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https://issues.apache.org/jira/browse/ARROW-8383?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17185450#comment-17185450
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Jörn Horstmann commented on ARROW-8383:
---------------------------------------
So I found out that the alternative/workaround
{code:java}
let keys : Int16Array = dictionary_array.data().into()
{code}
Does not really work that well because the {{data_type()}} function of the
resulting primitive array would still return {{DataType::Dictionary}} which can
lead to problems later on.
I propose adding a function
{code}
pub fn keys_array(&self) -> PrimitiveArray<K>
{code}
Which constructs a primitive array around a ArrayData object containing the
data type of the key.
> [RUST] Easier random access to DictionaryArray keys and values
> --------------------------------------------------------------
>
> Key: ARROW-8383
> URL: https://issues.apache.org/jira/browse/ARROW-8383
> Project: Apache Arrow
> Issue Type: Improvement
> Components: Rust
> Reporter: Jörn Horstmann
> Priority: Minor
>
> Currently it's not that clear how to acces DictionaryArray keys and values
> using random indices.
> The `DictionaryArray::keys` method exposes an Iterator with an `nth` method,
> but this requires a mut reference and feels a little bit out of place
> compared to other methods of accessing arrow data.
> Another alternative seems to be to use the `From<ArrayDataRef> for
> PrimitiveArray<T>` conversion like so `let keys : Int16Array =
> dictionary_array.data().into()`. This seems to work fine but is not easily
> discoverable and also needs to be done outside of any loops for performance
> reasons.
> I'd like methods on `DictionaryArray` to directly get the key at some index
> ```
> pub fn key(&self, i: usize) -> &K
> ```
> Ideally I'd also like an easier way to directly access values at some index,
> at least when those are primitive or string types.
> ```
> pub fn value(&self, i: usize) -> &T
> ```
> I'm not sure how or if that would be possible to implement with rust generics.
>
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