Trait deltalake::arrow::array::array::AnyDictionaryArray

source ·

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

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"]);