Struct arrow_array::array::RunArray

pub struct RunArray<R: RunEndIndexType> { /* private fields */ }

A run-end encoding (REE) is a variation of run-length encoding (RLE).

This encoding is good for representing data containing same values repeated consecutively.

RunArray contains run_ends array and values array of same length. The run_ends array stores the indexes at which the run ends. The values array stores the value of each run. Below example illustrates how a logical array is represented in RunArray

┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─┐
  ┌─────────────────┐  ┌─────────┐       ┌─────────────────┐
│ │        A        │  │    2    │ │     │        A        │     
  ├─────────────────┤  ├─────────┤       ├─────────────────┤
│ │        D        │  │    3    │ │     │        A        │    run length of 'A' = runs_ends[0] - 0 = 2
  ├─────────────────┤  ├─────────┤       ├─────────────────┤
│ │        B        │  │    6    │ │     │        D        │    run length of 'D' = run_ends[1] - run_ends[0] = 1
  └─────────────────┘  └─────────┘       ├─────────────────┤
│        values          run_ends  │     │        B        │     
                                         ├─────────────────┤
└ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─┘     │        B        │     
                                         ├─────────────────┤
               RunArray                  │        B        │    run length of 'B' = run_ends[2] - run_ends[1] = 3
              length = 3                 └─────────────────┘
  
                                            Logical array
                                               Contents

Implementations

impl<R: RunEndIndexType> RunArray<R>

pub fn try_new(
    run_ends: &PrimitiveArray<R>,
    values: &dyn Array
) -> Result<Self, ArrowError>

Attempts to create RunArray using given run_ends (index where a run ends) and the values (value of the run). Returns an error if the given data is not compatible with RunEndEncoded specification.

pub fn run_ends(&self) -> &PrimitiveArray<R>

Returns a reference to run_ends array

Note: any slicing of this array is not applied to the returned array and must be handled separately

pub fn values(&self) -> &ArrayRef

Returns a reference to values array

Trait Implementations

impl<T: RunEndIndexType> Array for RunArray<T>

fn as_any(&self) -> &dyn Any

Returns the array as Any so that it can be downcasted to a specific implementation.

fn data(&self) -> &ArrayData

Returns a reference to the underlying data of this array.

fn into_data(self) -> ArrayData

Returns the underlying data of this array.

fn data_ref(&self) -> &ArrayData

Returns a reference-counted pointer to the underlying data of this array.

fn data_type(&self) -> &DataType

Returns a reference to the DataType of this array.

fn slice(&self, offset: usize, length: usize) -> ArrayRef

Returns a zero-copy slice of this array with the indicated offset and length.

fn len(&self) -> usize

Returns the length (i.e., number of elements) of this array.

fn is_empty(&self) -> bool

Returns whether this array is empty.

fn offset(&self) -> usize

Returns the offset into the underlying data used by this array(-slice). Note that the underlying data can be shared by many arrays. This defaults to 0.

fn is_null(&self, index: usize) -> bool

Returns whether the element at index is null. When using this function on a slice, the index is relative to the slice.

fn is_valid(&self, index: usize) -> bool

Returns whether the element at index is not null. When using this function on a slice, the index is relative to the slice.

fn null_count(&self) -> usize

Returns the total number of null values in this array.

fn get_buffer_memory_size(&self) -> usize

Returns the total number of bytes of memory pointed to by this array. The buffers store bytes in the Arrow memory format, and include the data as well as the validity map.

fn get_array_memory_size(&self) -> usize

Returns the total number of bytes of memory occupied physically by this array. This value will always be greater than returned by get_buffer_memory_size() and includes the overhead of the data structures that contain the pointers to the various buffers.

impl<R: RunEndIndexType> Debug for RunArray<R>

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

Formats the value using the given formatter.

impl<R: RunEndIndexType> From<ArrayData> for RunArray<R>

fn from(data: ArrayData) -> Self

Converts to this type from the input type.

impl<R: RunEndIndexType> From<RunArray<R>> for ArrayData

fn from(array: RunArray<R>) -> Self

Converts to this type from the input type.

impl<'a, T: RunEndIndexType> FromIterator<&'a str> for RunArray<T>

Constructs a RunArray from an iterator of strings.

Example:

use arrow_array::{RunArray, PrimitiveArray, StringArray, types::Int16Type};

let test = vec!["a", "a", "b", "c"];
let array: RunArray<Int16Type> = test.into_iter().collect();
assert_eq!(
    "RunArray {run_ends: PrimitiveArray<Int16>\n[\n  2,\n  3,\n  4,\n], values: StringArray\n[\n  \"a\",\n  \"b\",\n  \"c\",\n]}\n",
    format!("{:?}", array)
);

fn from_iter<I: IntoIterator<Item = &'a str>>(iter: I) -> Self

Creates a value from an iterator.

impl<'a, T: RunEndIndexType> FromIterator<Option<&'a str>> for RunArray<T>

Constructs a RunArray from an iterator of optional strings.

Example:

use arrow_array::{RunArray, PrimitiveArray, StringArray, types::Int16Type};

let test = vec!["a", "a", "b", "c", "c"];
let array: RunArray<Int16Type> = test
    .iter()
    .map(|&x| if x == "b" { None } else { Some(x) })
    .collect();
assert_eq!(
    "RunArray {run_ends: PrimitiveArray<Int16>\n[\n  2,\n  3,\n  5,\n], values: StringArray\n[\n  \"a\",\n  null,\n  \"c\",\n]}\n",
    format!("{:?}", array)
);

fn from_iter<I: IntoIterator<Item = Option<&'a str>>>(iter: I) -> Self

Creates a value from an iterator.