Struct arrow::array::PrimitiveDictionaryBuilder

pub struct PrimitiveDictionaryBuilder<K, V> where
    K: ArrowPrimitiveType,
    V: ArrowPrimitiveType,  { /* fields omitted */ }

Array builder for DictionaryArray. For example to map a set of byte indices to f32 values. Note that the use of a HashMap here will not scale to very large arrays or result in an ordered dictionary.

Example:

 use arrow::array::{
     Array, PrimitiveBuilder, PrimitiveDictionaryBuilder,
     UInt8Array, UInt32Array,
   };
 use arrow::datatypes::{UInt8Type, UInt32Type};

 let key_builder = PrimitiveBuilder::<UInt8Type>::new(3);
 let value_builder = PrimitiveBuilder::<UInt32Type>::new(2);
 let mut builder = PrimitiveDictionaryBuilder::new(key_builder, value_builder);
 builder.append(12345678).unwrap();
 builder.append_null().unwrap();
 builder.append(22345678).unwrap();
 let array = builder.finish();

 assert_eq!(
     array.keys(),
     &UInt8Array::from(vec![Some(0), None, Some(1)])
 );

 // Values are polymorphic and so require a downcast.
 let av = array.values();
 let ava: &UInt32Array = av.as_any().downcast_ref::<UInt32Array>().unwrap();
 let avs: &[u32] = ava.values();

 assert!(!array.is_null(0));
 assert!(array.is_null(1));
 assert!(!array.is_null(2));

 assert_eq!(avs, &[12345678, 22345678]);

Implementations

impl<K, V> PrimitiveDictionaryBuilder<K, V> where
    K: ArrowPrimitiveType,
    V: ArrowPrimitiveType, 

pub fn new(
    keys_builder: PrimitiveBuilder<K>,
    values_builder: PrimitiveBuilder<V>
) -> Self

Creates a new PrimitiveDictionaryBuilder from a keys builder and a value builder.

impl<K, V> PrimitiveDictionaryBuilder<K, V> where
    K: ArrowPrimitiveType,
    V: ArrowPrimitiveType, 

pub fn append(&mut self, value: V::Native) -> Result<K::Native>

Append a primitive value to the array. Return an existing index if already present in the values array or a new index if the value is appended to the values array.

pub fn append_null(&mut self) -> Result<()>

pub fn finish(&mut self) -> DictionaryArray<K>

Builds the DictionaryArray and reset this builder.

Trait Implementations

impl<K, V> ArrayBuilder for PrimitiveDictionaryBuilder<K, V> where
    K: ArrowPrimitiveType,
    V: ArrowPrimitiveType, 

fn as_any(&self) -> &dyn Any

Returns the builder as an non-mutable Any reference.

fn as_any_mut(&mut self) -> &mut dyn Any

Returns the builder as an mutable Any reference.

fn into_box_any(self: Box<Self>) -> Box<dyn Any>

Returns the boxed builder as a box of Any.

fn len(&self) -> usize

Returns the number of array slots in the builder

fn is_empty(&self) -> bool

Returns whether the number of array slots is zero

fn finish(&mut self) -> ArrayRef

Builds the array and reset this builder.

impl<K: Debug, V: Debug> Debug for PrimitiveDictionaryBuilder<K, V> where
    K: ArrowPrimitiveType,
    V: ArrowPrimitiveType,
    K::Native: Debug, 

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

Formats the value using the given formatter.