Struct UnionBuilder

pub struct UnionBuilder {
    len: usize,
    fields: BTreeMap<String, FieldData>,
    type_id_builder: Int8BufferBuilder,
    value_offset_builder: Option<Int32BufferBuilder>,
    initial_capacity: usize,
}

Builder for UnionArray

Example: Dense Memory Layout

let mut builder = UnionBuilder::new_dense();
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);
assert_eq!(union.type_id(1), 1);
assert_eq!(union.type_id(2), 0);

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

Example: Sparse Memory Layout

let mut builder = UnionBuilder::new_sparse();
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);
assert_eq!(union.type_id(1), 1);
assert_eq!(union.type_id(2), 0);

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

Fields

len: usize

The current number of slots in the array

fields: BTreeMap<String, FieldData>

Maps field names to FieldData instances which track the builders for that field

type_id_builder: Int8BufferBuilder

Builder to keep track of type ids

value_offset_builder: Option<Int32BufferBuilder>

Builder to keep track of offsets (None for sparse unions)

initial_capacity: usize

Implementations

impl UnionBuilder

pub fn new_dense() -> Self

Creates a new dense array builder.

pub fn new_sparse() -> Self

Creates a new sparse array builder.

pub fn with_capacity_dense(capacity: usize) -> Self

Creates a new dense array builder with capacity.

pub fn with_capacity_sparse(capacity: usize) -> Self

Creates a new sparse array builder with capacity.

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

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<(), ArrowError>

Appends a value to this builder.

fn append_option<T: ArrowPrimitiveType>( &mut self, type_name: &str, v: Option<T::Native>, ) -> Result<(), ArrowError>

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

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.