style(compress): clarify stored width selection contracts

Signed-off-by: Connor Tsui <connor.tsui20@gmail.com>

Author: connortsui20

vortex-array/src/arrays/narrow/encoding.rs

@@ -56,9 +56,10 @@ impl NarrowArray {
         if !ptype.is_int() || ptype.byte_width() == 1 {
             return Ok(array);
         }
+
         let bounds = min_max(array.as_ref(), ctx, NumericalAggregateOpts::default())?;
         let storage_type = if let Some(bounds) = bounds {
-            let smallest = if ptype.is_signed_int() {
+            let (min_type, max_type) = if ptype.is_signed_int() {
                 (
                     PType::min_signed_ptype_for_value(i64::try_from(&bounds.min)?),
                     PType::min_signed_ptype_for_value(i64::try_from(&bounds.max)?),
@@ -69,16 +70,17 @@ impl NarrowArray {
                     PType::min_unsigned_ptype_for_value(u64::try_from(&bounds.max)?),
                 )
             };
-            if smallest.0.byte_width() >= smallest.1.byte_width() {
-                smallest.0
+            if min_type.byte_width() >= max_type.byte_width() {
+                min_type
             } else {
-                smallest.1
+                max_type
             }
         } else if ptype.is_signed_int() {
             PType::I8
         } else {
             PType::U8
         };
+
         if storage_type.byte_width() >= ptype.byte_width() {
             return Ok(array);
         }

vortex-btrblocks/tests/narrow.rs

@@ -2,6 +2,9 @@
 // SPDX-FileCopyrightText: Copyright the Vortex contributors
 
 //! Preview gating and codec cascades retain Narrow's logical dtype on the wire.
+//!
+//! Core and CUDA presets exclude Narrow wrappers. Serialization round trips also cover signed
+//! internal buffers whose dtypes are selected by the compressor.
 
 #![cfg(test)]
 
@@ -57,7 +60,7 @@ fn session(preview: bool) -> VortexResult<VortexSession> {
 #[rstest]
 #[case::core(false)]
 #[case::preview(true)]
-fn compression_roundtrip(#[case] preview: bool) -> VortexResult<()> {
+fn test_compression_roundtrip(#[case] preview: bool) -> VortexResult<()> {
     let session = session(preview)?;
     let mut ctx = session.create_execution_ctx();
     let input = PrimitiveArray::from_iter((0..8192u64).map(|i| i % 128)).into_array();
@@ -95,7 +98,7 @@ fn compression_roundtrip(#[case] preview: bool) -> VortexResult<()> {
 }
 
 #[test]
-fn cuda_preset_excludes_narrow() -> VortexResult<()> {
+fn test_cuda_preset_excludes_narrow() -> VortexResult<()> {
     let session = session(true)?;
     let mut ctx = session.create_execution_ctx();
     let input = PrimitiveArray::from_iter((0..8192u64).map(|i| i % 128)).into_array();
@@ -110,7 +113,7 @@ fn cuda_preset_excludes_narrow() -> VortexResult<()> {
 }
 
 #[test]
-fn internal_signed_buffers_roundtrip() -> VortexResult<()> {
+fn test_internal_signed_buffers_roundtrip() -> VortexResult<()> {
     let session = session(false)?;
     vortex_fsst::initialize(&session);
     #[cfg(feature = "pco")]

vortex-compressor/src/compressor/cascade.rs

@@ -93,6 +93,7 @@ impl CascadingCompressor {
             {
                 return NarrowArray::encode(primitive.into_owned(), exec_ctx);
             }
+
             return Ok(child.clone());
         }
 
@@ -134,11 +135,13 @@ impl CascadingCompressor {
                 if compressed.dtype() == &dtype {
                     return Ok(compressed);
                 }
+
                 if let Some(constant) = compressed.as_opt::<Constant>() {
                     return Ok(
                         ConstantArray::new(constant.scalar().cast(&dtype)?, len).into_array()
                     );
                 }
+
                 Ok(NarrowArray::try_new(compressed, dtype)?.into_array())
             }
             Canonical::Decimal(decimal) => {

vortex-compressor/src/compressor/mod.rs

@@ -81,6 +81,7 @@ impl CascadingCompressor {
     /// disabled by default and does not consume a level of the codec cascade budget.
     pub fn with_narrow_integers(mut self, enabled: bool) -> Self {
         self.narrow_integers = enabled;
+
         self
     }
 }

vortex-compressor/src/compressor/tests/mod.rs

@@ -2,6 +2,9 @@
 // SPDX-FileCopyrightText: Copyright the Vortex contributors
 
 //! Compression selection, cascades, and logical dtype preservation.
+//!
+//! Scheme fixtures isolate selection and exclusion rules. Narrow cases separately check the
+//! optional width reduction before codec selection.
 
 mod narrow;
 

vortex-compressor/src/compressor/tests/narrow.rs

@@ -2,6 +2,9 @@
 // SPDX-FileCopyrightText: Copyright the Vortex contributors
 
 //! Integer narrowing precedes codec selection and preserves the input dtype.
+//!
+//! These cases use a compressor without schemes to isolate width selection. Constants and values
+//! that need the full logical width exercise paths that do not require a Narrow wrapper.
 
 use rstest::rstest;
 use vortex_array::IntoArray;
@@ -21,7 +24,7 @@ use crate::CascadingCompressor;
 #[rstest]
 #[case::disabled(false)]
 #[case::enabled(true)]
-fn integer_width(#[case] enabled: bool) -> VortexResult<()> {
+fn test_integer_width(#[case] enabled: bool) -> VortexResult<()> {
     let mut ctx = array_session().create_execution_ctx();
     let input = buffer![-128i64, 0, 127].into_array();
     let compressor = CascadingCompressor::new(vec![]).with_narrow_integers(enabled);
@@ -44,7 +47,7 @@ fn integer_width(#[case] enabled: bool) -> VortexResult<()> {
 #[rstest]
 #[case::constant(PrimitiveArray::from_iter([127i64; 1024]))]
 #[case::all_null(PrimitiveArray::from_option_iter([None::<i64>; 3]))]
-fn constant_dtype(#[case] input: PrimitiveArray) -> VortexResult<()> {
+fn test_constant_dtype(#[case] input: PrimitiveArray) -> VortexResult<()> {
     let mut ctx = array_session().create_execution_ctx();
     let input = input.into_array();
     let compressor = CascadingCompressor::new(vec![]).with_narrow_integers(true);
@@ -58,7 +61,7 @@ fn constant_dtype(#[case] input: PrimitiveArray) -> VortexResult<()> {
 }
 
 #[test]
-fn full_width_values() -> VortexResult<()> {
+fn test_full_width_values() -> VortexResult<()> {
     let mut ctx = array_session().create_execution_ctx();
     let input = buffer![i64::MIN, i64::MAX].into_array();
     let result = CascadingCompressor::new(vec![])

vortex-edition/src/declarations/preview/v2026_10.rs

@@ -2,6 +2,9 @@
 // SPDX-FileCopyrightText: Copyright the Vortex contributors
 
 //! The October 2026 preview edition adding Narrow integer arrays.
+//!
+//! This declaration permits Narrow on the wire for sessions that enable it. Earlier preview
+//! and core editions retain their existing membership.
 
 use crate::Edition;
 use crate::EditionDeclaration;