arrow_array::array

Trait AnyDictionaryArray

Source
pub trait AnyDictionaryArray: Array {
    // Required methods
    fn keys(&self) -> &dyn Array;
    fn values(&self) -> &ArrayRef;
    fn normalized_keys(&self) -> Vec<usize>;
    fn with_values(&self, values: ArrayRef) -> ArrayRef;
}
Expand description

A DictionaryArray with the key type erased

This can be used to efficiently implement kernels for all possible dictionary keys without needing to create specialized implementations for each key type

For example


fn to_string(a: &dyn Array) -> Result<ArrayRef, ArrowError> {
    if let Some(d) = a.as_any_dictionary_opt() {
        // Recursively handle dictionary input
        let r = to_string(d.values().as_ref())?;
        return Ok(d.with_values(r));
    }
    downcast_primitive_array! {
        a => Ok(Arc::new(a.iter().map(|x| x.map(|x| x.to_string())).collect::<StringArray>())),
        d => Err(ArrowError::InvalidArgumentError(format!("{d:?} not supported")))
    }
}

let result = to_string(&Int32Array::from(vec![1, 2, 3])).unwrap();
let actual = result.as_string::<i32>().iter().map(Option::unwrap).collect::<Vec<_>>();
assert_eq!(actual, &["1", "2", "3"]);

let mut dict = PrimitiveDictionaryBuilder::<Int32Type, UInt16Type>::new();
dict.extend([Some(1), Some(1), Some(2), Some(3), Some(2)]);
let dict = dict.finish();

let r = to_string(&dict).unwrap();
let r = r.as_dictionary::<Int32Type>().downcast_dict::<StringArray>().unwrap();
assert_eq!(r.keys(), dict.keys()); // Keys are the same

let actual = r.into_iter().map(Option::unwrap).collect::<Vec<_>>();
assert_eq!(actual, &["1", "1", "2", "3", "2"]);

See AsArray::as_any_dictionary_opt and AsArray::as_any_dictionary

Required Methods§

Source

fn keys(&self) -> &dyn Array

Returns the primitive keys of this dictionary as an Array

Source

fn values(&self) -> &ArrayRef

Returns the values of this dictionary

Source

fn normalized_keys(&self) -> Vec<usize>

Returns the keys of this dictionary as usize

The values for nulls will be arbitrary, but are guaranteed to be in the range 0..self.values.len()

§Panic

Panics if values.len() == 0

Source

fn with_values(&self, values: ArrayRef) -> ArrayRef

Create a new DictionaryArray replacing values with the new values

See DictionaryArray::with_values

Implementors§