Struct arrow::array::PrimitiveDictionaryBuilder [−][src]
pub struct PrimitiveDictionaryBuilder<K, V> where
K: ArrowPrimitiveType,
V: ArrowPrimitiveType, { /* fields omitted */ }
Expand description
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,
impl<K, V> PrimitiveDictionaryBuilder<K, V> where
K: ArrowPrimitiveType,
V: ArrowPrimitiveType,
Creates a new PrimitiveDictionaryBuilder
from a keys builder and a value builder.
impl<K, V> PrimitiveDictionaryBuilder<K, V> where
K: ArrowPrimitiveType,
V: ArrowPrimitiveType,
impl<K, V> PrimitiveDictionaryBuilder<K, V> where
K: ArrowPrimitiveType,
V: ArrowPrimitiveType,
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.
Builds the DictionaryArray
and reset this builder.
Trait Implementations
impl<K, V> ArrayBuilder for PrimitiveDictionaryBuilder<K, V> where
K: ArrowPrimitiveType,
V: ArrowPrimitiveType,
impl<K, V> ArrayBuilder for PrimitiveDictionaryBuilder<K, V> where
K: ArrowPrimitiveType,
V: ArrowPrimitiveType,
Returns the builder as an mutable Any
reference.
Returns the boxed builder as a box of Any
.