Struct arrow::array::StringDictionaryBuilder
source · [−]pub struct StringDictionaryBuilder<K> where
K: ArrowDictionaryKeyType, { /* private fields */ }
Expand description
Array builder for DictionaryArray
that stores Strings. For example to map a set of byte indices
to String values. Note that the use of a HashMap
here will not scale to very large
arrays or result in an ordered dictionary.
use arrow::{
array::{
Int8Array, StringArray,
PrimitiveBuilder, StringBuilder, StringDictionaryBuilder,
},
datatypes::Int8Type,
};
// Create a dictionary array indexed by bytes whose values are Strings.
// It can thus hold up to 256 distinct string values.
let key_builder = PrimitiveBuilder::<Int8Type>::new(100);
let value_builder = StringBuilder::new(100);
let mut builder = StringDictionaryBuilder::new(key_builder, value_builder);
// The builder builds the dictionary value by value
builder.append("abc").unwrap();
builder.append_null().unwrap();
builder.append("def").unwrap();
builder.append("def").unwrap();
builder.append("abc").unwrap();
let array = builder.finish();
assert_eq!(
array.keys(),
&Int8Array::from(vec![Some(0), None, Some(1), Some(1), Some(0)])
);
// Values are polymorphic and so require a downcast.
let av = array.values();
let ava: &StringArray = av.as_any().downcast_ref::<StringArray>().unwrap();
assert_eq!(ava.value(0), "abc");
assert_eq!(ava.value(1), "def");
Implementations
sourceimpl<K> StringDictionaryBuilder<K> where
K: ArrowDictionaryKeyType,
impl<K> StringDictionaryBuilder<K> where
K: ArrowDictionaryKeyType,
sourcepub fn new(
keys_builder: PrimitiveBuilder<K>,
values_builder: StringBuilder
) -> Self
pub fn new(
keys_builder: PrimitiveBuilder<K>,
values_builder: StringBuilder
) -> Self
Creates a new StringDictionaryBuilder
from a keys builder and a value builder.
sourcepub fn new_with_dictionary(
keys_builder: PrimitiveBuilder<K>,
dictionary_values: &StringArray
) -> Result<Self>
pub fn new_with_dictionary(
keys_builder: PrimitiveBuilder<K>,
dictionary_values: &StringArray
) -> Result<Self>
Creates a new StringDictionaryBuilder
from a keys builder and a dictionary
which is initialized with the given values.
The indices of those dictionary values are used as keys.
Example
use arrow::datatypes::Int16Type;
use arrow::array::{StringArray, StringDictionaryBuilder, PrimitiveBuilder, Int16Array};
use std::convert::TryFrom;
let dictionary_values = StringArray::from(vec![None, Some("abc"), Some("def")]);
let mut builder = StringDictionaryBuilder::new_with_dictionary(PrimitiveBuilder::<Int16Type>::new(3), &dictionary_values).unwrap();
builder.append("def").unwrap();
builder.append_null().unwrap();
builder.append("abc").unwrap();
let dictionary_array = builder.finish();
let keys = dictionary_array.keys();
assert_eq!(keys, &Int16Array::from(vec![Some(2), None, Some(1)]));
sourceimpl<K> StringDictionaryBuilder<K> where
K: ArrowDictionaryKeyType,
impl<K> StringDictionaryBuilder<K> where
K: ArrowDictionaryKeyType,
sourcepub fn append(&mut self, value: impl AsRef<str>) -> Result<K::Native>
pub fn append(&mut self, value: impl AsRef<str>) -> 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<()>
sourcepub fn finish(&mut self) -> DictionaryArray<K>
pub fn finish(&mut self) -> DictionaryArray<K>
Builds the DictionaryArray
and reset this builder.
Trait Implementations
sourceimpl<K> ArrayBuilder for StringDictionaryBuilder<K> where
K: ArrowDictionaryKeyType,
impl<K> ArrayBuilder for StringDictionaryBuilder<K> where
K: ArrowDictionaryKeyType,
sourcefn as_any_mut(&mut self) -> &mut dyn Any
fn as_any_mut(&mut self) -> &mut dyn Any
Returns the builder as an mutable Any
reference.
sourcefn into_box_any(self: Box<Self>) -> Box<dyn Any>
fn into_box_any(self: Box<Self>) -> Box<dyn Any>
Returns the boxed builder as a box of Any
.
Auto Trait Implementations
impl<K> RefUnwindSafe for StringDictionaryBuilder<K> where
<K as ArrowPrimitiveType>::Native: RefUnwindSafe,
impl<K> Send for StringDictionaryBuilder<K>
impl<K> Sync for StringDictionaryBuilder<K>
impl<K> Unpin for StringDictionaryBuilder<K> where
<K as ArrowPrimitiveType>::Native: Unpin,
impl<K> UnwindSafe for StringDictionaryBuilder<K> where
<K as ArrowPrimitiveType>::Native: UnwindSafe,
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more