pola-rs/polars · error

null buffer should be there

Error message

null buffer should be there

What it means

take_agg_primitive_iter_unchecked_count_nulls requires the array to have a validity bitmap because it must count nulls per window; it calls .expect("null buffer should be there") and panics when arr.validity() is None, i.e. the kernel was invoked on a no-nulls array.

Solutions

1. Call the no-nulls variant of the take-agg kernel when validity() is None
2. Reify the validity bitmap (e.g. via rechunk/with_validity) before using this kernel
3. Add a check that selects the correct kernel based on arr.validity()

When it happens

Trigger: Thrown at crates/polars-arrow/src/legacy/kernels/take_agg/mod.rs:67 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of pola-rs/polars@fe841f959e (2026-09-18). Data as JSON: /api/errors/6f37fa11d2127a14. Report an issue: GitHub.

Appendix: source

Thrown at crates/polars-arrow/src/legacy/kernels/take_agg/mod.rs:67

/// Take kernel for single chunk and an iterator as index.
/// # Safety
/// caller must ensure iterators indexes are in bounds
#[inline]
pub unsafe fn take_agg_primitive_iter_unchecked_count_nulls<
    T: NativeType + ToPrimitive,
    I: IntoIterator<Item = usize>,
    TOut,
    F: Fn(TOut, T) -> TOut,
>(
    arr: &PrimitiveArray<T>,
    indices: I,
    init: TOut,
    f: F,
    len: IdxSize,
) -> Option<(TOut, IdxSize)> {
    let array_values = arr.values().as_slice();
    let validity = arr.validity().expect("null buffer should be there");

    let mut null_count = 0 as IdxSize;
    let out = indices.into_iter().fold(init, |acc, idx| {
        if validity.get_bit_unchecked(idx) {
            f(acc, *array_values.get_unchecked(idx))
        } else {
            null_count += 1;
            acc
        }
    });
    if null_count == len {
        None
    } else {
        Some((out, null_count))
    }
}

/// Take kernel for single chunk and an iterator as index.

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