Struct List 

pub struct List<T>(/* private fields */);

Wrapper denoting an Arrow ListArray column with elements of T.

Notes:

• List-level nullability: wrap the column in Option<List<T>>.
• Item-level nullability: use List<Option<T>> when elements can be null.

Implementations

impl<T> List<T>

pub fn new(values: Vec<T>) -> Self

Construct a new list from a vector of values.

Examples found in repository

examples/02_lists.rs (line 22)

fn main() {
    // DataTypes from compile-time mapping
    println!(
        "tags={:?}, scores={:?}",
        <Row as ColAt<0>>::data_type(),
        <Row as ColAt<1>>::data_type()
    );

    // Build a List<Utf8> column manually via ArrowBinding
    let mut lb = <List<String> as ArrowBinding>::new_builder(2);
    <List<String> as ArrowBinding>::append_value(&mut lb, &List::new(vec!["a".into(), "b".into()]));
    <List<String> as ArrowBinding>::append_value(&mut lb, &List::new(vec!["x".into()]));
    let la = <List<String> as ArrowBinding>::finish(lb);
    println!(
        "List<Utf8> len={}, first_list_len={}",
        la.len(),
        arrow_array::cast::as_list_array(&la).value_length(0)
    );

    // Build a nullable-list of nullable i32 items
    let mut nullable_builder = <List<Option<i32>> as ArrowBinding>::new_builder(2);
    <List<Option<i32>> as ArrowBinding>::append_value(
        &mut nullable_builder,
        &List::new(vec![Some(1), None]),
    );
    <List<Option<i32>> as ArrowBinding>::append_null(&mut nullable_builder);
    let nullable_arr = <List<Option<i32>> as ArrowBinding>::finish(nullable_builder);
    println!(
        "List<Nullable<i32>> len={}, second_is_null={}",
        nullable_arr.len(),
        nullable_arr.is_null(1)
    );
}

pub fn values(&self) -> &Vec<T>

Borrow the underlying values.

pub fn into_inner(self) -> Vec<T>

Consume and return the underlying vector of values.

Trait Implementations

impl<T> ArrowBinding for List<Option<T>>

where T: ArrowBinding, <T as ArrowBinding>::Builder: ArrayBuilder,

Provide ArrowBinding for List<Option<T>> so users can express item-nullability via Option in the type parameter.

type Builder = GenericListBuilder<i32, <T as ArrowBinding>::Builder>

Concrete Arrow builder type used for this Rust type.

type Array = GenericListArray<i32>

Concrete Arrow array type produced by finish.

fn data_type() -> DataType

The Arrow DataType corresponding to this Rust type.

fn new_builder(_capacity: usize) -> Self::Builder

Create a new builder with an optional capacity hint.

fn append_value(b: &mut Self::Builder, v: &Self)

Append a non-null value to the builder.

fn append_null(b: &mut Self::Builder)

Append a null to the builder.

fn finish(b: Self::Builder) -> Self::Array

Finish the builder and produce a typed Arrow array.

impl<T> ArrowBinding for List<T>

where T: ArrowBinding, <T as ArrowBinding>::Builder: ArrayBuilder,

type Builder = GenericListBuilder<i32, <T as ArrowBinding>::Builder>

Concrete Arrow builder type used for this Rust type.

type Array = GenericListArray<i32>

Concrete Arrow array type produced by finish.

fn data_type() -> DataType

The Arrow DataType corresponding to this Rust type.

fn new_builder(_capacity: usize) -> Self::Builder

Create a new builder with an optional capacity hint.

fn append_value(b: &mut Self::Builder, v: &Self)

Append a non-null value to the builder.

fn append_null(b: &mut Self::Builder)

Append a null to the builder.

fn finish(b: Self::Builder) -> Self::Array

Finish the builder and produce a typed Arrow array.

impl<T> From<Vec<T>> for List<T>

fn from(values: Vec<T>) -> Self

Convert a vector into a List<T>.

impl<T> FromIterator<T> for List<T>

fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self

Collect an iterator into a List<T>.