Revert "Nullify sourceAsMap once a search hit is processed (#119734)" (#119751)

This reverts commit ab77144.

Author: iverase

server/src/main/java/org/elasticsearch/search/SearchHit.java

@@ -491,13 +491,6 @@ public Map<String, Object> getSourceAsMap() {
         return sourceAsMap;
     }
 
-    /**
-     * Set the cache document as a map to {@code null}.
-     */
-    public void resetSourceAsMap() {
-        sourceAsMap = null;
-    }
-
     /**
      * The hit field matching the given field name.
      */
@@ -735,7 +728,6 @@ private void deallocate() {
         if (SearchHit.this.source instanceof RefCounted r) {
             r.decRef();
         }
-        SearchHit.this.sourceAsMap = null;
         SearchHit.this.source = null;
     }
 

server/src/main/java/org/elasticsearch/search/fetch/FetchPhaseDocsIterator.java

@@ -86,10 +86,7 @@ public final SearchHit[] iterate(
                     }
                     currentDoc = docs[i].docId;
                     assert searchHits[docs[i].index] == null;
-                    SearchHit searchHit = nextDoc(docs[i].docId);
-                    // free some memory
-                    searchHit.resetSourceAsMap();
-                    searchHits[docs[i].index] = searchHit;
+                    searchHits[docs[i].index] = nextDoc(docs[i].docId);
                 } catch (ContextIndexSearcher.TimeExceededException e) {
                     if (allowPartialResults == false) {
                         purgeSearchHits(searchHits);