ALP decompress in place (#700)

encodings/alp/src/compress.rs

@@ -1,4 +1,3 @@
-use itertools::Itertools;
 use vortex::array::{PrimitiveArray, Sparse, SparseArray};
 use vortex::validity::Validity;
 use vortex::{Array, ArrayDType, ArrayDef, IntoArray, IntoArrayVariant};
@@ -61,11 +60,12 @@ pub fn alp_encode(parray: &PrimitiveArray) -> VortexResult<ALPArray> {
 
 pub fn decompress(array: ALPArray) -> VortexResult<PrimitiveArray> {
     let encoded = array.encoded().into_primitive()?;
+    let validity = encoded.validity();
 
     let decoded = match_each_alp_float_ptype!(array.dtype().try_into().unwrap(), |$T| {
         PrimitiveArray::from_vec(
-            decompress_primitive::<$T>(encoded.maybe_null_slice(), array.exponents()),
-            encoded.validity(),
+            decompress_primitive::<$T>(encoded.into_maybe_null_slice(), array.exponents()),
+            validity,
         )
     });
 
@@ -95,13 +95,13 @@ fn patch_decoded(array: PrimitiveArray, patches: &Array) -> VortexResult<Primiti
 }
 
 fn decompress_primitive<T: NativePType + ALPFloat>(
-    values: &[T::ALPInt],
+    values: Vec<T::ALPInt>,
     exponents: Exponents,
 ) -> Vec<T> {
     values
-        .iter()
-        .map(|&v| T::decode_single(v, exponents))
-        .collect_vec()
+        .into_iter()
+        .map(|v| T::decode_single(v, exponents))
+        .collect()
 }
 
 #[cfg(test)]