liyafan82 commented on a change in pull request #7544:
URL: https://github.com/apache/arrow/pull/7544#discussion_r448166650



##########
File path: cpp/src/arrow/ipc/reader.cc
##########
@@ -684,7 +685,19 @@ Status ReadDictionary(const Buffer& metadata, 
DictionaryMemo* dictionary_memo,
     return Status::Invalid("Dictionary record batch must only contain one 
field");
   }
   auto dictionary = batch->column(0);
-  return dictionary_memo->AddDictionary(id, dictionary);
+  if (dictionary_batch->isDelta()) {
+    std::shared_ptr<Array> originalDict, combinedDict;
+    RETURN_NOT_OK(dictionary_memo->GetDictionary(id, &originalDict));
+    ArrayVector dictsToCombine{originalDict, dictionary};
+    ARROW_ASSIGN_OR_RAISE(combinedDict, Concatenate(dictsToCombine, 
options.memory_pool));
+    return dictionary_memo->UpdateDictionary(id, combinedDict);
+  }
+
+  if (dictionary_memo->HasDictionary(id)) {

Review comment:
       Thanks for the good suggestion. I have added the AddOrReplaceDictionary 
method. 




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