Struct arrow::array::DictionaryArray[][src]

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

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

Return an array view of the keys of this dictionary as a PrimitiveArray.

Returns the lookup key by doing reverse dictionary lookup

Returns a reference to the dictionary values array

Returns a clone of the value type of this list.

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

Whether this dictionary is empty

Trait Implementations

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

Returns a reference to the underlying data of this array.

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

Returns a reference to the DataType of this array. Read more

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

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

Returns whether this array is empty. Read more

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. Read more

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

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

Returns the total number of null values in this array. Read more

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. Read more

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. Read more

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

Formats the value using the given formatter. Read more

Constructs a DictionaryArray from an array data reference.

Performs the conversion.

Constructs a DictionaryArray from an iterator of strings.

Example:

use arrow::array::{DictionaryArray, PrimitiveArray, StringArray};
use arrow::datatypes::Int8Type;

let test = vec!["a", "a", "b", "c"];
let array: DictionaryArray<Int8Type> = test.into_iter().collect();
assert_eq!(
    "DictionaryArray {keys: PrimitiveArray<Int8>\n[\n  0,\n  0,\n  1,\n  2,\n] values: StringArray\n[\n  \"a\",\n  \"b\",\n  \"c\",\n]}\n",
    format!("{:?}", array)
);

Creates a value from an iterator. Read more

Constructs a DictionaryArray from an iterator of optional strings.

Example:

use arrow::array::{DictionaryArray, PrimitiveArray, StringArray};
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!(
    "DictionaryArray {keys: PrimitiveArray<Int8>\n[\n  0,\n  0,\n  null,\n  1,\n] values: StringArray\n[\n  \"a\",\n  \"c\",\n]}\n",
    format!("{:?}", array)
);

Creates a value from an iterator. Read more

Checks whether arrow array equals to json array.

Checks whether arrow array equals to json array.

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

This method tests for !=.

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

This method tests for !=.

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Performs the conversion.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.