Struct arrow::array::UnionBuilder

pub struct UnionBuilder { /* private fields */ }

Builder type for creating a new UnionArray.

Example: Dense Memory Layout

use arrow::array::UnionBuilder;
use arrow::datatypes::{Float64Type, Int32Type};

let mut builder = UnionBuilder::new_dense(3);
builder.append::<Int32Type>("a", 1).unwrap();
builder.append::<Float64Type>("b", 3.0).unwrap();
builder.append::<Int32Type>("a", 4).unwrap();
let union = builder.build().unwrap();

assert_eq!(union.type_id(0), 0_i8);
assert_eq!(union.type_id(1), 1_i8);
assert_eq!(union.type_id(2), 0_i8);

assert_eq!(union.value_offset(0), 0_i32);
assert_eq!(union.value_offset(1), 0_i32);
assert_eq!(union.value_offset(2), 1_i32);

Example: Sparse Memory Layout

use arrow::array::UnionBuilder;
use arrow::datatypes::{Float64Type, Int32Type};

let mut builder = UnionBuilder::new_sparse(3);
builder.append::<Int32Type>("a", 1).unwrap();
builder.append::<Float64Type>("b", 3.0).unwrap();
builder.append::<Int32Type>("a", 4).unwrap();
let union = builder.build().unwrap();

assert_eq!(union.type_id(0), 0_i8);
assert_eq!(union.type_id(1), 1_i8);
assert_eq!(union.type_id(2), 0_i8);

assert_eq!(union.value_offset(0), 0_i32);
assert_eq!(union.value_offset(1), 1_i32);
assert_eq!(union.value_offset(2), 2_i32);

Implementations

impl UnionBuilder

pub fn new_dense(capacity: usize) -> Self

Creates a new dense array builder.

pub fn new_sparse(capacity: usize) -> Self

Creates a new sparse array builder.

pub fn append_null<T: ArrowPrimitiveType>(
    &mut self,
    type_name: &str
) -> Result<()>

Appends a null to this builder, encoding the null in the array of the type_name child / field.

Since UnionArray encodes nulls as an entry in its children (it doesn’t have a validity bitmap itself), and where the null is part of the final array, appending a NULL requires specifying which field (child) to use.

pub fn append<T: ArrowPrimitiveType>(
    &mut self,
    type_name: &str,
    v: T::Native
) -> Result<()>

Appends a value to this builder.

pub fn build(self) -> Result<UnionArray>

Builds this builder creating a new UnionArray.

Trait Implementations

impl Debug for UnionBuilder

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.