Simplify decimal byte-parts array helpers

Move array helpers onto a crate-private extension trait, preserve decimal
precision and scale when replacing the MSP, and group slicing with the
other compute operations. Inline canonical execution and select scalar
storage directly from the lower-part count.

Signed-off-by: Matt Katz <mhkatz97@gmail.com>

Author: mhk197

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

@@ -10,8 +10,8 @@ use vortex_array::scalar_fn::fns::cast::CastReduce;
 use vortex_error::VortexResult;
 
 use crate::DecimalByteParts;
+use crate::decimal_byte_parts::DecimalBytePartsArrayExt;
 use crate::decimal_byte_parts::DecimalBytePartsArraySlotsExt;
-use crate::decimal_byte_parts::with_msp;
 
 impl CastReduce for DecimalByteParts {
     fn cast(array: ArrayView<'_, Self>, dtype: &DType) -> VortexResult<Option<ArrayRef>> {
@@ -20,7 +20,7 @@ impl CastReduce for DecimalByteParts {
             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 {
+        let DType::Decimal(_, target_nullability) = dtype else {
             // Cannot cast decimal to non-decimal types - delegate to canonical form
             return Ok(None);
         };
@@ -30,7 +30,7 @@ impl CastReduce for DecimalByteParts {
             .msp()
             .cast(array.msp().dtype().with_nullability(*target_nullability))?;
 
-        with_msp(array, new_msp, *target_decimal).map(|a| Some(a.into_array()))
+        array.with_msp(new_msp).map(|a| Some(a.into_array()))
     }
 }
 

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

@@ -9,11 +9,13 @@ use vortex_error::VortexResult;
 use vortex_mask::Mask;
 
 use crate::DecimalByteParts;
-use crate::decimal_byte_parts::map_parts;
+use crate::decimal_byte_parts::DecimalBytePartsArrayExt;
 
 impl FilterReduce for DecimalByteParts {
     fn filter(array: ArrayView<'_, Self>, mask: &Mask) -> VortexResult<Option<ArrayRef>> {
-        map_parts(array, |part| part.filter(mask.clone())).map(|d| Some(d.into_array()))
+        array
+            .map_parts(|part| part.filter(mask.clone()))
+            .map(|d| Some(d.into_array()))
     }
 }
 

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

@@ -9,15 +9,14 @@ use vortex_array::scalar_fn::fns::mask::MaskReduce;
 use vortex_error::VortexResult;
 
 use crate::DecimalByteParts;
+use crate::decimal_byte_parts::DecimalBytePartsArrayExt;
 use crate::decimal_byte_parts::DecimalBytePartsArraySlotsExt;
-use crate::decimal_byte_parts::decimal_dtype;
-use crate::decimal_byte_parts::with_msp;
 
 impl MaskReduce for DecimalByteParts {
     fn mask(array: ArrayView<'_, Self>, mask: &ArrayRef) -> VortexResult<Option<ArrayRef>> {
         // Validity lives in the MSP, so only that part needs masking: the lower parts hold
         // undefined bits in null slots, which is exactly what a masked-out row is.
         let masked_msp = MaskExpr::try_new(array.msp().clone(), mask.clone())?.into_array();
-        with_msp(array, masked_msp, decimal_dtype(array)).map(|a| Some(a.into_array()))
+        array.with_msp(masked_msp).map(|a| Some(a.into_array()))
     }
 }

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

@@ -7,6 +7,7 @@ mod filter;
 pub(crate) mod is_constant;
 pub(crate) mod kernel;
 mod mask;
+mod slice;
 mod take;
 
 #[cfg(test)]

…te-parts/src/decimal_byte_parts/slice.rs …/src/decimal_byte_parts/compute/slice.rsencodings/decimal-byte-parts/src/decimal_byte_parts/slice.rs renamed to encodings/decimal-byte-parts/src/decimal_byte_parts/compute/slice.rs encodings/decimal-byte-parts/src/decimal_byte_parts/slice.rs renamed to encodings/decimal-byte-parts/src/decimal_byte_parts/compute/slice.rs

@@ -10,10 +10,12 @@ use vortex_array::arrays::slice::SliceReduce;
 use vortex_error::VortexResult;
 
 use crate::DecimalByteParts;
-use crate::decimal_byte_parts::map_parts;
+use crate::decimal_byte_parts::DecimalBytePartsArrayExt;
 
 impl SliceReduce for DecimalByteParts {
     fn slice(array: ArrayView<'_, Self>, range: Range<usize>) -> VortexResult<Option<ArrayRef>> {
-        map_parts(array, |part| part.slice(range.clone())).map(|d| Some(d.into_array()))
+        array
+            .map_parts(|part| part.slice(range.clone()))
+            .map(|d| Some(d.into_array()))
     }
 }

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

@@ -8,8 +8,8 @@ use vortex_array::arrays::dict::TakeReduce;
 use vortex_error::VortexResult;
 
 use crate::DecimalByteParts;
+use crate::decimal_byte_parts::DecimalBytePartsArrayExt;
 use crate::decimal_byte_parts::DecimalBytePartsArraySlotsExt;
-use crate::decimal_byte_parts::map_parts;
 
 impl TakeReduce for DecimalByteParts {
     /// Taking wraps each part in a `Dict` without reading any buffer, so it reduces rather
@@ -22,7 +22,9 @@ impl TakeReduce for DecimalByteParts {
             return Ok(None);
         }
 
-        map_parts(array, |part| part.take(indices.clone())).map(|a| Some(a.into_array()))
+        array
+            .map_parts(|part| part.take(indices.clone()))
+            .map(|a| Some(a.into_array()))
     }
 }