tustvold commented on code in PR #5149:
URL: https://github.com/apache/arrow-rs/pull/5149#discussion_r1409308240
##########
arrow-schema/src/fields.rs:
##########
@@ -99,6 +100,90 @@ impl Fields {
.all(|(a, b)| Arc::ptr_eq(a, b) || a.contains(b))
}
+ /// Performs a depth-first scan of [`Fields`] filtering the [`FieldRef`]
with no children
+ ///
+ /// Returns a new [`Fields`] comprising the [`FieldRef`] for which
`filter` returned `true`
+ ///
+ /// ```
+ /// # use arrow_schema::{DataType, Field, Fields};
+ /// let fields = Fields::from(vec![
+ /// Field::new("a", DataType::Int32, true),
+ /// Field::new("b", DataType::Struct(Fields::from(vec![
+ /// Field::new("c", DataType::Float32, false),
+ /// Field::new("d", DataType::Float64, false),
+ /// ])), false)
+ /// ]);
+ /// let filtered = fields.filter_leaves(|idx, _| idx == 0 || idx == 2);
+ /// let expected = Fields::from(vec![
+ /// Field::new("a", DataType::Int32, true),
+ /// Field::new("b", DataType::Struct(Fields::from(vec![
+ /// Field::new("d", DataType::Float64, false),
+ /// ])), false)
+ /// ]);
+ /// assert_eq!(filtered, expected);
+ /// ```
+ pub fn filter_leaves<F: FnMut(usize, &FieldRef) -> bool>(&self, mut
filter: F) -> Self {
Review Comment:
Originally I had two methods, one which was called for all Fields, however,
it wasn't clear to me how such an API could be used - as it would lack any
context as to where in the schema a given field appeared. I therefore just
stuck with filter_leaves which has immediate concrete utility for #5135
FYI @Jefffrey
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