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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2021/01/12 02:12:59 UTC

[GitHub] [arrow] westonpace edited a comment on pull request #8984: ARROW-5336: [C++] Implement arrow::Concatenate for dictionary-encoded arrays with unequal dictionaries

westonpace edited a comment on pull request #8984:
URL: https://github.com/apache/arrow/pull/8984#issuecomment-758347141


   @jorisvandenbossche It's pretty close but there are a few differences.
   
   - The pandas code allows the index type to expand (e.g. from uint8_t to uint16_t).  In fact, it looks like it always sets it to int32_t.  Also, arrow doesn't allow dictionary indices to be negative.
   - The pandas code puts -1 in the map for a null value.  Arrow uses null in the validity bitmap for the indices array and/or null as an item in the dictionary itself with a valid index (both arrow approaches are legal but the pandas approach is neither of those)
   
   I'll defer to @pitrou if we want to combine them but it seems simpler to just leave them separate for now.


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