Struct arrow_array::builder::PrimitiveDictionaryBuilder

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

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:

let mut builder = PrimitiveDictionaryBuilder::<UInt8Type, UInt32Type>::new();
 builder.append(12345678).unwrap();
 builder.append_null();
 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() -> Self

Creates a new PrimitiveDictionaryBuilder.

pub fn with_capacity(keys_capacity: usize, values_capacity: usize) -> Self

Creates a new PrimitiveDictionaryBuilder with the provided capacities

keys_capacity: the number of keys, i.e. length of array to build values_capacity: the number of distinct dictionary values, i.e. size of dictionary

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

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

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)

Appends a null slot into the builder

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

Builds the DictionaryArray and reset this builder.

pub fn finish_cloned(&self) -> DictionaryArray<K>

Builds the DictionaryArray without resetting the 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.

fn finish_cloned(&self) -> ArrayRef

Builds the array without resetting the builder.

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

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

Formats the value using the given formatter.

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

fn default() -> Self

Returns the “default value” for a type.