Struct arrow::array::StringDictionaryBuilder [−][src]
pub struct StringDictionaryBuilder<K> where
K: ArrowDictionaryKeyType, { /* fields omitted */ }
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
impl<K> StringDictionaryBuilder<K> where
K: ArrowDictionaryKeyType,
[src]
impl<K> StringDictionaryBuilder<K> where
K: ArrowDictionaryKeyType,
[src]pub fn new(
keys_builder: PrimitiveBuilder<K>,
values_builder: StringBuilder
) -> Self
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pub fn new(
keys_builder: PrimitiveBuilder<K>,
values_builder: StringBuilder
) -> Self
[src]Creates a new StringDictionaryBuilder
from a keys builder and a value builder.
pub fn new_with_dictionary(
keys_builder: PrimitiveBuilder<K>,
dictionary_values: &StringArray
) -> Result<Self>
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pub fn new_with_dictionary(
keys_builder: PrimitiveBuilder<K>,
dictionary_values: &StringArray
) -> Result<Self>
[src]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)]));
impl<K> StringDictionaryBuilder<K> where
K: ArrowDictionaryKeyType,
[src]
impl<K> StringDictionaryBuilder<K> where
K: ArrowDictionaryKeyType,
[src]pub fn append(&mut self, value: impl AsRef<str>) -> Result<K::Native>
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pub fn append(&mut self, value: impl AsRef<str>) -> Result<K::Native>
[src]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<()>
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pub fn finish(&mut self) -> DictionaryArray<K>
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pub fn finish(&mut self) -> DictionaryArray<K>
[src]Builds the DictionaryArray
and reset this builder.
Trait Implementations
impl<K> ArrayBuilder for StringDictionaryBuilder<K> where
K: ArrowDictionaryKeyType,
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impl<K> ArrayBuilder for StringDictionaryBuilder<K> where
K: ArrowDictionaryKeyType,
[src]fn as_any_mut(&mut self) -> &mut dyn Any
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fn as_any_mut(&mut self) -> &mut dyn Any
[src]Returns the builder as an mutable Any
reference.
fn into_box_any(self: Box<Self>) -> Box<dyn Any>
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fn into_box_any(self: Box<Self>) -> Box<dyn Any>
[src]Returns the boxed builder as a box of Any
.
Auto Trait Implementations
impl<K> RefUnwindSafe for StringDictionaryBuilder<K> where
<K as ArrowPrimitiveType>::Native: RefUnwindSafe,
<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,
<K as ArrowPrimitiveType>::Native: Unpin,
impl<K> UnwindSafe for StringDictionaryBuilder<K> where
<K as ArrowPrimitiveType>::Native: UnwindSafe,
<K as ArrowPrimitiveType>::Native: UnwindSafe,
Blanket Implementations
impl<T> BorrowMut<T> for T where
T: ?Sized,
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impl<T> BorrowMut<T> for T where
T: ?Sized,
[src]pub fn borrow_mut(&mut self) -> &mut T
[src]
pub fn borrow_mut(&mut self) -> &mut T
[src]Mutably borrows from an owned value. Read more
impl<V, T> VZip<V> for T where
V: MultiLane<T>,
impl<V, T> VZip<V> for T where
V: MultiLane<T>,