[GitHub] [arrow] jorgecarleitao commented on pull request #9090: ARROW-11123: [Rust] Use cast kernel to simplify csv parser

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jorgecarleitao commented on pull request #9090:
URL: https://github.com/apache/arrow/pull/9090#issuecomment-754084930


   I'm curious about the perf implications. Even for integers or dates, we will always need to verify that they are utf8 compliant to create valid `StringArray` value buffers. We could store then as `BinaryArray` instead. My hypothesis is that most of the `to_str / to_datetime / to_int` are not SIMDed and thus unlikely to benefit from Arrow, but it could also be that the columnar format helps the compiler.
   
   Note that people can always pass a `DataType::Utf8` to the schema instead of inferring it and cast the types themselves. I always understood the readers (csv, json, parquet) as ways to bypass that approach and create Arrow arrays directly from the format. It happens that CSV is a particularly poor format for this, as everything is a (not-necessarily utf8) string with very little invariants.
   


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