org.springframework.ai.vectorstore.filter.Filter;
+import org.springframework.lang.Nullable;
+
+/**
+ * A specialized {@link SearchRequest} for Milvus vector search, extending the base request
+ * with Milvus-specific parameters.
+ * <p>
+ * This class introduces two additional fields:
+ * <ul>
+ *   <li>{@code nativeExpression} - A native Milvus filter expression (e.g., "city LIKE 'New%'").</li>
+ *   <li>{@code searchParamsJson} - A JSON string containing search parameters (e.g., "{\"nprobe\":128}").</li>
+ * </ul>
+ * <p>
+ * Use the {@link MilvusBuilder} to construct instances of this class.
+ *
+ * @author waileong
+ */
+public final class MilvusSearchRequest extends SearchRequest {
+
+	@Nullable
+	private final String nativeExpression;
+
+	@Nullable
+	private final String searchParamsJson;
+
+	/**
+	 * Private constructor to initialize a MilvusSearchRequest using the base request and builder.
+	 *
+	 * @param baseRequest The base {@link SearchRequest} containing standard search fields.
+	 * @param builder     The {@link MilvusBuilder} containing Milvus-specific parameters.
+	 */
+	private MilvusSearchRequest(SearchRequest baseRequest, MilvusBuilder builder) {
+		super(baseRequest); // Copy all standard fields
+		this.nativeExpression = builder.nativeExpression;
+		this.searchParamsJson = builder.searchParamsJson;
+	}
+
+	/**
+	 * Retrieves the native Milvus filter expression.
+	 *
+	 * @return A string representing the native Milvus expression, or {@code null} if not set.
+	 */
+	@Nullable
+	public String getNativeExpression() {
+		return this.nativeExpression;
+	}
+
+	/**
+	 * Retrieves the JSON-encoded search parameters.
+	 *
+	 * @return A JSON string containing search parameters, or {@code null} if not set.
+	 */
+	@Nullable
+	public String getSearchParamsJson() {
+		return this.searchParamsJson;
+	}
+
+	/**
+	 * Creates a new {@link MilvusBuilder} for constructing a {@link MilvusSearchRequest}.
+	 *
+	 * @return A new {@link MilvusBuilder} instance.
+	 */
+	public static MilvusBuilder milvusBuilder() {
+		return new MilvusBuilder();
+	}
+
+	/**
+	 * Builder class for constructing instances of {@link MilvusSearchRequest}.
+	 */
+	public static class MilvusBuilder {
+
+		private final SearchRequest.Builder baseBuilder = SearchRequest.builder();
+
+		@Nullable
+		private String nativeExpression;
+		@Nullable
+		private String searchParamsJson;
+
+		/**
+		 * {@link Builder#query(java.lang.String)}
+		 */
+		public MilvusBuilder query(String query) {
+			this.baseBuilder.query(query);
+			return this;
+		}
+
+		/**
+		 * {@link Builder#topK(int)}
+		 */
+		public MilvusBuilder topK(int topK) {
+			this.baseBuilder.topK(topK);
+			return this;
+		}
+
+		/**
+		 * {@link Builder#similarityThreshold(double)}
+		 */
+		public MilvusBuilder similarityThreshold(double threshold) {
+			this.baseBuilder.similarityThreshold(threshold);
+			return this;
+		}
+
+		/**
+		 * {@link Builder#similarityThresholdAll()}
+		 */
+		public MilvusBuilder similarityThresholdAll() {
+			this.baseBuilder.similarityThresholdAll();
+			return this;
+		}
+
+		/**
+		 * {@link Builder#filterExpression(String)}
+		 */
+		public MilvusBuilder filterExpression(String textExpression) {
+			this.baseBuilder.filterExpression(textExpression);
+			return this;
+		}
+
+		/**
+		 * {@link Builder#filterExpression(Filter.Expression)}
+		 */
+		public MilvusBuilder filterExpression(Filter.Expression expression) {
+			this.baseBuilder.filterExpression(expression);
+			return this;
+		}
+
+		/**
+		 * Sets the native Milvus filter expression.
+		 *
+		 * @param nativeExpression The native Milvus expression string.
+		 * @return This builder instance.
+		 */
+		public MilvusBuilder nativeExpression(String nativeExpression) {
+			this.nativeExpression = nativeExpression;
+			return this;
+		}
+
+		/**
+		 * Sets the JSON-encoded search parameters.
+		 *
+		 * @param searchParamsJson A JSON string containing search parameters.
+		 * @return This builder instance.
+		 */
+		public MilvusBuilder searchParamsJson(String searchParamsJson) {
+			this.searchParamsJson = searchParamsJson;
+			return this;
+		}
+
+		/**
+		 * Builds and returns a {@link MilvusSearchRequest} instance.
+		 *
+		 * @return A new {@link MilvusSearchRequest} object with the specified parameters.
+		 */
+		public MilvusSearchRequest build() {
+			SearchRequest parentRequest = this.baseBuilder.build();
+			return new MilvusSearchRequest(parentRequest, this);
+		}
+	}
+}

vector-stores/spring-ai-milvus-store/src/main/java/org/springframework/ai/vectorstore/milvus/MilvusVectorStore.java

@@ -318,9 +318,19 @@ protected void doDelete(Filter.Expression filterExpression) {
 
 	@Override
 	public List<Document> doSimilaritySearch(SearchRequest request) {
-
-		String nativeFilterExpressions = (request.getFilterExpression() != null)
-				? this.filterExpressionConverter.convertExpression(request.getFilterExpression()) : "";
+		String nativeFilterExpressions = "";
+		String searchParamsJson = null;
+		if (request instanceof MilvusSearchRequest milvusReq){
+			if(milvusReq.getNativeExpression() != null && !milvusReq.getNativeExpression().isEmpty()) {
+				nativeFilterExpressions = milvusReq.getNativeExpression();
+			}
+			if (milvusReq.getSearchParamsJson() != null && !milvusReq.getSearchParamsJson().isEmpty()) {
+				searchParamsJson = milvusReq.getSearchParamsJson();
+			}
+		} else {
+			nativeFilterExpressions = (request.getFilterExpression() != null)
+					? this.filterExpressionConverter.convertExpression(request.getFilterExpression()) : "";
+		}
 
 		Assert.notNull(request.getQuery(), "Query string must not be null");
 		List<String> outFieldNames = new ArrayList<>();
@@ -343,6 +353,10 @@ public List<Document> doSimilaritySearch(SearchRequest request) {
 			searchParamBuilder.withExpr(nativeFilterExpressions);
 		}
 
+		if (StringUtils.hasText(searchParamsJson)) {
+			searchParamBuilder.withParams(searchParamsJson);
+		}
+
 		R<SearchResults> respSearch = this.milvusClient.search(searchParamBuilder.build());
 
 		if (respSearch.getException() != null) {