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new 4778077d53 [Variant] Add `VariantArrayBuilder::append_nulls` API
(#9685)
4778077d53 is described below
commit 4778077d53a6c1072fa8768bc29a0362a89b5f7e
Author: Konstantin Tarasov <[email protected]>
AuthorDate: Fri Apr 10 14:51:15 2026 -0400
[Variant] Add `VariantArrayBuilder::append_nulls` API (#9685)
# Which issue does this PR close?
- Closes #9684.
# Rationale for this change
Check issue
# What changes are included in this PR?
- Add `VariantArrayBuilder::append_nulls`
- Add unit test
- add fast paths for `cast_to_variant_with_options` and
`string_array_to_variant`
# Are these changes tested?
Yes, added a unit test
# Are there any user-facing changes?
A new public API
---
parquet-variant-compute/src/cast_to_variant.rs | 7 +++++
.../src/variant_array_builder.rs | 30 ++++++++++++++++++++++
2 files changed, 37 insertions(+)
diff --git a/parquet-variant-compute/src/cast_to_variant.rs
b/parquet-variant-compute/src/cast_to_variant.rs
index b6c968b067..1b26ffe07d 100644
--- a/parquet-variant-compute/src/cast_to_variant.rs
+++ b/parquet-variant-compute/src/cast_to_variant.rs
@@ -58,6 +58,13 @@ pub fn cast_to_variant_with_options(
input: &dyn Array,
options: &CastOptions,
) -> Result<VariantArray, ArrowError> {
+ // Fast path: any all-null input maps to an all-null VariantArray.
+ if input.null_count() == input.len() {
+ let mut array_builder = VariantArrayBuilder::new(input.len());
+ array_builder.append_nulls(input.len());
+ return Ok(array_builder.build());
+ }
+
// Create row builder for the input array type
let mut row_builder = make_arrow_to_variant_row_builder(input.data_type(),
input, options)?;
diff --git a/parquet-variant-compute/src/variant_array_builder.rs
b/parquet-variant-compute/src/variant_array_builder.rs
index 86ece00100..f6b95c881a 100644
--- a/parquet-variant-compute/src/variant_array_builder.rs
+++ b/parquet-variant-compute/src/variant_array_builder.rs
@@ -156,6 +156,18 @@ impl VariantArrayBuilder {
self.value_offsets.push(self.value_builder.offset());
}
+ /// Appends `n` null rows to the builder.
+ pub fn append_nulls(&mut self, n: usize) {
+ self.nulls.append_n_nulls(n);
+ // The subfields are expected to be non-nullable according to the
parquet variant spec.
+ let metadata_offset = self.metadata_builder.offset();
+ let value_offset = self.value_builder.offset();
+ self.metadata_offsets
+ .extend(std::iter::repeat_n(metadata_offset, n));
+ self.value_offsets
+ .extend(std::iter::repeat_n(value_offset, n));
+ }
+
/// Append the [`Variant`] to the builder as the next row
pub fn append_variant(&mut self, variant: Variant) {
ValueBuilder::append_variant(self.parent_state(), variant);
@@ -526,6 +538,24 @@ mod test {
assert_eq!(list.len(), 2);
}
+ #[test]
+ fn test_variant_array_builder_append_nulls() {
+ let mut builder = VariantArrayBuilder::new(6);
+ builder.append_variant(Variant::from(1i32));
+ builder.append_nulls(0); // should be a no-op
+ builder.append_nulls(3);
+ builder.append_variant(Variant::from(2i32));
+
+ let variant_array = builder.build();
+
+ assert_eq!(variant_array.len(), 5);
+ assert_eq!(variant_array.value(0), Variant::from(1i32));
+ assert!(variant_array.is_null(1));
+ assert!(variant_array.is_null(2));
+ assert!(variant_array.is_null(3));
+ assert_eq!(variant_array.value(4), Variant::from(2i32));
+ }
+
#[test]
fn test_extend_variant_array_builder() {
let mut b = VariantArrayBuilder::new(3);
