scovich commented on code in PR #8625:
URL: https://github.com/apache/arrow-rs/pull/8625#discussion_r2432819812
##########
parquet-variant-compute/src/variant_array.rs:
##########
@@ -439,6 +440,22 @@ impl From<VariantArray> for ArrayRef {
}
}
+impl<'m, 'v> FromIterator<Option<Variant<'m, 'v>>> for VariantArray {
+ fn from_iter<T: IntoIterator<Item = Option<Variant<'m, 'v>>>>(iter: T) ->
Self {
+ let mut b = VariantArrayBuilder::new(0);
+ b.extend(iter);
+ b.build()
+ }
+}
+
+impl<'m, 'v> FromIterator<Variant<'m, 'v>> for VariantArray {
+ fn from_iter<T: IntoIterator<Item = Variant<'m, 'v>>>(iter: T) -> Self {
+ let mut b = VariantArrayBuilder::new(0);
+ b.extend(iter);
+ b.build()
+ }
+}
+
Review Comment:
Most std lib code I've seen relies on the iterator's lower bound
[hint](https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.size_hint),
with a fallback path if that turned out to be too low.
There's also the
[ExactSizeIterator](https://doc.rust-lang.org/std/iter/trait.ExactSizeIterator.html)
trait, but given how rust treats potentially overlapping generic definitions
as conflicts, I don't know how to provide implementations for both Iterator and
ExactSizeIterator?
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