Improve mutability handling of Source#source()'s map #141534

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Merged

tballison merged 20 commits into elastic:main from tballison:issues/141075

Feb 3, 2026

docs/changelog/141534.yaml

-Original file line number
+Diff line change
@@ -0,0 +1,6 @@
+    area: Search
+    issues:
+     - 141075
+    pr: 141534
+    summary: Fixes bug that prevented retrieving _inference_fields via _source_includes
+    type: bug

server/src/main/java/org/elasticsearch/index/IndexFeatures.java

-Original file line number
+Diff line change
@@ Expand Up / @@ -11,6 +11,7 @@ @@
     import org.elasticsearch.features.FeatureSpecification;
     import org.elasticsearch.features.NodeFeature;
+    import org.elasticsearch.index.mapper.InferenceMetadataFieldsMapper;
     import java.util.Set;
@@ Expand Down Expand Up / @@ -44,7 +45,8 @@ public Set<NodeFeature> getTestFeatures() { @@
                 SYNONYMS_SET_LENIENT_ON_NON_EXISTING,
                 THROW_EXCEPTION_FOR_UNKNOWN_TOKEN_IN_REST_INDEX_PUT_ALIAS_ACTION,
                 THROW_EXCEPTION_ON_INDEX_CREATION_IF_UNSUPPORTED_VALUE_TYPE_IN_ALIAS,
-                SHADOWING_DIMENSIONS_AND_METRICS_IS_VALID_IN_NON_TSDB
+                SHADOWING_DIMENSIONS_AND_METRICS_IS_VALID_IN_NON_TSDB,
+                InferenceMetadataFieldsMapper.INFERENCE_FIELDS_GET_VIA_SOURCE_INCLUDES
             );
         }
     }

server/src/main/java/org/elasticsearch/index/engine/SearchBasedChangesSnapshot.java

-Original file line number
+Diff line change
@@ Expand Up @@
             if (values.isEmpty()) {
                 return originalSource;
             }
-            originalSource.source().put(InferenceMetadataFieldsMapper.NAME, values.get(0));
-            return Source.fromMap(originalSource.source(), originalSource.sourceContentType());
+            return originalSource.withMutations(map -> map.put(InferenceMetadataFieldsMapper.NAME, values.get(0)));
         }
         static IndexSearcher newIndexSearcher(Engine.Searcher engineSearcher) throws IOException {
@@ Expand Down @@

server/src/main/java/org/elasticsearch/index/get/ShardGetService.java

-Original file line number
+Diff line change
@@ Expand Up @@
             inferenceLoader.setNextReader(readerContext);
             List<Object> values = inferenceLoader.fetchValues(source, docId, List.of());
             if (values.size() == 1) {
-                var newSource = source.source();
-                newSource.put(InferenceMetadataFieldsMapper.NAME, values.get(0));
-                return Source.fromMap(newSource, source.sourceContentType());
+                return source.withMutations(map -> map.put(InferenceMetadataFieldsMapper.NAME, values.get(0)));
             }
             return source;
         }
@@ Expand Down @@

server/src/main/java/org/elasticsearch/index/mapper/InferenceMetadataFieldsMapper.java

-Original file line number
+Diff line change
@@ Expand Up / @@ -15,6 +15,7 @@ @@
     import org.elasticsearch.cluster.metadata.IndexMetadata;
     import org.elasticsearch.common.settings.Setting;
     import org.elasticsearch.common.settings.Settings;
+    import org.elasticsearch.features.NodeFeature;
     import org.elasticsearch.index.IndexVersion;
     import org.elasticsearch.index.IndexVersions;
     import org.elasticsearch.index.query.SearchExecutionContext;
@@ Expand Down Expand Up @@
         public static final String NAME = "_inference_fields";
         public static final String CONTENT_TYPE = "_inference_fields";
+        public static final NodeFeature INFERENCE_FIELDS_GET_VIA_SOURCE_INCLUDES = new NodeFeature("inference_fields.get_via_source_includes");
         protected InferenceMetadataFieldsMapper(MappedFieldType inferenceFieldType) {
             super(inferenceFieldType);
         }
@@ Expand Down @@

server/src/main/java/org/elasticsearch/index/mapper/SourceLoader.java

-Original file line number
+Diff line change
@@ Expand Up / @@ -24,7 +24,6 @@ @@
     import java.io.ByteArrayOutputStream;
     import java.io.IOException;
     import java.util.ArrayList;
-    import java.util.LinkedHashMap;
     import java.util.List;
     import java.util.Map;
     import java.util.Set;
@@ Expand Down Expand Up @@
          * @return a new {@link Source} with the patches applied
          */
         static Source applySyntheticVectors(Source originalSource, List<SyntheticVectorPatch> patches) {
-            Map<String, Object> newMap = originalSource.source();
-            // Make sure we have a mutable map, empty implies `Map.of()`
-            if (newMap.isEmpty()) {
-                newMap = new LinkedHashMap<>();
-            }
-            applyPatches("", newMap, patches);
-            return Source.fromMap(newMap, originalSource.sourceContentType());
+            return originalSource.withMutations(map -> applyPatches("", map, patches));
         }
         /**
@@ Expand Down @@

server/src/main/java/org/elasticsearch/search/fetch/subphase/FetchSourcePhase.java

-Original file line number
+Diff line change
@@ Expand Up / @@ -19,7 +19,6 @@ @@
     import org.elasticsearch.search.lookup.Source;
     import org.elasticsearch.search.lookup.SourceFilter;
-    import java.util.HashMap;
     import java.util.Map;
     public final class FetchSourcePhase implements FetchSubPhase {
@@ Expand Down Expand Up @@
                     if (field == null || field.getValues().isEmpty()) {
                         return source;
                     }
-                    var newSource = source.source();
-                    if (newSource instanceof HashMap == false) {
-                        // the map is not mutable
-                        newSource = new HashMap<>(newSource);
-                    }
-                    newSource.put(InferenceMetadataFieldsMapper.NAME, field.getValues().get(0));
-                    return Source.fromMap(newSource, source.sourceContentType());
+                    return source.withMutations(map -> map.put(InferenceMetadataFieldsMapper.NAME, field.getValues().get(0)));
                 }
                 @Override
@@ Expand Down @@

server/src/main/java/org/elasticsearch/search/lookup/Source.java

-Original file line number
+Diff line change
@@ Expand Up / @@ -20,13 +20,21 @@ @@
     import java.io.IOException;
     import java.io.UncheckedIOException;
+    import java.util.HashMap;
+    import java.util.LinkedHashMap;
     import java.util.Map;
+    import java.util.function.Consumer;
     import java.util.function.Supplier;
     /**
-     * The source of a document.  Note that, while objects returned from {@link #source()}
-     * and {@link #internalSourceRef()} are immutable, objects implementing this interface
-     * may not be immutable themselves.
+     * A read-only view of a document's source.
+     *
+     * <p>This interface provides access to source content as either bytes or a parsed map.
+     * A {@code Source} instance represents a stable snapshot of a particular document's
+     * data.
+     *
+     * <p>Note: The Map returned by {@link #source()} may or may not be immutable.
+     * Use {@link #withMutations(Consumer)} for any mutations on the Map returned by {@link #source()}.
      */
     public interface Source {
@@ Expand All / @@ -36,9 +44,12 @@ public interface Source { @@
         XContentType sourceContentType();
         /**
-         * A map representation of the source
-         * <p>
-         * Important: This can lose precision on numbers with a decimal point. It
+         * A map representation of the source.
+         *
+         * <p><b>IMPORTANT</b>: The returned map may be immutable. To modify the source,
+         * use {@link #withMutations(java.util.function.Consumer)} instead.
+         *
+         * <p>This can lose precision on numbers with a decimal point. It
          * converts numbers like {@code "n": 1234.567} to a {@code double} which
          * only has 52 bits of precision in the mantissa. This will come up most
          * frequently when folks write nanosecond precision dates as a decimal
@@ Expand All / @@ -56,6 +67,37 @@ public interface Source { @@
          */
         Source filter(SourceFilter sourceFilter);
+        /**
+         * Returns a new Source with mutations applied to the map.
+         *
+         * <p>Use this when you need to add, remove, or update fields on a map that may or may
+         * not be mutable.
+         *
+         * <p><b>WARNING</b>: If the underlying source map is already a {@link java.util.HashMap}
+         * (including {@link java.util.LinkedHashMap}), the original map will be mutated directly
+         * rather than copied. This is intentional for performance, but callers should be aware
+         * that the original Source's map may be modified as a side effect.
+         *
+         * <pre>
+         *   Source modified = source.withMutations(map -&gt; map.put("field", "value"));
+         * </pre>
+         *
+         * @param mutator a function that modifies the map
+         * @return a new Source with the mutations applied. There is no guarantee about the mutability of the returned value's source() map.
+         */
+        default Source withMutations(java.util.function.Consumer<Map<String, Object>> mutator) {
+            Map<String, Object> map = source();
+            if (map == null) {
+                map = new LinkedHashMap<>();
+            } else if (map instanceof HashMap == false) {
+                // bit of a hack to test for mutability...there aren't great options
+                map = new LinkedHashMap<>(map);
+            }
+            mutator.accept(map);
+            return Source.fromMap(map, sourceContentType());
+        }
         /**
          * For the provided path, return its value in the source.
          *
@@ Expand Down @@

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