[jira] [Created] (ARROW-661) [C++] Add a Flatbuffer metadata type that supports array data over 2^31 - 1 elements

["Wes McKinney (JIRA)" <ji...@apache.org>]

Wes McKinney created ARROW-661:
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             Summary: [C++] Add a Flatbuffer metadata type that supports array data over 2^31 - 1 elements
                 Key: ARROW-661
                 URL: https://issues.apache.org/jira/browse/ARROW-661
             Project: Apache Arrow
          Issue Type: New Feature
          Components: C++
            Reporter: Wes McKinney


Users of Arrow C++ have reported needing to store large arrays using our shared memory IPC machinery. While data over 2^31 - 1 elements is "out of spec" as far as what it means to "implement Arrow", it would be useful to have a "LargeRecordBatch" type that permits storing large arrays. Other Arrow implementations in general will not need to support reading and writing this data -- this is closely related to the tensor discussion in ARROW-550.

{code}
struct LargeFieldNode {
  length: long;
  null_count: long;
}

table LargeRecordBatch {
  length: long;
  nodes: [LargeFieldNode];
  buffers: [Buffer];
}
{code}

An initial implementation of this will be marked experimental so that we can get the code into the hands of users (like the Ray project https://github.com/ray-project/ray) in case there's some ongoing discussion to be had about handling very large vectors/arrays.

Reading and writing this metadata should be achievable without a huge amount of code duplication, I will see what I can do. 



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