[inference_metadata_fields] Clear inference results on explicit nulls

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/action/filter/ShardBulkInferenceActionFilter.java

@@ -39,6 +39,7 @@
 import org.elasticsearch.inference.UnparsedModel;
 import org.elasticsearch.rest.RestStatus;
 import org.elasticsearch.tasks.Task;
+import org.elasticsearch.xcontent.XContent;
 import org.elasticsearch.xpack.core.inference.results.ChunkedInferenceError;
 import org.elasticsearch.xpack.inference.mapper.SemanticTextField;
 import org.elasticsearch.xpack.inference.mapper.SemanticTextFieldMapper;
@@ -50,6 +51,7 @@
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashMap;
+import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -67,6 +69,8 @@
  */
 public class ShardBulkInferenceActionFilter implements MappedActionFilter {
     protected static final int DEFAULT_BATCH_SIZE = 512;
+    private static final Object EXPLICIT_NULL = new Object();
+    private static final ChunkedInference EMPTY_CHUNKED_INFERENCE = new EmptyChunkedInference();
 
     private final ClusterService clusterService;
     private final InferenceServiceRegistry inferenceServiceRegistry;
@@ -393,11 +397,22 @@ private void applyInferenceResponses(BulkItemRequest item, FieldInferenceRespons
             for (var entry : response.responses.entrySet()) {
                 var fieldName = entry.getKey();
                 var responses = entry.getValue();
-                var model = responses.get(0).model();
+                Model model = null;
+
+                InferenceFieldMetadata inferenceFieldMetadata = fieldInferenceMap.get(fieldName);
+                if (inferenceFieldMetadata == null) {
+                    throw new IllegalStateException("No inference field metadata for field [" + fieldName + "]");
+                }
+
                 // ensure that the order in the original field is consistent in case of multiple inputs
                 Collections.sort(responses, Comparator.comparingInt(FieldInferenceResponse::inputOrder));
                 Map<String, List<SemanticTextField.Chunk>> chunkMap = new LinkedHashMap<>();
                 for (var resp : responses) {
+                    // Get the first non-null model from the response list
+                    if (model == null) {
+                        model = resp.model;
+                    }
+
                     var lst = chunkMap.computeIfAbsent(resp.sourceField, k -> new ArrayList<>());
                     lst.addAll(
                         SemanticTextField.toSemanticTextFieldChunks(
@@ -409,21 +424,26 @@ private void applyInferenceResponses(BulkItemRequest item, FieldInferenceRespons
                         )
                     );
                 }
+
                 List<String> inputs = responses.stream()
                     .filter(r -> r.sourceField().equals(fieldName))
                     .map(r -> r.input)
                     .collect(Collectors.toList());
+
+                // The model can be null if we are only processing update requests that clear inference results. This is ok because we will
+                // merge in the field's existing model settings on the data node.
                 var result = new SemanticTextField(
                     useLegacyFormat,
                     fieldName,
                     useLegacyFormat ? inputs : null,
                     new SemanticTextField.InferenceResult(
-                        model.getInferenceEntityId(),
-                        new SemanticTextField.ModelSettings(model),
+                        inferenceFieldMetadata.getInferenceId(),
+                        model != null ? new SemanticTextField.ModelSettings(model) : null,
                         chunkMap
                     ),
                     indexRequest.getContentType()
                 );
+
                 if (useLegacyFormat) {
                     SemanticTextUtils.insertValue(fieldName, newDocMap, result);
                 } else {
@@ -490,7 +510,8 @@ private Map<String, List<FieldInferenceRequest>> createFieldInferenceRequests(Bu
                     } else {
                         var inferenceMetadataFieldsValue = XContentMapValues.extractValue(
                             InferenceMetadataFieldsMapper.NAME + "." + field,
-                            docMap
+                            docMap,
+                            EXPLICIT_NULL
                         );
                         if (inferenceMetadataFieldsValue != null) {
                             // Inference has already been computed
@@ -500,9 +521,22 @@ private Map<String, List<FieldInferenceRequest>> createFieldInferenceRequests(Bu
 
                     int order = 0;
                     for (var sourceField : entry.getSourceFields()) {
-                        // TODO: Detect when the field is provided with an explicit null value
-                        var valueObj = XContentMapValues.extractValue(sourceField, docMap);
-                        if (valueObj == null) {
+                        var valueObj = XContentMapValues.extractValue(sourceField, docMap, EXPLICIT_NULL);
+                        if (useLegacyFormat == false && isUpdateRequest && valueObj == EXPLICIT_NULL) {
+                            /**
+                             * It's an update request, and the source field is explicitly set to null,
+                             * so we need to propagate this information to the inference fields metadata
+                             * to overwrite any inference previously computed on the field.
+                             * This ensures that the field is treated as intentionally cleared,
+                             * preventing any unintended carryover of prior inference results.
+                             */
+                            var slot = ensureResponseAccumulatorSlot(itemIndex);
+                            slot.addOrUpdateResponse(
+                                new FieldInferenceResponse(field, sourceField, null, order++, 0, null, EMPTY_CHUNKED_INFERENCE)
+                            );
+                            continue;
+                        }
+                        if (valueObj == null || valueObj == EXPLICIT_NULL) {
                             if (isUpdateRequest && useLegacyFormat) {
                                 addInferenceResponseFailure(
                                     item.id(),
@@ -552,4 +586,11 @@ static IndexRequest getIndexRequestOrNull(DocWriteRequest<?> docWriteRequest) {
             return null;
         }
     }
+
+    private static class EmptyChunkedInference implements ChunkedInference {
+        @Override
+        public Iterator<Chunk> chunksAsMatchedTextAndByteReference(XContent xcontent) {
+            return Collections.emptyIterator();
+        }
+    }
 }

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/mapper/SemanticTextField.java

@@ -345,9 +345,10 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
         );
 
         INFERENCE_RESULT_PARSER.declareString(constructorArg(), new ParseField(INFERENCE_ID_FIELD));
-        INFERENCE_RESULT_PARSER.declareObject(
+        INFERENCE_RESULT_PARSER.declareObjectOrNull(
             constructorArg(),
             (p, c) -> MODEL_SETTINGS_PARSER.parse(p, null),
+            null,
             new ParseField(MODEL_SETTINGS_FIELD)
         );
         INFERENCE_RESULT_PARSER.declareField(constructorArg(), (p, c) -> {

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/mapper/SemanticTextFieldMapper.java

@@ -895,7 +895,7 @@ private static boolean canMergeModelSettings(
         if (Objects.equals(previous, current)) {
             return true;
         }
-        if (previous == null) {
+        if (previous == null ^ current == null) {
             return true;
         }
         conflicts.addConflict("model_settings", "");

x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/action/filter/ShardBulkInferenceActionFilterTests.java

@@ -18,6 +18,7 @@
 import org.elasticsearch.action.index.IndexRequest;
 import org.elasticsearch.action.support.ActionFilterChain;
 import org.elasticsearch.action.support.WriteRequest;
+import org.elasticsearch.action.update.UpdateRequest;
 import org.elasticsearch.cluster.ClusterName;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.metadata.IndexMetadata;
@@ -205,6 +206,11 @@ public void testItemFailures() throws Exception {
                     XContentMapValues.extractValue(useLegacyFormat ? "field1.text" : "field1", actualRequest.sourceAsMap()),
                     equalTo("I am a success")
                 );
+                if (useInferenceMetadataFieldsFormat) {
+                    assertNotNull(
+                        XContentMapValues.extractValue(InferenceMetadataFieldsMapper.NAME + ".field1", actualRequest.sourceAsMap())
+                    );
+                }
 
                 // item 2 is a failure
                 assertNotNull(bulkShardRequest.items()[2].getPrimaryResponse());
@@ -232,6 +238,98 @@ public void testItemFailures() throws Exception {
         awaitLatch(chainExecuted, 10, TimeUnit.SECONDS);
     }
 
+    @SuppressWarnings({ "unchecked", "rawtypes" })
+    public void testExplicitNull() throws Exception {
+        StaticModel model = StaticModel.createRandomInstance();
+
+        ShardBulkInferenceActionFilter filter = createFilter(
+            threadPool,
+            Map.of(model.getInferenceEntityId(), model),
+            randomIntBetween(1, 10),
+            IndexVersion.current()
+        );
+        model.putResult("I am a failure", new ChunkedInferenceError(new IllegalArgumentException("boom")));
+        model.putResult("I am a success", randomChunkedInferenceEmbeddingSparse(List.of("I am a success")));
+        CountDownLatch chainExecuted = new CountDownLatch(1);
+        ActionFilterChain actionFilterChain = (task, action, request, listener) -> {
+            try {
+                BulkShardRequest bulkShardRequest = (BulkShardRequest) request;
+                assertNull(bulkShardRequest.getInferenceFieldMap());
+                assertThat(bulkShardRequest.items().length, equalTo(5));
+
+                Object explicitNull = new Object();
+                // item 0
+                assertNull(bulkShardRequest.items()[0].getPrimaryResponse());
+                IndexRequest actualRequest = getIndexRequestOrNull(bulkShardRequest.items()[0].request());
+                assertTrue(XContentMapValues.extractValue("obj.field1", actualRequest.sourceAsMap(), explicitNull) == explicitNull);
+                assertNull(XContentMapValues.extractValue(InferenceMetadataFieldsMapper.NAME, actualRequest.sourceAsMap(), explicitNull));
+
+                // item 1 is a success
+                assertNull(bulkShardRequest.items()[1].getPrimaryResponse());
+                actualRequest = getIndexRequestOrNull(bulkShardRequest.items()[1].request());
+                assertThat(XContentMapValues.extractValue("obj.field1", actualRequest.sourceAsMap()), equalTo("I am a success"));
+                assertNotNull(
+                    XContentMapValues.extractValue(
+                        InferenceMetadataFieldsMapper.NAME + ".obj.field1",
+                        actualRequest.sourceAsMap(),
+                        explicitNull
+                    )
+                );
+
+                // item 2 is a failure
+                assertNotNull(bulkShardRequest.items()[2].getPrimaryResponse());
+                assertTrue(bulkShardRequest.items()[2].getPrimaryResponse().isFailed());
+                var failure = bulkShardRequest.items()[2].getPrimaryResponse().getFailure();
+                assertThat(failure.getCause().getCause().getMessage(), containsString("boom"));
+
+                // item 3
+                assertNull(bulkShardRequest.items()[3].getPrimaryResponse());
+                actualRequest = getIndexRequestOrNull(bulkShardRequest.items()[3].request());
+                assertTrue(XContentMapValues.extractValue("obj.field1", actualRequest.sourceAsMap(), explicitNull) == explicitNull);
+                assertTrue(
+                    XContentMapValues.extractValue(
+                        InferenceMetadataFieldsMapper.NAME + ".obj.field1",
+                        actualRequest.sourceAsMap(),
+                        explicitNull
+                    ) == explicitNull
+                );
+
+                // item 4
+                assertNull(bulkShardRequest.items()[4].getPrimaryResponse());
+                actualRequest = getIndexRequestOrNull(bulkShardRequest.items()[4].request());
+                assertNull(XContentMapValues.extractValue("obj.field1", actualRequest.sourceAsMap(), explicitNull));
+                assertNull(
+                    XContentMapValues.extractValue(
+                        InferenceMetadataFieldsMapper.NAME + ".obj.field1",
+                        actualRequest.sourceAsMap(),
+                        explicitNull
+                    )
+                );
+            } finally {
+                chainExecuted.countDown();
+            }
+        };
+        ActionListener actionListener = mock(ActionListener.class);
+        Task task = mock(Task.class);
+
+        Map<String, InferenceFieldMetadata> inferenceFieldMap = Map.of(
+            "obj.field1",
+            new InferenceFieldMetadata("obj.field1", model.getInferenceEntityId(), new String[] { "obj.field1" })
+        );
+        BulkItemRequest[] items = new BulkItemRequest[5];
+        Map<String, Object> sourceWithNull = new HashMap<>();
+        sourceWithNull.put("field1", null);
+        items[0] = new BulkItemRequest(0, new IndexRequest("index").source(Map.of("obj", sourceWithNull)));
+        items[1] = new BulkItemRequest(1, new IndexRequest("index").source("obj.field1", "I am a success"));
+        items[2] = new BulkItemRequest(2, new IndexRequest("index").source("obj.field1", "I am a failure"));
+        items[3] = new BulkItemRequest(3, new UpdateRequest().doc(new IndexRequest("index").source(Map.of("obj", sourceWithNull))));
+        items[4] = new BulkItemRequest(3, new UpdateRequest().doc(new IndexRequest("index").source(Map.of("field2", "value"))));
+        BulkShardRequest request = new BulkShardRequest(new ShardId("test", "test", 0), WriteRequest.RefreshPolicy.NONE, items);
+        request.setInferenceFieldMap(inferenceFieldMap);
+        filter.apply(task, TransportShardBulkAction.ACTION_NAME, request, actionListener, actionFilterChain);
+        awaitLatch(chainExecuted, 10, TimeUnit.SECONDS);
+    }
+
     @SuppressWarnings({ "unchecked", "rawtypes" })
     public void testManyRandomDocs() throws Exception {
         Map<String, StaticModel> inferenceModelMap = new HashMap<>();