Fix match_only_text for keyword multi-fields with doc values and ignore above

Author: jordan-powers

modules/mapper-extras/src/main/java/org/elasticsearch/index/mapper/extras/MatchOnlyTextFieldMapper.java

@@ -253,11 +253,18 @@ private IOFunction<LeafReaderContext, CheckedIntFunction<List<Object>, IOExcepti
             if (searchExecutionContext.isSourceSynthetic() && withinMultiField) {
                 String parentField = searchExecutionContext.parentPath(name());
                 var parent = searchExecutionContext.lookup().fieldType(parentField);
-                if (parent.isStored()) {
-                    if (parent instanceof KeywordFieldMapper.KeywordFieldType keywordParent
-                        && keywordParent.ignoreAbove() != Integer.MAX_VALUE) {
+
+                if (parent instanceof KeywordFieldMapper.KeywordFieldType keywordParent
+                    && keywordParent.ignoreAbove() != Integer.MAX_VALUE) {
+                    if (parent.isStored()) {
                         return storedFieldFetcher(parentField, keywordParent.originalName());
+                    } else if (parent.hasDocValues()) {
+                        var ifd = searchExecutionContext.getForField(parent, MappedFieldType.FielddataOperation.SEARCH);
+                        return combineFieldFetchers(docValuesFieldFetcher(ifd), storedFieldFetcher(keywordParent.originalName()));
                     }
+                }
+
+                if (parent.isStored()) {
                     return storedFieldFetcher(parentField);
                 } else if (parent.hasDocValues()) {
                     var ifd = searchExecutionContext.getForField(parent, MappedFieldType.FielddataOperation.SEARCH);
@@ -268,14 +275,21 @@ private IOFunction<LeafReaderContext, CheckedIntFunction<List<Object>, IOExcepti
             } else if (searchExecutionContext.isSourceSynthetic() && hasCompatibleMultiFields) {
                 var mapper = (MatchOnlyTextFieldMapper) searchExecutionContext.getMappingLookup().getMapper(name());
                 var kwd = TextFieldMapper.SyntheticSourceHelper.getKeywordFieldMapperForSyntheticSource(mapper);
+
                 if (kwd != null) {
                     var fieldType = kwd.fieldType();
-                    if (fieldType.isStored()) {
-                        if (fieldType.ignoreAbove() != Integer.MAX_VALUE) {
+
+                    if (fieldType.ignoreAbove() != Integer.MAX_VALUE) {
+                        if (fieldType.isStored()) {
                             return storedFieldFetcher(fieldType.name(), fieldType.originalName());
-                        } else {
-                            return storedFieldFetcher(fieldType.name());
+                        } else if (fieldType.hasDocValues()) {
+                            var ifd = searchExecutionContext.getForField(fieldType, MappedFieldType.FielddataOperation.SEARCH);
+                            return combineFieldFetchers(docValuesFieldFetcher(ifd), storedFieldFetcher(fieldType.originalName()));
                         }
+                    }
+
+                    if (fieldType.isStored()) {
+                        return storedFieldFetcher(fieldType.name());
                     } else if (fieldType.hasDocValues()) {
                         var ifd = searchExecutionContext.getForField(fieldType, MappedFieldType.FielddataOperation.SEARCH);
                         return docValuesFieldFetcher(ifd);
@@ -337,6 +351,32 @@ private static IOFunction<LeafReaderContext, CheckedIntFunction<List<Object>, IO
             };
         }
 
+        private static IOFunction<LeafReaderContext, CheckedIntFunction<List<Object>, IOException>> combineFieldFetchers(
+            IOFunction<LeafReaderContext, CheckedIntFunction<List<Object>, IOException>> primaryFetcher,
+            IOFunction<LeafReaderContext, CheckedIntFunction<List<Object>, IOException>> secondaryFetcher
+        ) {
+            return context -> {
+                var primaryGetter = primaryFetcher.apply(context);
+                var secondaryGetter = secondaryFetcher.apply(context);
+                return docId -> {
+                    List<Object> values = new ArrayList<>();
+                    var primary = primaryGetter.apply(docId);
+                    if (primary != null) {
+                        values.addAll(primary);
+                    }
+
+                    var secondary = secondaryGetter.apply(docId);
+                    if (secondary != null) {
+                        values.addAll(secondary);
+                    }
+
+                    assert primary != null || secondary != null;
+
+                    return values;
+                };
+            };
+        }
+
         private Query toQuery(Query query, SearchExecutionContext searchExecutionContext) {
             return new ConstantScoreQuery(
                 new SourceConfirmedTextQuery(query, getValueFetcherProvider(searchExecutionContext), indexAnalyzer)