Uploaded image for project: 'Apache Arrow'
  1. Apache Arrow
  2. ARROW-56

Format: Specify LSB bit ordering in bit arrays

    Details

    • Type: New Feature
    • Status: Resolved
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 0.1.0
    • Component/s: Format
    • Labels:
      None

      Description

      In https://github.com/apache/arrow/blob/master/format/Layout.md, we describe bitmaps for nulls (presumably same encoding for boolean data) and provide the C code for accessing a bit:

      bitmask[j / 8] & (1 << (j % 8))

      Implicitly this is LSB bit-endianness (https://en.wikipedia.org/wiki/Bit_numbering) – see the discussion of bitpacking in the Parquet format: https://github.com/apache/parquet-format/blob/master/Encodings.md#run-length-encoding--bit-packing-hybrid-rle--3

      If this is what we want, we should make this aspect of the format explicit.

        Attachments

          Activity

            People

            • Assignee:
              wesmckinn Wes McKinney
              Reporter:
              wesmckinn Wes McKinney
            • Votes:
              0 Vote for this issue
              Watchers:
              1 Start watching this issue

              Dates

              • Created:
                Updated:
                Resolved: