Add filter-based deletion to Milvus vector store (#2127)

Add string-based filter deletion alongside the Filter.Expression-based deletion
for Milvus vector store, providing consistent deletion capabilities with
other vector store implementations.

Key changes:
- Add delete(Filter.Expression) implementation for Milvus store
- Leverage existing MilvusFilterExpressionConverter for filter translation
- Use Milvus client's native delete API with filter expressions
- Add comprehensive integration tests for filter deletion
- Support both simple and complex filter expressions

This maintains consistency with other vector store implementations while
utilizing Milvus-specific APIs for efficient metadata-based deletion.

Author: sobychacko

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023-2024 the original author or authors.
+ * Copyright 2023-2025 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.
@@ -61,6 +61,7 @@
 import org.springframework.ai.vectorstore.AbstractVectorStoreBuilder;
 import org.springframework.ai.vectorstore.SearchRequest;
 import org.springframework.ai.vectorstore.VectorStore;
+import org.springframework.ai.vectorstore.filter.Filter;
 import org.springframework.ai.vectorstore.filter.FilterExpressionConverter;
 import org.springframework.ai.vectorstore.observation.AbstractObservationVectorStore;
 import org.springframework.ai.vectorstore.observation.VectorStoreObservationContext;
@@ -291,6 +292,32 @@ public Optional<Boolean> doDelete(List<String> idList) {
 		return Optional.of(status.getStatus() == Status.Success.getCode());
 	}
 
+	@Override
+	protected void doDelete(Filter.Expression filterExpression) {
+		Assert.notNull(filterExpression, "Filter expression must not be null");
+
+		try {
+			String nativeFilterExpression = this.filterExpressionConverter.convertExpression(filterExpression);
+
+			R<MutationResult> status = this.milvusClient.delete(DeleteParam.newBuilder()
+				.withDatabaseName(this.databaseName)
+				.withCollectionName(this.collectionName)
+				.withExpr(nativeFilterExpression)
+				.build());
+
+			if (status.getStatus() != Status.Success.getCode()) {
+				throw new IllegalStateException("Failed to delete documents by filter: " + status.getMessage());
+			}
+
+			long deleteCount = status.getData().getDeleteCnt();
+			logger.debug("Deleted {} documents matching filter expression", deleteCount);
+		}
+		catch (Exception e) {
+			logger.error("Failed to delete documents by filter: {}", e.getMessage(), e);
+			throw new IllegalStateException("Failed to delete documents by filter", e);
+		}
+	}
+
 	@Override
 	public List<Document> doSimilaritySearch(SearchRequest request) {
 

vector-stores/spring-ai-milvus-store/src/test/java/org/springframework/ai/vectorstore/milvus/MilvusVectorStoreIT.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023-2024 the original author or authors.
+ * Copyright 2023-2025 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.
@@ -22,11 +22,13 @@
 import java.util.List;
 import java.util.Map;
 import java.util.UUID;
+import java.util.stream.Collectors;
 
 import io.milvus.client.MilvusServiceClient;
 import io.milvus.param.ConnectParam;
 import io.milvus.param.IndexType;
 import io.milvus.param.MetricType;
+import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.condition.EnabledIfEnvironmentVariable;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
@@ -42,6 +44,7 @@
 import org.springframework.ai.openai.api.OpenAiApi;
 import org.springframework.ai.vectorstore.SearchRequest;
 import org.springframework.ai.vectorstore.VectorStore;
+import org.springframework.ai.vectorstore.filter.Filter;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.SpringBootConfiguration;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
@@ -56,6 +59,7 @@
  * @author Christian Tzolov
  * @author Eddú Meléndez
  * @author Thomas Vitale
+ * @author Soby Chacko
  */
 @Testcontainers
 @EnabledIfEnvironmentVariable(named = "OPENAI_API_KEY", matches = ".+")
@@ -273,6 +277,107 @@ public void searchWithThreshold(String metricType) {
 			});
 	}
 
+	@Test
+	public void deleteByFilter() {
+		this.contextRunner.withPropertyValues("test.spring.ai.vectorstore.milvus.metricType=COSINE").run(context -> {
+			VectorStore vectorStore = context.getBean(VectorStore.class);
+
+			resetCollection(vectorStore);
+
+			var bgDocument = new Document("The World is Big and Salvation Lurks Around the Corner",
+					Map.of("country", "BG", "year", 2020));
+			var nlDocument = new Document("The World is Big and Salvation Lurks Around the Corner",
+					Map.of("country", "NL", "year", 2021));
+			var bgDocument2 = new Document("The World is Big and Salvation Lurks Around the Corner",
+					Map.of("country", "BG", "year", 2023));
+
+			vectorStore.add(List.of(bgDocument, nlDocument, bgDocument2));
+
+			SearchRequest searchRequest = SearchRequest.builder()
+				.query("The World")
+				.topK(5)
+				.similarityThresholdAll()
+				.build();
+
+			List<Document> results = vectorStore.similaritySearch(searchRequest);
+			assertThat(results).hasSize(3);
+
+			Filter.Expression filterExpression = new Filter.Expression(Filter.ExpressionType.EQ,
+					new Filter.Key("country"), new Filter.Value("BG"));
+
+			vectorStore.delete(filterExpression);
+
+			// Verify deletion - should only have NL document remaining
+			results = vectorStore.similaritySearch(searchRequest);
+			assertThat(results).hasSize(1);
+			assertThat(results.get(0).getMetadata()).containsEntry("country", "NL");
+		});
+	}
+
+	@Test
+	public void deleteWithStringFilterExpression() {
+		this.contextRunner.withPropertyValues("test.spring.ai.vectorstore.milvus.metricType=COSINE").run(context -> {
+			VectorStore vectorStore = context.getBean(VectorStore.class);
+
+			resetCollection(vectorStore);
+
+			var bgDocument = new Document("The World is Big and Salvation Lurks Around the Corner",
+					Map.of("country", "BG", "year", 2020));
+			var nlDocument = new Document("The World is Big and Salvation Lurks Around the Corner",
+					Map.of("country", "NL", "year", 2021));
+			var bgDocument2 = new Document("The World is Big and Salvation Lurks Around the Corner",
+					Map.of("country", "BG", "year", 2023));
+
+			vectorStore.add(List.of(bgDocument, nlDocument, bgDocument2));
+
+			var searchRequest = SearchRequest.builder().query("The World").topK(5).similarityThresholdAll().build();
+
+			List<Document> results = vectorStore.similaritySearch(searchRequest);
+			assertThat(results).hasSize(3);
+
+			// Delete using string filter expression
+			vectorStore.delete("country == 'BG'");
+
+			results = vectorStore.similaritySearch(searchRequest);
+			assertThat(results).hasSize(1);
+			assertThat(results.get(0).getMetadata()).containsEntry("country", "NL");
+		});
+	}
+
+	@Test
+	public void deleteWithComplexFilterExpression() {
+		this.contextRunner.withPropertyValues("test.spring.ai.vectorstore.milvus.metricType=COSINE").run(context -> {
+			VectorStore vectorStore = context.getBean(VectorStore.class);
+
+			resetCollection(vectorStore);
+
+			var doc1 = new Document("Content 1", Map.of("type", "A", "priority", 1));
+			var doc2 = new Document("Content 2", Map.of("type", "A", "priority", 2));
+			var doc3 = new Document("Content 3", Map.of("type", "B", "priority", 1));
+
+			vectorStore.add(List.of(doc1, doc2, doc3));
+
+			// Complex filter expression: (type == 'A' AND priority > 1)
+			Filter.Expression priorityFilter = new Filter.Expression(Filter.ExpressionType.GT,
+					new Filter.Key("priority"), new Filter.Value(1));
+			Filter.Expression typeFilter = new Filter.Expression(Filter.ExpressionType.EQ, new Filter.Key("type"),
+					new Filter.Value("A"));
+			Filter.Expression complexFilter = new Filter.Expression(Filter.ExpressionType.AND, typeFilter,
+					priorityFilter);
+
+			vectorStore.delete(complexFilter);
+
+			var results = vectorStore
+				.similaritySearch(SearchRequest.builder().query("Content").topK(5).similarityThresholdAll().build());
+
+			assertThat(results).hasSize(2);
+			assertThat(results.stream().map(doc -> doc.getMetadata().get("type")).collect(Collectors.toList()))
+				.containsExactlyInAnyOrder("A", "B");
+			assertThat(results.stream().map(doc -> doc.getMetadata().get("priority")).collect(Collectors.toList()))
+				.containsExactlyInAnyOrder(1, 1);
+		});
+	}
+
 	@SpringBootConfiguration
 	@EnableAutoConfiguration(exclude = { DataSourceAutoConfiguration.class })
 	public static class TestApplication {