Struct arrow_array::builder::UnionBuilder

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pub struct UnionBuilder { /* private fields */ }

Expand description

Builder type for creating a new 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_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


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_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§

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impl UnionBuilder

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pub fn new_dense() -> Self

Creates a new dense array builder.

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pub fn new_sparse() -> Self

Creates a new sparse array builder.

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pub fn with_capacity_dense(capacity: usize) -> Self

Creates a new dense array builder with capacity.

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pub fn with_capacity_sparse(capacity: usize) -> Self

Creates a new sparse array builder with capacity.

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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.

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