Alpha: use recursive removal when possible

src/proto/alpha/reward_storage.ml

@@ -47,10 +47,11 @@ let pay_rewards_for_cycle c cycle =
         match c with
         | Error _ -> Lwt.return c
         | Ok c ->
-            Storage.Rewards.Amount.remove (c, cycle) delegate >>= fun c ->
             Contract_storage.credit c
               (Contract_repr.default_contract delegate)
-              amount)
+              amount) >>=? fun c ->
+  Storage.Rewards.Amount.clear (c, cycle) >>= fun c ->
+  return c
 
 let pay_due_rewards c =
   let timestamp = Raw_context.current_timestamp c in

src/proto/alpha/roll_storage.ml

@@ -18,15 +18,9 @@ let get_contract_delegate c contract =
   | None -> Storage.Contract.Delegate.get_option c contract
 
 let clear_cycle c cycle =
-  Storage.Roll.Last_for_cycle.get c cycle >>=? fun last ->
   Storage.Roll.Last_for_cycle.delete c cycle >>=? fun c ->
-  let rec loop c roll =
-    if Roll_repr.(roll = last) then
-      return c
-    else
-      Storage.Roll.Owner_for_cycle.delete (c, cycle) roll >>=? fun c ->
-      loop c (Roll_repr.succ roll) in
-  loop c Roll_repr.first
+  Storage.Roll.Owner_for_cycle.clear (c, cycle) >>= fun c ->
+  return c
 
 let fold ctxt ~f init =
   Storage.Roll.Next.get ctxt >>=? fun last ->