Struct arrow::array::DictionaryArray

pub struct DictionaryArray<K: ArrowPrimitiveType> { /* fields omitted */ }

A dictionary array where each element is a single value indexed by an integer key. This is mostly used to represent strings or a limited set of primitive types as integers, for example when doing NLP analysis or representing chromosomes by name.

Example with nullable data:

use arrow::array::{DictionaryArray, Int8Array};
use arrow::datatypes::Int8Type;
let test = vec!["a", "a", "b", "c"];
let array : DictionaryArray<Int8Type> = test.iter().map(|&x| if x == "b" {None} else {Some(x)}).collect();
assert_eq!(array.keys(), &Int8Array::from(vec![Some(0), Some(0), None, Some(1)]));

Example without nullable data:

use arrow::array::{DictionaryArray, Int8Array};
use arrow::datatypes::Int8Type;
let test = vec!["a", "a", "b", "c"];
let array : DictionaryArray<Int8Type> = test.into_iter().collect();
assert_eq!(array.keys(), &Int8Array::from(vec![0, 0, 1, 2]));

Implementations

impl<'a, K: ArrowPrimitiveType> DictionaryArray<K>

pub fn keys(&self) -> &PrimitiveArray<K>

Return an iterator to the keys of this dictionary.

pub fn keys_array(&self) -> PrimitiveArray<K>

Returns an array view of the keys of this dictionary

pub fn lookup_key(&self, value: &str) -> Option<K::Native>

Returns the lookup key by doing reverse dictionary lookup

pub fn values(&self) -> ArrayRef

Returns an ArrayRef to the dictionary values.

pub fn value_type(&self) -> DataType

Returns a clone of the value type of this list.

pub fn len(&self) -> usize

The length of the dictionary is the length of the keys array.

pub fn is_empty(&self) -> bool

Whether this dictionary is empty

pub fn is_ordered(&self) -> bool

Trait Implementations

impl<T: ArrowPrimitiveType> Array for DictionaryArray<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 get_buffer_memory_size(&self) -> usize

Returns the total number of bytes of memory occupied by the buffers owned by this array.

fn get_array_memory_size(&self) -> usize

Returns the total number of bytes of memory occupied physically by 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 to_raw(&self) -> Result<(*const FFI_ArrowArray, *const FFI_ArrowSchema)>

returns two pointers that represent this array in the C Data Interface (FFI)

impl<T: ArrowPrimitiveType> Debug for DictionaryArray<T>

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

Formats the value using the given formatter.

impl<T: ArrowPrimitiveType> From<ArrayData> for DictionaryArray<T>

Constructs a DictionaryArray from an array data reference.

fn from(data: ArrayData) -> Self

Performs the conversion.

impl<'a, T: ArrowPrimitiveType + ArrowDictionaryKeyType> FromIterator<&'a str> for DictionaryArray<T>

Constructs a DictionaryArray from an iterator of strings.

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

Creates a value from an iterator.

impl<'a, T: ArrowPrimitiveType + ArrowDictionaryKeyType> FromIterator<Option<&'a str>> for DictionaryArray<T>

Constructs a DictionaryArray from an iterator of optional strings.

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

Creates a value from an iterator.

impl<T: ArrowPrimitiveType> JsonEqual for DictionaryArray<T>

fn equals_json(&self, json: &[&Value]) -> bool

Checks whether arrow array equals to json array.

fn equals_json_values(&self, json: &[Value]) -> bool

Checks whether arrow array equals to json array.

impl<T: ArrowPrimitiveType> PartialEq<Value> for DictionaryArray<T>

fn eq(&self, json: &Value) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use]

fn ne(&self, other: &Rhs) -> bool

This method tests for !=.