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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2021/04/28 09:27:01 UTC

[GitHub] [arrow] pitrou commented on a change in pull request #10174: ARROW-12554: [C++] Allow duplicates in `SetLookupOptions::value_set`

pitrou commented on a change in pull request #10174:
URL: https://github.com/apache/arrow/pull/10174#discussion_r621993183



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File path: cpp/src/arrow/compute/kernels/scalar_set_lookup.cc
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@@ -75,6 +95,9 @@ struct SetLookupState : public KernelState {
 
   using MemoTable = typename HashTraits<Type>::MemoTableType;
   MemoTable lookup_table;
+  // When there are duplicates in value_set, the MemoTable indices must
+  // be mapped back to indices in the value_set.
+  std::vector<int32_t> memo_index_to_value_index;

Review comment:
       We would some lose performance in exchange of a little space saving. The hash table is much larger, I don't think this is desirable.




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