[GitHub] [arrow] wesm commented on a change in pull request #8050: ARROW-9852: [C++] Validate dictionaries fully on IPC read

[GitBox <gi...@apache.org>]

wesm commented on a change in pull request #8050:
URL: https://github.com/apache/arrow/pull/8050#discussion_r476727957



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File path: cpp/src/arrow/ipc/reader.cc
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@@ -717,8 +717,10 @@ Status ReadDictionary(const Buffer& metadata, DictionaryMemo* dictionary_memo,
     return Status::Invalid("Dictionary record batch must only contain one field");
   }
   auto dictionary = batch->column(0);
-  // Validate the dictionary for safe delta concatenation
-  RETURN_NOT_OK(dictionary->Validate());
+  // Validate the dictionary for safe delta concatenation.  Full validation
+  // is necessary for certain types (for example nested dictionaries).
+  // XXX: instead only validate when a concatenation is actually done?
+  RETURN_NOT_OK(dictionary->ValidateFull());

Review comment:
       Could this be deferred until the actual time that the delta must be applied? That seems better but I'm OK with this if a stopgap is needed




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