undo sort_key() returning Cow

src/table/schema.rs

@@ -1,5 +1,3 @@
-use std::borrow::Cow;
-
 use serde::{Deserialize, Serialize};
 
 use garage_db as db;
@@ -38,24 +36,18 @@ impl PartitionKey for FixedBytes32 {
 /// Trait for field used to sort data
 pub trait SortKey: Clone + Serialize + for<'de> Deserialize<'de> + Send + Sync + 'static {
 	/// Get the key used to sort
-	fn sort_key(&self) -> Cow<'_, [u8]>;
+	fn sort_key(&self) -> &[u8];
 }
 
 impl SortKey for String {
-	fn sort_key(&self) -> Cow<'_, [u8]> {
-		Cow::from(self.as_bytes())
+	fn sort_key(&self) -> &[u8] {
+		self.as_bytes()
 	}
 }
 
 impl SortKey for FixedBytes32 {
-	fn sort_key(&self) -> Cow<'_, [u8]> {
-		Cow::from(self.as_slice())
-	}
-}
-
-impl SortKey for u32 {
-	fn sort_key(&self) -> Cow<'_, [u8]> {
-		Cow::from(u32::to_be_bytes(*self).to_vec())
+	fn sort_key(&self) -> &[u8] {
+		self.as_slice()
 	}
 }