fix: avoid oob take for primitive

Signed-off-by: Andrew Duffy <[email protected]>

Author: a10y

vortex-array/src/arrays/primitive/compute/take/mod.rs

@@ -6,6 +6,7 @@ mod avx2;
 
 #[cfg(vortex_nightly)]
 mod portable;
+mod scalar;
 
 use std::sync::LazyLock;
 
@@ -48,7 +49,7 @@ static PRIMITIVE_TAKE_KERNEL: LazyLock<&'static dyn TakeImpl> = LazyLock::new(||
             }
         } else {
             // stable all other platforms: scalar kernel
-            &TakeKernelScalar
+            &scalar::TakeKernelScalar
         }
     }
 });
@@ -62,25 +63,6 @@ trait TakeImpl: Send + Sync {
     ) -> VortexResult<ArrayRef>;
 }
 
-#[allow(unused)]
-struct TakeKernelScalar;
-
-impl TakeImpl for TakeKernelScalar {
-    fn take(
-        &self,
-        array: &PrimitiveArray,
-        indices: &PrimitiveArray,
-        validity: Validity,
-    ) -> VortexResult<ArrayRef> {
-        match_each_native_ptype!(array.ptype(), |T| {
-            match_each_integer_ptype!(indices.ptype(), |I| {
-                let values = take_primitive_scalar(array.as_slice::<T>(), indices.as_slice::<I>());
-                Ok(PrimitiveArray::new(values, validity).into_array())
-            })
-        })
-    }
-}
-
 impl TakeKernel for PrimitiveVTable {
     fn take(&self, array: &PrimitiveArray, indices: &dyn Array) -> VortexResult<ArrayRef> {
         let DType::Primitive(ptype, null) = indices.dtype() else {
@@ -102,13 +84,6 @@ impl TakeKernel for PrimitiveVTable {
 
 register_kernel!(TakeKernelAdapter(PrimitiveVTable).lift());
 
-// Compiler may see this as unused based on enabled features
-#[allow(unused)]
-#[inline(always)]
-fn take_primitive_scalar<T: NativePType, I: IntegerPType>(array: &[T], indices: &[I]) -> Buffer<T> {
-    indices.iter().map(|idx| array[idx.as_()]).collect()
-}
-
 #[cfg(any(target_arch = "x86_64", target_arch = "x86"))]
 #[cfg(test)]
 mod test {

vortex-array/src/arrays/primitive/compute/take/scalar.rs

@@ -0,0 +1,111 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: Copyright the Vortex contributors
+
+use vortex_buffer::Buffer;
+use vortex_dtype::{IntegerPType, NativePType, match_each_integer_ptype, match_each_native_ptype};
+use vortex_error::VortexResult;
+
+use crate::arrays::PrimitiveArray;
+use crate::arrays::primitive::compute::take::TakeImpl;
+use crate::validity::Validity;
+use crate::vtable::ValidityHelper;
+use crate::{ArrayRef, IntoArray};
+
+#[allow(unused)]
+pub(super) struct TakeKernelScalar;
+
+impl TakeImpl for TakeKernelScalar {
+    #[allow(clippy::cognitive_complexity)]
+    fn take(
+        &self,
+        array: &PrimitiveArray,
+        indices: &PrimitiveArray,
+        validity: Validity,
+    ) -> VortexResult<ArrayRef> {
+        match_each_native_ptype!(array.ptype(), |T| {
+            match_each_integer_ptype!(indices.ptype(), |I| {
+                let indices_slice = indices.as_slice::<I>();
+                let indices_validity = indices.validity();
+                let values = if indices_validity.all_valid(indices_slice.len()) {
+                    // Fast path: indices have no nulls, safe to index directly
+                    take_primitive_scalar(array.as_slice::<T>(), indices_slice)
+                } else {
+                    // Slow path: indices may have nulls with garbage values
+                    take_primitive_scalar_with_nulls(
+                        array.as_slice::<T>(),
+                        indices_slice,
+                        indices_validity,
+                    )
+                };
+                Ok(PrimitiveArray::new(values, validity).into_array())
+            })
+        })
+    }
+}
+
+// Compiler may see this as unused based on enabled features
+#[allow(unused)]
+#[inline(always)]
+fn take_primitive_scalar<T: NativePType, I: IntegerPType>(array: &[T], indices: &[I]) -> Buffer<T> {
+    indices.iter().map(|idx| array[idx.as_()]).collect()
+}
+
+/// Slow path for take when indices may contain nulls with garbage values.
+/// Uses 0 as a safe index for null positions (the value will be masked out by validity).
+#[allow(unused)]
+#[inline(always)]
+fn take_primitive_scalar_with_nulls<T: NativePType, I: IntegerPType>(
+    array: &[T],
+    indices: &[I],
+    validity: &Validity,
+) -> Buffer<T> {
+    indices
+        .iter()
+        .enumerate()
+        .map(|(i, idx)| {
+            if validity.is_valid(i) {
+                array[idx.as_()]
+            } else {
+                T::zero()
+            }
+        })
+        .collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use vortex_buffer::buffer;
+
+    use crate::arrays::PrimitiveArray;
+    use crate::arrays::primitive::compute::take::TakeImpl;
+    use crate::arrays::primitive::compute::take::scalar::TakeKernelScalar;
+    use crate::validity::Validity;
+    use crate::{IntoArray, ToCanonical};
+
+    #[test]
+    fn test_scalar_basic() {
+        let values = buffer![1, 2, 3, 4, 5].into_array().to_primitive();
+        let indices = buffer![0, 1, 1, 2, 2, 3, 4].into_array().to_primitive();
+
+        let result = TakeKernelScalar
+            .take(&values, &indices, Validity::NonNullable)
+            .unwrap()
+            .to_primitive();
+        assert_eq!(result.as_slice::<i32>(), &[1, 2, 2, 3, 3, 4, 5]);
+    }
+
+    #[test]
+    fn test_scalar_with_nulls() {
+        let values = buffer![1, 2, 3, 4, 5].into_array().to_primitive();
+        let validity = Validity::from_iter([true, false, true, true, true]);
+        let indices = PrimitiveArray::new(buffer![0, 100, 2, 3, 4], validity.clone());
+
+        let result = TakeKernelScalar
+            .take(&values, &indices, validity.clone())
+            .unwrap()
+            .to_primitive();
+
+        assert_eq!(result.as_slice::<i32>(), &[1, 0, 3, 4, 5]);
+        assert_eq!(result.validity, validity);
+    }
+}