Method extend_dictionary

arrow-array/src/builder/primitive_dictionary_builder.rs:383–431

Extends builder with dictionary This is the same as [`Self::extend`] but is faster as it translates the dictionary values once rather than doing a lookup for each item in the iterator when dictionary values are null (the actual mapped values) the keys are null

(
        &mut self,
        dictionary: &TypedDictionaryArray<K, PrimitiveArray<V>>,
    )

    /// when dictionary values are null (the actual mapped values) the keys are null
    ///
    pub fn extend_dictionary(
        &mut self,
        dictionary: &TypedDictionaryArray<K, PrimitiveArray<V>>,
    ) -> Result<(), ArrowError> {
        let values = dictionary.values();

        let v_len = values.len();
        let k_len = dictionary.keys().len();
        if v_len == 0 && k_len == 0 {
            return Ok(());
        }

        // All nulls
        if v_len == 0 {
            self.append_nulls(k_len);
            return Ok(());
        }

        if k_len == 0 {
            return Err(ArrowError::InvalidArgumentError(
                "Dictionary keys should not be empty when values are not empty".to_string(),
            ));
        }

        // Orphan values will be carried over to the new dictionary
        let mapped_values = values
            .iter()
            // Dictionary values can technically be null, so we need to handle that
            .map(|dict_value| {
                dict_value
                    .map(|dict_value| self.get_or_insert_key(dict_value))
                    .transpose()
            })
            .collect::<Result<Vec<_>, _>>()?;

        // Just insert the keys without additional lookups
        dictionary.keys().iter().for_each(|key| match key {
            None => self.append_null(),
            Some(original_dict_index) => {
                let index = original_dict_index.as_usize().min(v_len - 1);
                match mapped_values[index] {
                    None => self.append_null(),
                    Some(mapped_value) => self.keys_builder.append_value(mapped_value),
                }
            }
        });

        Ok(())
    }

    /// Builds the `DictionaryArray` and reset this builder.
    pub fn finish(&mut self) -> DictionaryArray<K> {