[GitHub] [arrow-rs] wjones127 opened a new issue, #3764: Common trait for RecordBatch and StructArray

["wjones127 (via GitHub)" <gi...@apache.org>]

wjones127 opened a new issue, #3764:
URL: https://github.com/apache/arrow-rs/issues/3764

   **Is your feature request related to a problem or challenge? Please describe what you are trying to do.**
   
   I wanted to write some code that was generic over `StructArray` and `RecordBatch`, but it appears they don't have the same traits (although they are easily convertible).
   
   It seems like there are many shared methods that could be brought into a common trait:
   
    * `column()`
    * `column_by_name()`
    * `columns()`
    * `num_columns()`
    * `num_rows()`
   
   **Describe the solution you'd like**
   
   I'd propose a trait `ArrowTabular` that has these methods.
   
   **Describe alternatives you've considered**
   
   I'm open to alternatives, but couldn't think of any. In any case, I'm implementing a trait for my own use case and if folks are open to this I could upstream it into arrow-rs.
   
   **Additional context**
   
   For context, the thing I am trying to implement is:
   
   ```rust
   /// Represents a row in an [ArrowTabular].
   #[derive(Debug, Clone, Copy)]
   struct RowReference<'a, T: ArrowTabular + 'a> {
       pub inner: &'a T,
       pub pos: usize
   }
   
   impl<'a, T: ArrowTabular + 'a> RowReference<'a, T> {
       fn get_str(&'a self, col_i: usize) -> Option<&'a str> {
           let column = as_string_array(self.inner.column(col_i));
           if column.is_null(self.pos) {
               None
           } else {
               Some(column.value(self.pos))
           }
       }
   }
   ```
   
   This is to help navigate the highly nested schema in [ADBC's GetObjects output](https://github.com/apache/arrow-adbc/blob/e79edafdb02339664ea735097f8c1edc0ea052de/adbc.h#L815), where an entry might be a row of a record batch or a row in a struct array, depending on which level you are at.


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[GitHub] [arrow-rs] tustvold closed issue #3764: Common trait for RecordBatch and StructArray

["tustvold (via GitHub)" <gi...@apache.org>]

tustvold closed issue #3764: Common trait for RecordBatch and StructArray
URL: https://github.com/apache/arrow-rs/issues/3764


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[GitHub] [arrow-rs] tustvold commented on issue #3764: Common trait for RecordBatch and StructArray

["tustvold (via GitHub)" <gi...@apache.org>]

tustvold commented on issue #3764:
URL: https://github.com/apache/arrow-rs/issues/3764#issuecomment-1445303228

   The way that the parquet reader, etc...handle this is to just use StructArray and convert to/from RecordBatch where necessary. Perhaps that would work for your use-case without adding complexity? Generics, especially recursive ones, get painfuo quickly 😅


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[GitHub] [arrow-rs] wjones127 commented on issue #3764: Common trait for RecordBatch and StructArray

["wjones127 (via GitHub)" <gi...@apache.org>]

wjones127 commented on issue #3764:
URL: https://github.com/apache/arrow-rs/issues/3764#issuecomment-1445408036

   I see. If I convert the top-level to `StructArray`, then it's `StructArray` all the way down! That seems like a reasonable simplification. 👍 


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