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Signed-off-by: panguixin <[email protected]>

Author: bugmakerrrrrr

CHANGELOG.md

@@ -30,7 +30,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Introduce framework for auxiliary transports and an experimental gRPC transport plugin ([#16534](https://github.com/opensearch-project/OpenSearch/pull/16534))
 - Changes to support IP field in star tree indexing([#16641](https://github.com/opensearch-project/OpenSearch/pull/16641/))
 - Support object fields in star-tree index([#16728](https://github.com/opensearch-project/OpenSearch/pull/16728/))
-- Optimize flat_object type in a BWC way with one phase processing ([#16297](https://github.com/opensearch-project/OpenSearch/pull/16297))
+- Improve flat_object field parsing performance by reducing two passes to a single pass ([#16297](https://github.com/opensearch-project/OpenSearch/pull/16297))
 
 ### Dependencies
 - Bump `com.google.cloud:google-cloud-core-http` from 2.23.0 to 2.47.0 ([#16504](https://github.com/opensearch-project/OpenSearch/pull/16504))

server/src/main/java/org/opensearch/index/mapper/FlatObjectFieldMapper.java

@@ -604,11 +604,10 @@ private void createPathFields(ParseContext context, HashSet<String> pathParts) {
             if (fieldType.indexOptions() != IndexOptions.NONE || fieldType.stored()) {
                 context.doc().add(new Field(name(), value, fieldType));
             }
-            if (fieldType().hasDocValues() == false && fieldType.omitNorms()) {
-                createFieldNamesField(context);
-            }
             if (fieldType().hasDocValues()) {
                 context.doc().add(new SortedSetDocValuesField(name(), value));
+            } else {
+                createFieldNamesField(context);
             }
         }
     }