[jira] [Created] (ARROW-11618) [Rust] [Parquet] String-based path column projection

["Neville Dipale (Jira)" <ji...@apache.org>]

Neville Dipale created ARROW-11618:
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             Summary: [Rust] [Parquet] String-based path column projection
                 Key: ARROW-11618
                 URL: https://issues.apache.org/jira/browse/ARROW-11618
             Project: Apache Arrow
          Issue Type: Task
          Components: Rust
            Reporter: Neville Dipale


There is currently no way to select a column by its path, e.g. 'a.b.c'. We have to select the column by its index, which is not trivial for nested structures.

For example, if a record has the following schema, the column indices are shown in parentheses:

{code}
schema:
  a [struct]         ("a")        
    b [struct]       ("a.b")      
      c [int32]      ("a.b.c")    
      d [struct]     ("a.b.d")    
        e [int32]    ("a.b.d.e")  [0]
        f [bool]     ("a.b.d.f")  [1]
      g [int64]      ("a.b.g")    [2]
{code}

if one wants to select 'a.b', they need to know that 'a.b' spans 3 (0 to 2) columns. This is inconvenient, and potentially forces readers to read whole records to avoid this inconvenience.

A string-based projection could allow one to select columns 0 and 1 via "a.b.d" or column 2 via "a.b.g"



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