alamb commented on a change in pull request #1296:
URL: https://github.com/apache/arrow-rs/pull/1296#discussion_r804061136
##########
File path: arrow/src/array/iterator.rs
##########
@@ -403,6 +403,109 @@ impl<'a, S: OffsetSizeTrait> std::iter::ExactSizeIterator
{
}
+/// an iterator that returns Some(T) or None, that can be used on any
DictionaryArray
+// Note: This implementation is based on std's [Vec]s' [IntoIter].
+#[derive(Debug)]
+pub struct DictionaryIter<'a, K: ArrowPrimitiveType, T: ArrowPrimitiveType> {
+ array: &'a DictionaryArray<K>,
+ values: &'a PrimitiveArray<T>,
+ current: usize,
+ current_end: usize,
+}
Review comment:
🤔 as you note, the way this is implemented, it will only work for
DictionaryArrays whose values are `PrimitiveArray<>` such as `Int64Array`
If we take this approach, we'll probably end up with different iterator
types for different value types like
```rust
pub struct DictionaryIterPrimitive<'a, K: ArrowPrimitiveType, T:
ArrowPrimitiveType> {
...
}
impl<'a, K: ArrowPrimitiveType, T: ArrowPrimitiveType> std::iter::Iterator
for DictionaryIter<'a, K, T>
{
type Item = Option<T::Native>;
...
}
```
```rust
pub struct DictionaryIterBool<'a, K: ArrowPrimitiveType> {
...
}
impl <'a, K: ArrowPrimitiveType> std::iter::Iterator for
DictionaryIterBool<'a, K>
{
type Item = Option<bool>;
...
}
...
```
And then functions like the following
```rust
impl DictionaryArray {
pub fn iter_primitive<T>::(&self) -> DictionaryIterPrimitive
...
}
pub fn iter_bool<T>::(&self) -> DictionaryIterBool
...
}
}
```
Which would effectively require the user to know what type of values their
dictionary held
🤔
##########
File path: arrow/src/array/iterator.rs
##########
@@ -403,6 +403,109 @@ impl<'a, S: OffsetSizeTrait> std::iter::ExactSizeIterator
{
}
+/// an iterator that returns Some(T) or None, that can be used on any
DictionaryArray
+// Note: This implementation is based on std's [Vec]s' [IntoIter].
+#[derive(Debug)]
+pub struct DictionaryIter<'a, K: ArrowPrimitiveType, T: ArrowPrimitiveType> {
+ array: &'a DictionaryArray<K>,
+ values: &'a PrimitiveArray<T>,
+ current: usize,
+ current_end: usize,
+}
Review comment:
Thinking some more we could potentially avoid parameterizing on the key
type by always upcasting the indexes to `usize` (which has to happen anyways)
before creating the iterator
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