Struct ListArray 

pub struct ListArray { /* private fields */ }

A list array that stores variable-length lists of elements, similar to Vec<Vec<T>>.

This mirrors the Apache Arrow List array encoding and provides efficient storage for nested data where each row contains a list of elements of the same type.

Data Layout

The list array uses an offset-based encoding:

• Elements array: A flat array containing all list elements concatenated together
• Offsets array: Integer array where offsets[i] is an (inclusive) start index into the elements and offsets[i+1] is the (exclusive) stop index for the ith list.
• Validity: Optional mask indicating which lists are null

This allows for excellent cascading compression of the elements and offsets, as similar values are clustered together and the offsets have a predictable pattern and small deltas between consecutive elements.

Offset Semantics

• Offsets must be non-nullable integers (i32, i64, etc.)
• Offsets array has length n+1 where n is the number of lists
• List i contains elements from elements[offsets[i]..offsets[i+1]]
• Offsets must be monotonically increasing

Examples

use vortex_array::arrays::{ListArray, PrimitiveArray};
use vortex_array::validity::Validity;
use vortex_array::IntoArray;
use vortex_buffer::buffer;
use std::sync::Arc;

// Create a list array representing [[1, 2], [3, 4, 5], []]
let elements = buffer![1i32, 2, 3, 4, 5].into_array();
let offsets = buffer![0u32, 2, 5, 5].into_array(); // 3 lists

let list_array = ListArray::try_new(
    elements.into_array(),
    offsets.into_array(),
    Validity::NonNullable,
).unwrap();

assert_eq!(list_array.len(), 3);

// Access individual lists
let first_list = list_array.list_elements_at(0);
assert_eq!(first_list.len(), 2); // [1, 2]

let third_list = list_array.list_elements_at(2);
assert!(third_list.is_empty()); // []

Implementations

impl ListArray

pub fn new(elements: ArrayRef, offsets: ArrayRef, validity: Validity) -> Self

Creates a new ListArray.

Panics

Panics if the provided components do not satisfy the invariants documented in ListArray::new_unchecked.

pub fn try_new( elements: ArrayRef, offsets: ArrayRef, validity: Validity, ) -> VortexResult<Self>

Constructs a new ListArray.

See ListArray::new_unchecked for more information.

Errors

Returns an error if the provided components do not satisfy the invariants documented in ListArray::new_unchecked.

pub unsafe fn new_unchecked( elements: ArrayRef, offsets: ArrayRef, validity: Validity, ) -> Self

Creates a new ListArray without validation from these components:

• elements is a flat array containing all list elements concatenated.
• offsets is an integer array where offsets[i] is the start index for list i.
• validity holds the null values.

Safety

The caller must ensure all of the following invariants are satisfied:

• Offsets must be a non-nullable integer array.
• Offsets must have at least one element (even for empty lists, it should contain [0]).
• Offsets must be sorted (monotonically increasing).
• All offset values must be non-negative.
• The maximum offset must not exceed elements.len().
• If validity is an array, its length must equal offsets.len() - 1.

pub fn offset_at(&self, index: usize) -> usize

Returns the offset at the given index from the list array.

Panics if the index is out of bounds.

pub fn list_elements_at(&self, index: usize) -> ArrayRef

Returns the elements of the list scalar at the given index of the list array.

pub fn sliced_elements(&self) -> ArrayRef

Returns elements of the list array referenced by the offsets array.

This is useful for discarding any potentially unused parts of the underlying elements child array.

pub fn offsets(&self) -> &ArrayRef

Returns the offsets array.

pub fn elements(&self) -> &ArrayRef

Returns the elements array.

pub fn reset_offsets(&self) -> VortexResult<Self>

Create a copy of this array by adjusting offsets to start at 0 and removing elements not referenced by the offsets.

impl ListArray

pub fn from_iter_slow<O: OffsetPType, I: IntoIterator>( iter: I, dtype: Arc<DType>, ) -> VortexResult<ArrayRef>

where I::Item: IntoIterator, <I::Item as IntoIterator>::Item: Into<Scalar>,

This is a convenience method to create a list array from an iterator of iterators. This method is slow however since each element is first converted to a scalar and then appended to the array.

pub fn from_iter_opt_slow<O: OffsetPType, I: IntoIterator<Item = Option<T>>, T>( iter: I, dtype: Arc<DType>, ) -> VortexResult<ArrayRef>

where T: IntoIterator, T::Item: Into<Scalar>,

Methods from Deref<Target = dyn Array>

pub fn display_values(&self) -> impl Display

Display logical values of the array

For example, an i16 typed array containing the first five non-negative integers is displayed as: [0i16, 1i16, 2i16, 3i16, 4i16].

Examples

let array = buffer![0_i16, 1, 2, 3, 4].into_array();
assert_eq!(
    format!("{}", array.display_values()),
    "[0i16, 1i16, 2i16, 3i16, 4i16]",
)

See also: Array::display_as, DisplayArrayAs, and DisplayOptions.

pub fn display_as(&self, options: DisplayOptions) -> impl Display

Display the array as specified by the options.

See DisplayOptions for examples.

pub fn display_tree(&self) -> impl Display

Display the tree of encodings of this array as an indented lists.

While some metadata (such as length, bytes and validity-rate) are included, the logical values of the array are not displayed. To view the logical values see Array::display_as and DisplayOptions.

Examples

let array = buffer![0_i16, 1, 2, 3, 4].into_array();
let expected = "root: vortex.primitive(i16, len=5) nbytes=10 B (100.00%)
  metadata: EmptyMetadata
  buffer (align=2): 10 B (100.00%)
";
assert_eq!(format!("{}", array.display_tree()), expected);

pub fn display_table(&self) -> impl Display

Display the array as a formatted table.

For struct arrays, displays a column for each field in the struct. For regular arrays, displays a single column with values.

Examples

let s = StructArray::from_fields(&[
    ("x", buffer![1, 2].into_array()),
    ("y", buffer![3, 4].into_array()),
]).unwrap().into_array();
let expected = "
┌──────┬──────┐
│  x   │  y   │
├──────┼──────┤
│ 1i32 │ 3i32 │
├──────┼──────┤
│ 2i32 │ 4i32 │
└──────┴──────┘".trim();
assert_eq!(format!("{}", s.display_table()), expected);

pub fn as_<V: VTable>(&self) -> &V::Array

Returns the array downcast to the given A.

pub fn as_opt<V: VTable>(&self) -> Option<&V::Array>

Returns the array downcast to the given A.

pub fn is<V: VTable>(&self) -> bool

Is self an array with encoding from vtable V.

pub fn is_constant(&self) -> bool

pub fn is_constant_opts(&self, cost: Cost) -> bool

pub fn as_constant(&self) -> Option<Scalar>

pub fn nbytes(&self) -> u64

Total size of the array in bytes, including all children and buffers.

pub fn try_to_mask_fill_null_false(&self) -> VortexResult<Mask>

Converts from a possible nullable boolean array. Null values are treated as false.

pub fn to_array_iterator(&self) -> impl ArrayIterator + 'static

Create an ArrayIterator over the array.

pub fn serialize( &self, ctx: &ArrayContext, options: &SerializeOptions, ) -> VortexResult<Vec<ByteBuffer>>

Serialize the array into a sequence of byte buffers that should be written contiguously. This function returns a vec to avoid copying data buffers.

Optionally, padding can be included to guarantee buffer alignment and ensure zero-copy reads within the context of an external file or stream. In this case, the alignment of the first byte buffer should be respected when writing the buffers to the stream or file.

The format of this blob is a sequence of data buffers, possible with prefixed padding, followed by a flatbuffer containing an fba::Array message, and ending with a little-endian u32 describing the length of the flatbuffer message.

pub fn to_array_stream(&self) -> impl ArrayStream + 'static

Create an ArrayStream over the array.

pub fn as_null_typed(&self) -> NullTyped<'_>

Downcasts the array for null-specific behavior.

pub fn as_bool_typed(&self) -> BoolTyped<'_>

Downcasts the array for bool-specific behavior.

pub fn as_primitive_typed(&self) -> PrimitiveTyped<'_>

Downcasts the array for primitive-specific behavior.

pub fn as_decimal_typed(&self) -> DecimalTyped<'_>

Downcasts the array for decimal-specific behavior.

pub fn as_utf8_typed(&self) -> Utf8Typed<'_>

Downcasts the array for utf8-specific behavior.

pub fn as_binary_typed(&self) -> BinaryTyped<'_>

Downcasts the array for binary-specific behavior.

pub fn as_struct_typed(&self) -> StructTyped<'_>

Downcasts the array for struct-specific behavior.

pub fn as_list_typed(&self) -> ListTyped<'_>

Downcasts the array for list-specific behavior.

pub fn as_extension_typed(&self) -> ExtensionTyped<'_>

Downcasts the array for extension-specific behavior.

Trait Implementations

impl AsRef<dyn Array> for ListArray

fn as_ref(&self) -> &dyn Array

Converts this type into a shared reference of the (usually inferred) input type.

impl Clone for ListArray

fn clone(&self) -> ListArray

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ListArray

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

Formats the value using the given formatter.

impl Deref for ListArray

type Target = dyn Array

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl From<ListArray> for ArrayRef

fn from(value: ListArray) -> ArrayRef

Converts to this type from the input type.

impl IntoArray for ListArray

fn into_array(self) -> ArrayRef

impl ValidityHelper for ListArray

fn validity(&self) -> &Validity