[jira] [Created] (ARROW-13599) [C++] [Dataset] Add optional scan type that tags batches with locational information

["Weston Pace (Jira)" <ji...@apache.org>]

Weston Pace created ARROW-13599:
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             Summary: [C++] [Dataset] Add optional scan type that tags batches with locational information
                 Key: ARROW-13599
                 URL: https://issues.apache.org/jira/browse/ARROW-13599
             Project: Apache Arrow
          Issue Type: Improvement
          Components: C++
            Reporter: Weston Pace


Currently there are two types of scans:

 * Ordered scan - Yields batches in order (includes batch index and fragment index)
 * Unordered scan - Yields batches in any order (no batch index or fragment index)

There is a third type of scan (Tagged scan?  Indexed scan?) which could tag each batch with the starting row # of the batch.  Certain file types (like parquet & IPC) should be able to support this with similar performance to an unordered scan (since the # of rows is in the metadata).

Other file types (like CSV) could fall back to an ordered scan or do something like a two pass approach to count the # of newlines in a file and then scan the file itself (not sure if this makes sense yet).



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