Use Cow<[u8]> for sort keys

src/table/data.rs

@@ -347,9 +347,7 @@ impl<F: TableSchema, R: TableReplication> TableData<F, R> {
 	// ---- Utility functions ----
 
 	pub fn tree_key(&self, p: &F::P, s: &F::S) -> Vec<u8> {
-		let mut ret = p.hash().to_vec();
-		ret.extend(s.sort_key());
-		ret
+		[p.hash().as_slice(), s.sort_key().as_ref()].concat()
 	}
 
 	pub fn decode_entry(&self, bytes: &[u8]) -> Result<F::E, Error> {

src/table/schema.rs

@@ -1,3 +1,5 @@
+use std::borrow::Cow;
+
 use serde::{Deserialize, Serialize};
 
 use garage_db as db;
@@ -32,18 +34,18 @@ 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) -> &[u8];
+	fn sort_key(&self) -> Cow<'_, [u8]>;
 }
 
 impl SortKey for String {
-	fn sort_key(&self) -> &[u8] {
-		self.as_bytes()
+	fn sort_key(&self) -> Cow<'_, [u8]> {
+		Cow::from(self.as_bytes())
 	}
 }
 
 impl SortKey for FixedBytes32 {
-	fn sort_key(&self) -> &[u8] {
-		self.as_slice()
+	fn sort_key(&self) -> Cow<'_, [u8]> {
+		Cow::from(self.as_slice())
 	}
 }
 

src/table/util.rs

@@ -1,3 +1,5 @@
+use std::borrow::Cow;
+
 use serde::{Deserialize, Serialize};
 
 use garage_util::data::*;
@@ -7,8 +9,8 @@ use crate::schema::*;
 #[derive(Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub struct EmptyKey;
 impl SortKey for EmptyKey {
-	fn sort_key(&self) -> &[u8] {
-		&[]
+	fn sort_key(&self) -> Cow<'_, [u8]> {
+		Cow::from(&[][..])
 	}
 }
 impl PartitionKey for EmptyKey {