Make deleteByQuery protected and remove built-in flush

Author: bcully

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

@@ -3612,10 +3612,8 @@ protected long estimateMergeBytes(MergePolicy.OneMerge merge) {
         }
     }
 
-    public void deleteByQuery(ShardSplittingQuery query) throws Exception {
-        // System.out.println("Delete documents using ShardSplitQuery");
+    // Used to clean up unowned documents. Client-visible deletes should always be soft deletes.
+    protected void deleteByQuery(ShardSplittingQuery query) throws Exception {
         indexWriter.deleteDocuments(query);
-        indexWriter.flush();
-        indexWriter.commit();
     }
 }