Fixed field value from nested mapping when train model

Signed-off-by: Junqiu Lei <[email protected]>

CHANGELOG.md

@@ -18,6 +18,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 ### Enhancements
 ### Bug Fixes
 * Fix use-after-free case on nmslib search path [#1305](https://github.com/opensearch-project/k-NN/pull/1305)
+* Fixed field value from nested mapping when train model [#1318](https://github.com/opensearch-project/k-NN/pull/1318)
 ### Infrastructure
 * Upgrade gradle to 8.4 [1289](https://github.com/opensearch-project/k-NN/pull/1289)
 ### Documentation

src/main/java/org/opensearch/knn/index/IndexUtil.java

@@ -59,6 +59,31 @@ public static int getFileSizeInKB(String filePath) {
         return Math.toIntExact((file.length() / BYTES_PER_KILOBYTES) + 1L); // Add one so that integer division rounds up
     }
 
+    /**
+     * Retrieves a field mapping from properties map by recursively searching through the map.
+     *
+     * @param properties A map representing properties, where each key is a property name and
+     *                   the value is either a sub-map of properties or the property value itself.
+     * @param field      The name of the field to retrieve.
+     * @return           The value of the field if found, or null if the field is not present in the map.
+     */
+    public static Object getFieldMapping(Map<String, Object> properties, String field) {
+        if (properties.containsKey(field)) {
+            return properties.get(field);
+        } else {
+            for (Map.Entry<String, Object> entry : properties.entrySet()) {
+                Object value = entry.getValue();
+                if (value instanceof Map) {
+                    Object result = getFieldMapping((Map<String, Object>) value, field);
+                    if (result != null) {
+                        return result;
+                    }
+                }
+            }
+        }
+        return null;
+    }
+
     /**
      * Validate that a field is a k-NN vector field and has the expected dimension
      *
@@ -100,7 +125,7 @@ public static ValidationException validateKnnField(
             return exception;
         }
 
-        Object fieldMapping = properties.get(field);
+        Object fieldMapping = getFieldMapping(properties, field);
 
         // Check field existence
         if (fieldMapping == null) {

src/test/java/org/opensearch/knn/index/IndexUtilTests.java

@@ -20,6 +20,8 @@
 import org.opensearch.knn.KNNTestCase;
 import org.opensearch.knn.index.util.KNNEngine;
 
+import java.util.Collections;
+import java.util.HashMap;
 import java.util.Map;
 
 import static org.mockito.ArgumentMatchers.anyString;
@@ -67,4 +69,26 @@ public void testGetLoadParameters() {
         assertEquals(spaceType2.getValue(), loadParameters.get(SPACE_TYPE));
         assertEquals(efSearchValue, loadParameters.get(HNSW_ALGO_EF_SEARCH));
     }
+
+    public void testGetFieldMappingNonNestedField() {
+        Map<String, Object> properties = new HashMap<>();
+        properties.put("top_level_field", "top_level_value");
+
+        Object result = IndexUtil.getFieldMapping(properties, "top_level_field");
+        assertEquals("top_level_value", result);
+    }
+
+    public void testGetFieldMappingNestedField() {
+        Map<String, Object> deepNestedProperties = new HashMap<>();
+        deepNestedProperties.put("deep_inner_field", "deep_value");
+
+        Map<String, Object> nestedProperties = new HashMap<>();
+        nestedProperties.put("nested", Collections.singletonMap("properties", deepNestedProperties));
+
+        Map<String, Object> properties = new HashMap<>();
+        properties.put("top", Collections.singletonMap("properties", nestedProperties));
+
+        Object deepResult = IndexUtil.getFieldMapping(properties, "deep_inner_field");
+        assertEquals("deep_value", deepResult);
+    }
 }