Function polars::export::arrow::io::parquet::read::read_columns_many_async

pub async fn read_columns_many_async<'a, 'b, R, F>(
    factory: F, 
    row_group: &'_ RowGroupMetaData, 
    fields: Vec<Field, Global>, 
    chunk_size: Option<usize>
) -> Result<Vec<Box<dyn Iterator<Item = Result<Arc<dyn Array + 'static>, ArrowError>> + Send + Sync + 'a, Global>, Global>, ArrowError> where
    R: AsyncRead + AsyncSeek + Send + Unpin,
    F: Fn() -> Pin<Box<dyn Future<Output = Result<R, Error>> + Send + 'b, Global>> + Clone, 

This is supported on crate feature io_parquet only.

Returns a vector of iterators of Array corresponding to the top level parquet fields whose name matches fields’s names.

This operation is IO-bounded O(C) where C is the number of columns in the row group - it reads all the columns to memory from the row group associated to the requested fields.

Implementation

This operation is IO-bounded O(C) where C is the number of columns in the row group - it reads all the columns to memory from the row group associated to the requested fields. It does so asynchronously via join_all