etcdserver: preallocate slice in apply

Signed-off-by: Gyu-Ho Lee <gyuhox@gmail.com>

etcdserver/apply.go

@@ -224,8 +224,9 @@ func (a *applierV3backend) DeleteRange(txn mvcc.TxnWrite, dr *pb.DeleteRangeRequ
 			return nil, err
 		}
 		if rr != nil {
+			resp.PrevKvs = make([]*mvccpb.KeyValue, len(rr.KVs))
 			for i := range rr.KVs {
-				resp.PrevKvs = append(resp.PrevKvs, &rr.KVs[i])
+				resp.PrevKvs[i] = &rr.KVs[i]
 			}
 		}
 	}
@@ -319,11 +320,12 @@ func (a *applierV3backend) Range(txn mvcc.TxnRead, r *pb.RangeRequest) (*pb.Rang
 
 	resp.Header.Revision = rr.Rev
 	resp.Count = int64(rr.Count)
+	resp.Kvs = make([]*mvccpb.KeyValue, len(rr.KVs))
 	for i := range rr.KVs {
 		if r.KeysOnly {
 			rr.KVs[i].Value = nil
 		}
-		resp.Kvs = append(resp.Kvs, &rr.KVs[i])
+		resp.Kvs[i] = &rr.KVs[i]
 	}
 	return resp, nil
 }