Validity casting doesn't hide usage of execution context

AGENTS.md

@@ -64,11 +64,14 @@ Examples:
 cargo nextest run -p vortex-array
 make -C docs doctest
 uv run --all-packages pytest vortex-python/test
+cargo test --doc
 ```
 
 Run docs doctests from the docs directory with `make -C docs doctest` so the correct Sphinx
 Makefile target is used.
 
+If you touch documentation run doc tests via `cargo test --doc`.
+
 ## Linting, Formatting, and Generated Files
 
 Run verification that matches the files changed. Do not run expensive Rust checks for changes that

encodings/alp/src/alp/compute/cast.rs

@@ -6,7 +6,6 @@ use vortex_array::ArrayView;
 use vortex_array::IntoArray;
 use vortex_array::builtins::ArrayBuiltins;
 use vortex_array::dtype::DType;
-use vortex_array::patches::Patches;
 use vortex_array::scalar_fn::fns::cast::CastReduce;
 use vortex_error::VortexResult;
 
@@ -17,41 +16,29 @@ use crate::alp::ALP;
 impl CastReduce for ALP {
     fn cast(array: ArrayView<'_, Self>, dtype: &DType) -> VortexResult<Option<ArrayRef>> {
         // Check if this is just a nullability change
-        if array.dtype().eq_ignore_nullability(dtype) {
-            // For nullability-only changes, we can avoid decoding
-            // Cast the encoded array (integers) to handle nullability
-            let new_encoded = array.encoded().cast(
-                array
-                    .encoded()
-                    .dtype()
-                    .with_nullability(dtype.nullability()),
-            )?;
-
-            let new_patches = array
-                .patches()
-                .map(|p| {
-                    if p.values().dtype() == dtype {
-                        Ok(p)
-                    } else {
-                        Patches::new(
-                            p.array_len(),
-                            p.offset(),
-                            p.indices().clone(),
-                            p.values().cast(dtype.clone())?,
-                            p.chunk_offsets().clone(),
-                        )
-                    }
-                })
-                .transpose()?;
-
-            // SAFETY: casting nullability doesn't alter the invariants
-            unsafe {
-                Ok(Some(
-                    ALP::new_unchecked(new_encoded, array.exponents(), new_patches).into_array(),
-                ))
-            }
-        } else {
-            Ok(None)
+        if !array.dtype().eq_ignore_nullability(dtype) {
+            return Ok(None);
+        }
+
+        // For nullability-only changes, we can avoid decoding
+        // Cast the encoded array (integers) to handle nullability
+        let new_encoded = array.encoded().cast(
+            array
+                .encoded()
+                .dtype()
+                .with_nullability(dtype.nullability()),
+        )?;
+
+        let new_patches = array
+            .patches()
+            .map(|p| p.map_values(|v| v.cast(dtype.clone())))
+            .transpose()?;
+
+        // SAFETY: casting nullability doesn't alter the invariants
+        unsafe {
+            Ok(Some(
+                ALP::new_unchecked(new_encoded, array.exponents(), new_patches).into_array(),
+            ))
         }
     }
 }

encodings/alp/src/alp_rd/compute/cast.rs

@@ -4,8 +4,6 @@
 use vortex_array::ArrayRef;
 use vortex_array::ArrayView;
 use vortex_array::IntoArray;
-use vortex_array::LEGACY_SESSION;
-use vortex_array::VortexSessionExecute;
 use vortex_array::builtins::ArrayBuiltins;
 use vortex_array::dtype::DType;
 use vortex_array::scalar_fn::fns::cast::CastReduce;
@@ -16,38 +14,35 @@ use crate::alp_rd::ALPRD;
 
 impl CastReduce for ALPRD {
     fn cast(array: ArrayView<'_, Self>, dtype: &DType) -> VortexResult<Option<ArrayRef>> {
-        // ALPRDArray stores floating-point values, so only cast between float types
-        // or if just changing nullability
-
         // Check if this is just a nullability change
-        if array.dtype().eq_ignore_nullability(dtype) {
-            // For nullability-only changes, we need to cast the left_parts array
-            // since it carries the validity information
-            let new_left_parts = array.left_parts().cast(
-                array
-                    .left_parts()
-                    .dtype()
-                    .with_nullability(dtype.nullability()),
-            )?;
+        if !array.dtype().eq_ignore_nullability(dtype) {
+            return Ok(None);
+        }
+
+        // For nullability-only changes, we need to cast the left_parts array
+        // since it carries the validity information
+        let new_left_parts = array.left_parts().cast(
+            array
+                .left_parts()
+                .dtype()
+                .with_nullability(dtype.nullability()),
+        )?;
 
-            // NOTE: `CastReduce::cast` has a fixed trait signature without `ExecutionCtx`, so we
-            // construct a legacy ctx locally at this trait boundary.
-            return Ok(Some(
-                ALPRD::try_new(
+        // NOTE: `CastReduce::cast` has a fixed trait signature without `ExecutionCtx`, so we
+        // construct a legacy ctx locally at this trait boundary.
+        Ok(Some(
+            unsafe {
+                ALPRD::new_unchecked(
                     dtype.clone(),
                     new_left_parts,
                     array.left_parts_dictionary().clone(),
                     array.right_parts().clone(),
                     array.right_bit_width(),
                     array.left_parts_patches(),
-                    &mut LEGACY_SESSION.create_execution_ctx(),
-                )?
-                .into_array(),
-            ));
-        }
-
-        // For other casts (e.g., f32 to f64), decode to canonical and let PrimitiveArray handle it
-        Ok(None)
+                )
+            }
+            .into_array(),
+        ))
     }
 }
 
@@ -99,12 +94,17 @@ mod tests {
         let encoder = RDEncoder::new(&values);
         let alprd = encoder.encode(arr.as_view(), &mut ctx);
 
-        // Cast to NonNullable should fail since we have nulls
+        // Cast to NonNullable should fail since we have nulls. The failure surfaces during
+        // execution since the reduce path defers when the validity stat is not cached.
         let result = alprd
             .clone()
             .into_array()
-            .cast(DType::Primitive(PType::F64, Nullability::NonNullable));
-        assert!(result.is_err());
+            .cast(DType::Primitive(PType::F64, Nullability::NonNullable))
+            .and_then(|a| {
+                a.execute::<PrimitiveArray>(&mut ctx)
+                    .map(|p| p.into_array())
+            });
+        assert!(result.is_err(), "Expected error, got: {result:?}");
 
         // Cast to same type with Nullable should succeed
         let casted = alprd

encodings/bytebool/public-api.lock

@@ -64,6 +64,10 @@ impl vortex_array::arrays::slice::SliceReduce for vortex_bytebool::ByteBool
 
 pub fn vortex_bytebool::ByteBool::slice(array: vortex_array::array::view::ArrayView<'_, Self>, range: core::ops::range::Range<usize>) -> vortex_error::VortexResult<core::option::Option<vortex_array::array::erased::ArrayRef>>
 
+impl vortex_array::scalar_fn::fns::cast::kernel::CastKernel for vortex_bytebool::ByteBool
+
+pub fn vortex_bytebool::ByteBool::cast(array: vortex_array::array::view::ArrayView<'_, Self>, dtype: &vortex_array::dtype::DType, ctx: &mut vortex_array::executor::ExecutionCtx) -> vortex_error::VortexResult<core::option::Option<vortex_array::array::erased::ArrayRef>>
+
 impl vortex_array::scalar_fn::fns::cast::kernel::CastReduce for vortex_bytebool::ByteBool
 
 pub fn vortex_bytebool::ByteBool::cast(array: vortex_array::array::view::ArrayView<'_, Self>, dtype: &vortex_array::dtype::DType) -> vortex_error::VortexResult<core::option::Option<vortex_array::array::erased::ArrayRef>>

encodings/bytebool/src/compute.rs

@@ -11,6 +11,7 @@ use vortex_array::arrays::dict::TakeExecute;
 use vortex_array::buffer::BufferHandle;
 use vortex_array::dtype::DType;
 use vortex_array::match_each_integer_ptype;
+use vortex_array::scalar_fn::fns::cast::CastKernel;
 use vortex_array::scalar_fn::fns::cast::CastReduce;
 use vortex_array::scalar_fn::fns::mask::MaskReduce;
 use vortex_array::validity::Validity;
@@ -24,20 +25,43 @@ impl CastReduce for ByteBool {
         // ByteBool is essentially a bool array stored as bytes
         // The main difference from BoolArray is the storage format
         // For casting, we can decode to canonical (BoolArray) and let it handle the cast
-
         // If just changing nullability, we can optimize
-        if array.dtype().eq_ignore_nullability(dtype) {
-            let new_validity = array
-                .validity()?
-                .cast_nullability(dtype.nullability(), array.len())?;
+        if !dtype.is_boolean() {
+            return Ok(None);
+        }
+
+        let Some(new_validity) = array
+            .validity()?
+            .try_cast_nullability(dtype.nullability(), array.len())?
+        else {
+            return Ok(None);
+        };
+
+        Ok(Some(
+            ByteBool::new(array.buffer().clone(), new_validity).into_array(),
+        ))
+    }
+}
 
-            return Ok(Some(
-                ByteBool::new(array.buffer().clone(), new_validity).into_array(),
-            ));
+impl CastKernel for ByteBool {
+    fn cast(
+        array: ArrayView<'_, Self>,
+        dtype: &DType,
+        ctx: &mut ExecutionCtx,
+    ) -> VortexResult<Option<ArrayRef>> {
+        // Only handle nullability changes here; non-bool targets fall through to canonicalization.
+        if !dtype.is_boolean() {
+            return Ok(None);
         }
 
-        // For other casts, decode to canonical and let BoolArray handle it
-        Ok(None)
+        let new_validity =
+            array
+                .validity()?
+                .cast_nullability(dtype.nullability(), array.len(), ctx)?;
+
+        Ok(Some(
+            ByteBool::new(array.buffer().clone(), new_validity).into_array(),
+        ))
     }
 }
 

encodings/bytebool/src/kernel.rs

@@ -3,8 +3,11 @@
 
 use vortex_array::arrays::dict::TakeExecuteAdaptor;
 use vortex_array::kernel::ParentKernelSet;
+use vortex_array::scalar_fn::fns::cast::CastExecuteAdaptor;
 
 use crate::ByteBool;
 
-pub(crate) const PARENT_KERNELS: ParentKernelSet<ByteBool> =
-    ParentKernelSet::new(&[ParentKernelSet::lift(&TakeExecuteAdaptor(ByteBool))]);
+pub(crate) const PARENT_KERNELS: ParentKernelSet<ByteBool> = ParentKernelSet::new(&[
+    ParentKernelSet::lift(&CastExecuteAdaptor(ByteBool)),
+    ParentKernelSet::lift(&TakeExecuteAdaptor(ByteBool)),
+]);

encodings/decimal-byte-parts/src/decimal_byte_parts/compute/cast.rs

@@ -7,39 +7,31 @@ use vortex_array::IntoArray;
 use vortex_array::builtins::ArrayBuiltins;
 use vortex_array::dtype::DType;
 use vortex_array::scalar_fn::fns::cast::CastReduce;
-use vortex_error::VortexExpect;
 use vortex_error::VortexResult;
 
 use crate::DecimalByteParts;
 use crate::decimal_byte_parts::DecimalBytePartsArrayExt;
+
 impl CastReduce for DecimalByteParts {
     fn cast(array: ArrayView<'_, Self>, dtype: &DType) -> VortexResult<Option<ArrayRef>> {
+        // Check if this is just a nullability change
+        if !dtype.eq_ignore_nullability(array.dtype()) {
+            return Ok(None);
+        }
         // DecimalBytePartsArray can only have Decimal dtype, so we only handle decimal-to-decimal casts
         let DType::Decimal(target_decimal, target_nullability) = dtype else {
             // Cannot cast decimal to non-decimal types - delegate to canonical form
             return Ok(None);
         };
 
-        // Check if this is just a nullability change
-        if array
-            .dtype()
-            .as_decimal_opt()
-            .vortex_expect("must be a decimal dtype")
-            == target_decimal
-            && array.dtype().nullability() != *target_nullability
-        {
-            // Cast the msp array to handle nullability change
-            let new_msp = array
-                .msp()
-                .cast(array.msp().dtype().with_nullability(*target_nullability))?;
-
-            return Ok(Some(
-                DecimalByteParts::try_new(new_msp, *target_decimal)?.into_array(),
-            ));
-        }
+        // Cast the msp array to handle nullability change
+        let new_msp = array
+            .msp()
+            .cast(array.msp().dtype().with_nullability(*target_nullability))?;
 
-        // For precision/scale changes, decode to canonical and let DecimalArray handle it
-        Ok(None)
+        Ok(Some(
+            DecimalByteParts::try_new(new_msp, *target_decimal)?.into_array(),
+        ))
     }
 }
 

encodings/fastlanes/public-api.lock

@@ -186,6 +186,10 @@ impl vortex_array::arrays::slice::SliceReduce for vortex_fastlanes::BitPacked
 
 pub fn vortex_fastlanes::BitPacked::slice(array: vortex_array::array::view::ArrayView<'_, Self>, range: core::ops::range::Range<usize>) -> vortex_error::VortexResult<core::option::Option<vortex_array::array::erased::ArrayRef>>
 
+impl vortex_array::scalar_fn::fns::cast::kernel::CastKernel for vortex_fastlanes::BitPacked
+
+pub fn vortex_fastlanes::BitPacked::cast(array: vortex_array::array::view::ArrayView<'_, Self>, dtype: &vortex_array::dtype::DType, ctx: &mut vortex_array::executor::ExecutionCtx) -> vortex_error::VortexResult<core::option::Option<vortex_array::array::erased::ArrayRef>>
+
 impl vortex_array::scalar_fn::fns::cast::kernel::CastReduce for vortex_fastlanes::BitPacked
 
 pub fn vortex_fastlanes::BitPacked::cast(array: vortex_array::array::view::ArrayView<'_, Self>, dtype: &vortex_array::dtype::DType) -> vortex_error::VortexResult<core::option::Option<vortex_array::array::erased::ArrayRef>>

encodings/fastlanes/src/bitpacking/array/mod.rs

@@ -337,19 +337,25 @@ impl<T: TypedArrayRef<crate::BitPacked>> BitPackedArrayExt for T {}
 
 #[cfg(test)]
 mod test {
+    use std::sync::LazyLock;
+
     use vortex_array::IntoArray;
-    use vortex_array::LEGACY_SESSION;
     use vortex_array::VortexSessionExecute;
     use vortex_array::arrays::PrimitiveArray;
     use vortex_array::assert_arrays_eq;
+    use vortex_array::session::ArraySession;
     use vortex_buffer::Buffer;
+    use vortex_session::VortexSession;
 
     use crate::BitPackedData;
     use crate::bitpacking::array::BitPackedArrayExt;
 
+    static SESSION: LazyLock<VortexSession> =
+        LazyLock::new(|| VortexSession::empty().with::<ArraySession>());
+
     #[test]
     fn test_encode() {
-        let mut ctx = LEGACY_SESSION.create_execution_ctx();
+        let mut ctx = SESSION.create_execution_ctx();
         let values = [
             Some(1u64),
             None,
@@ -372,7 +378,7 @@ mod test {
 
     #[test]
     fn test_encode_too_wide() {
-        let mut ctx = LEGACY_SESSION.create_execution_ctx();
+        let mut ctx = SESSION.create_execution_ctx();
         let values = [Some(1u8), None, Some(1), None, Some(1), None];
         let uncompressed = PrimitiveArray::from_option_iter(values);
         let _packed = BitPackedData::encode(&uncompressed.clone().into_array(), 8, &mut ctx)
@@ -383,7 +389,7 @@ mod test {
 
     #[test]
     fn signed_with_patches() {
-        let mut ctx = LEGACY_SESSION.create_execution_ctx();
+        let mut ctx = SESSION.create_execution_ctx();
         let values: Buffer<i32> = (0i32..=512).collect();
         let parray = values.clone().into_array();