Andy Thomason created ARROW-7700:
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Summary: [Rust] All array types should have iterators and
FromIterator support.
Key: ARROW-7700
URL: https://issues.apache.org/jira/browse/ARROW-7700
Project: Apache Arrow
Issue Type: Bug
Components: Rust
Reporter: Andy Thomason
Array types should have an Iterable trait that generates plain or nullable
iterators.
{code}
pub trait Iterable<'a>
where Self::IterType: std::iter::Iterator
{
type IterType;
fn iter(&'a self) -> Self::IterType;
fn iter_nulls(&'a self) -> NullableIterator<Self::IterType>;
}
{code}
IterType depends on the array type from standard slice iterators for primitive
types, string iterators for UTF8 types and composite iterators (generating
other iterators) for list, struct and dictionary types.
The NullableIterator type should bundle a null bitmap pointer with another
iterator type to form a composite iterator that returns an option:
{code}
/// Convert any iterator to a nullable iterator by using the null bitmap.
#[derive(Debug, PartialEq, Clone)]
pub struct NullableIterator<T: Iterator> {
iter: T,
i: usize,
null_bitmap: *const u8,
}
impl<T: Iterator> NullableIterator<T> {
fn from(iter: T, null_bitmap: &Option<Bitmap>, offset: usize) -> Self;
}
{code}
For more details, some exploratory work has been done here:
https://github.com/andy-thomason/arrow/blob/ARROW-iterators/rust/arrow/src/array/array.rs#L1711
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