[7.x][ML] Outlier detection mapping for nested feature influence (#62068) (#62150)

Adds mappings for outlier detection results.

Backport of #62068

Author: dimitris-athanasiou

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/dataframe/analyses/OutlierDetection.java

@@ -13,6 +13,9 @@
 import org.elasticsearch.common.xcontent.ObjectParser;
 import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentParser;
+import org.elasticsearch.index.mapper.KeywordFieldMapper;
+import org.elasticsearch.index.mapper.NumberFieldMapper;
+import org.elasticsearch.index.mapper.ObjectMapper;
 import org.elasticsearch.xpack.core.ml.inference.trainedmodel.InferenceConfig;
 import org.elasticsearch.xpack.core.ml.utils.ExceptionsHelper;
 
@@ -56,6 +59,20 @@ public static OutlierDetection fromXContent(XContentParser parser, boolean ignor
 
     private static final List<String> PROGRESS_PHASES = Collections.singletonList("computing_outliers");
 
+    static final Map<String, Object> FEATURE_INFLUENCE_MAPPING;
+    static {
+        Map<String, Object> properties = new HashMap<>();
+        properties.put("feature_name", Collections.singletonMap("type", KeywordFieldMapper.CONTENT_TYPE));
+        properties.put("influence", Collections.singletonMap("type", NumberFieldMapper.NumberType.DOUBLE.typeName()));
+
+        Map<String, Object> mapping = new HashMap<>();
+        mapping.put("dynamic", false);
+        mapping.put("type", ObjectMapper.NESTED_CONTENT_TYPE);
+        mapping.put("properties", properties);
+
+        FEATURE_INFLUENCE_MAPPING = Collections.unmodifiableMap(mapping);
+    }
+
     /**
      * The number of neighbors. Leave unspecified for dynamic detection.
      */
@@ -229,7 +246,11 @@ public List<FieldCardinalityConstraint> getFieldCardinalityConstraints() {
 
     @Override
     public Map<String, Object> getExplicitlyMappedFields(Map<String, Object> mappingsProperties, String resultsFieldName) {
-        return Collections.emptyMap();
+        Map<String, Object> additionalProperties = new HashMap<>();
+        additionalProperties.put(resultsFieldName + ".outlier_score",
+            Collections.singletonMap("type", NumberFieldMapper.NumberType.DOUBLE.typeName()));
+        additionalProperties.put(resultsFieldName + ".feature_influence", FEATURE_INFLUENCE_MAPPING);
+        return additionalProperties;
     }
 
     @Override

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/dataframe/analyses/OutlierDetectionTests.java

@@ -8,15 +8,17 @@
 import org.elasticsearch.Version;
 import org.elasticsearch.common.io.stream.Writeable;
 import org.elasticsearch.common.xcontent.XContentParser;
+import org.elasticsearch.index.mapper.NumberFieldMapper;
 import org.elasticsearch.xpack.core.ml.AbstractBWCSerializationTestCase;
 
 import java.io.IOException;
+import java.util.Collections;
 import java.util.Map;
 
-import static org.hamcrest.Matchers.anEmptyMap;
 import static org.hamcrest.Matchers.closeTo;
 import static org.hamcrest.Matchers.empty;
 import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.hasKey;
 import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.nullValue;
 
@@ -106,7 +108,13 @@ public void testFieldCardinalityLimitsIsEmpty() {
     }
 
     public void testGetExplicitlyMappedFields() {
-        assertThat(createTestInstance().getExplicitlyMappedFields(null, null), is(anEmptyMap()));
+        Map<String, Object> mappedFields = createTestInstance().getExplicitlyMappedFields(null, "test");
+        assertThat(mappedFields.size(), equalTo(2));
+        assertThat(mappedFields, hasKey("test.outlier_score"));
+        assertThat(mappedFields.get("test.outlier_score"),
+            equalTo(Collections.singletonMap("type", NumberFieldMapper.NumberType.DOUBLE.typeName())));
+        assertThat(mappedFields, hasKey("test.feature_influence"));
+        assertThat(mappedFields.get("test.feature_influence"), equalTo(OutlierDetection.FEATURE_INFLUENCE_MAPPING));
     }
 
     public void testGetStateDocId() {