tustvold commented on code in PR #3954:
URL: https://github.com/apache/arrow-rs/pull/3954#discussion_r1148590506
##########
arrow-array/src/builder/generic_list_builder.rs:
##########
@@ -125,11 +125,97 @@ where
/// Panics if the length of [`Self::values`] exceeds `OffsetSize::MAX`
#[inline]
pub fn append(&mut self, is_valid: bool) {
- self.offsets_builder
-
.append(OffsetSize::from_usize(self.values_builder.len()).unwrap());
+ self.offsets_builder.append(self.next_offset());
self.null_buffer_builder.append(is_valid);
}
+ /// Returns the next offset
+ ///
+ /// # Panics
+ ///
+ /// Panics if the length of [`Self::values`] exceeds `OffsetSize::MAX`
+ #[inline]
+ fn next_offset(&self) -> OffsetSize {
+ OffsetSize::from_usize(self.values_builder.len()).unwrap()
+ }
+
+ /// Append a value to this [`GenericListBuilder`]
+ ///
+ /// ```
+ /// # use arrow_array::builder::{Int32Builder, ListBuilder};
+ /// # use arrow_array::cast::AsArray;
+ /// # use arrow_array::{Array, Int32Array};
+ /// # use arrow_array::types::Int32Type;
+ /// let mut builder = ListBuilder::new(Int32Builder::new());
+ ///
+ /// builder.append_value([Some(1), Some(2), Some(3)]);
+ /// builder.append_value([]);
+ /// builder.append_value([None]);
+ ///
+ /// let array = builder.finish();
+ /// assert_eq!(array.len(), 3);
+ ///
+ /// assert_eq!(array.value_offsets(), &[0, 3, 3, 4]);
+ /// let values = array.values().as_primitive::<Int32Type>();
+ /// assert_eq!(values, &Int32Array::from(vec![Some(1), Some(2), Some(3),
None]));
+ /// ```
+ ///
+ /// This is an alternative API to appending directly to [`Self::values`]
and
+ /// delimiting the result with [`Self::append`]
+ ///
+ /// ```
+ /// # use arrow_array::builder::{Int32Builder, ListBuilder};
+ /// # use arrow_array::cast::AsArray;
+ /// # use arrow_array::{Array, Int32Array};
+ /// # use arrow_array::types::Int32Type;
+ /// let mut builder = ListBuilder::new(Int32Builder::new());
+ ///
+ /// builder.values().append_value(1);
+ /// builder.values().append_value(2);
+ /// builder.values().append_value(3);
+ /// builder.append(true);
+ /// builder.append(true);
+ /// builder.values().append_null();
+ /// builder.append(true);
+ ///
+ /// let array = builder.finish();
+ /// assert_eq!(array.len(), 3);
+ ///
+ /// assert_eq!(array.value_offsets(), &[0, 3, 3, 4]);
+ /// let values = array.values().as_primitive::<Int32Type>();
+ /// assert_eq!(values, &Int32Array::from(vec![Some(1), Some(2), Some(3),
None]));
+ /// ```
+ #[inline]
+ pub fn append_value<I, V>(&mut self, i: I)
+ where
+ T: Extend<Option<V>>,
+ I: IntoIterator<Item = Option<V>>,
+ {
+ self.extend(std::iter::once(Some(i)))
Review Comment:
At least in some basic experiments LLVM seems to be able to optimise this as
one would hope
https://rust.godbolt.org/z/zcxzqzf59
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