Function arrow2::io::parquet::write::transverse

source · [−]

pub fn transverse<T, F: Fn(&DataType) -> T + Clone>(
    data_type: &DataType,
    map: F
) -> Vec<T>ⓘNotable traits for Vec<u8, A>impl<A> Write for Vec<u8, A> where
    A: Allocator,

Available on crate feature io_parquet only.

Expand description

Transverses the data_type up to its (parquet) columns and returns a vector of items based on map. This is used to assign an Encoding to every parquet column based on the columns’ type (see example)

Example

use arrow2::io::parquet::write::{transverse, Encoding};
use arrow2::datatypes::{DataType, Field};

let dt = DataType::Struct(vec![
    Field::new("a", DataType::Int64, true),
    Field::new("b", DataType::List(Box::new(Field::new("item", DataType::Int32, true))), true),
]);

let encodings = transverse(&dt, |dt| Encoding::Plain);
assert_eq!(encodings, vec![Encoding::Plain, Encoding::Plain]);