junjunjd commented on code in PR #7901:
URL: https://github.com/apache/arrow-datafusion/pull/7901#discussion_r1378379142
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datafusion/common/src/scalar.rs:
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@@ -512,19 +516,19 @@ impl std::hash::Hash for ScalarValue {
pub fn get_dict_value<K: ArrowDictionaryKeyType>(
array: &dyn Array,
index: usize,
-) -> (&ArrayRef, Option<usize>) {
- let dict_array = as_dictionary_array::<K>(array).unwrap();
- (dict_array.values(), dict_array.key(index))
+) -> Result<(&ArrayRef, Option<usize>)> {
+ let dict_array = as_dictionary_array::<K>(array)?;
Review Comment:
This is a public function and `as_dictionary_array` can fail depending on
what `array` value the user passes to the function. The
[`downcast_value`](https://github.com/apache/arrow-datafusion/blob/main/datafusion/common/src/lib.rs#L73)
macro called by `as_dictionary_array` returns an internal error if the cast is
impossible.
I think returning a `Result` here makes sense because this error is
reachable and recoverable (user can handle the error and only passes in arrays
that can be downcast to `DictionaryArray`). If panic is preferred here, we can
establish an invariant that the `array` value passed to the function should be
able to downcast to `DictionaryArray`.
`get_dict_value` is only called in `try_from_array`, which already returns a
`Result`.
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