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  1. Apache Arrow
  2. ARROW-462

[C++] Implement in-memory conversions between non-nested primitive types and DictionaryArray equivalent

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Details

    • New Feature
    • Status: Resolved
    • Major
    • Resolution: Fixed
    • None
    • 0.5.0
    • C++
    • None

    Description

      We use a hash table to extract unique values and dictionary indices. There may be an opportunity to consolidate common code from the dictionary encoding implementation implemented in parquet-cpp (but the dictionary indices will not be run-length encoded in Arrow):

      https://github.com/apache/parquet-cpp/blob/master/src/parquet/encodings/dictionary-encoding.h

      This functionality also needs to permit encoding split across multiple record batches – so the hash table would be a stateful entity, and we can continue to hash more chunks of data to dictionary-encode multiple arrays with a shared dictionary at the end.

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            uwe Uwe Korn
            wesm Wes McKinney
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              Created:
              Updated:
              Resolved: