Faster Clone() in kv/key.go (#11957)

kv/key.go

@@ -24,7 +24,7 @@ type Key []byte
 // Next returns the next key in byte-order.
 func (k Key) Next() Key {
 	// add 0x0 to the end of key
-	buf := make([]byte, len([]byte(k))+1)
+	buf := make([]byte, len(k)+1)
 	copy(buf, []byte(k))
 	return buf
 }
@@ -41,7 +41,7 @@ func (k Key) Next() Key {
 // If we seek 'rowkey1' Next, we will get 'rowkey1_column1'.
 // If we seek 'rowkey1' PrefixNext, we will get 'rowkey2'.
 func (k Key) PrefixNext() Key {
-	buf := make([]byte, len([]byte(k)))
+	buf := make([]byte, len(k))
 	copy(buf, []byte(k))
 	var i int
 	for i = len(k) - 1; i >= 0; i-- {
@@ -68,9 +68,11 @@ func (k Key) HasPrefix(prefix Key) bool {
 	return bytes.HasPrefix(k, prefix)
 }
 
-// Clone returns a copy of the Key.
+// Clone returns a deep copy of the Key.
 func (k Key) Clone() Key {
-	return append([]byte(nil), k...)
+	ck := make([]byte, len(k))
+	copy(ck, []byte(k))
+	return ck
 }
 
 // String implements fmt.Stringer interface.