diff --git a/src/hanoi_merger.erl b/src/hanoi_merger.erl
index 6a67f24..0069b16 100644
--- a/src/hanoi_merger.erl
+++ b/src/hanoi_merger.erl
@@ -66,18 +66,21 @@ terminate(Count, Out) ->
 
     {ok, Count}.
 
-step({N, From}) ->
-    {N-1, From}.
+step(S) ->
+    step(S, 1).
+
+step({N, From}, Steps) ->
+    {N-Steps, From}.
 
 hibernate_scan(Keep) ->
     erlang:garbage_collect(),
     receive
         {step, From, HowMany} ->
-            {BT1, BT2, OutBin, IsLastLevel, AKVs, BKVs, Count} = erlang:binary_to_term( zlib:gunzip( Keep ) ),
-            scan(BT1, BT2, hanoi_writer:deserialize(OutBin), IsLastLevel, AKVs, BKVs, Count, {HowMany, From})
+            {BT1, BT2, OutBin, IsLastLevel, AKVs, BKVs, Count, N} = erlang:binary_to_term( zlib:gunzip( Keep ) ),
+            scan(BT1, BT2, hanoi_writer:deserialize(OutBin), IsLastLevel, AKVs, BKVs, Count, {N+HowMany, From})
     end.
 
-scan(BT1, BT2, Out, IsLastLevel, AKVs, BKVs, Count, {0, FromPID}) ->
+scan(BT1, BT2, Out, IsLastLevel, AKVs, BKVs, Count, {N, FromPID}) when N < 1, AKVs =/= [], BKVs =/= [] ->
     case FromPID of
         none ->
             ok;
@@ -87,11 +90,11 @@ scan(BT1, BT2, Out, IsLastLevel, AKVs, BKVs, Count, {0, FromPID}) ->
 
     receive
         {step, From, HowMany} ->
-            scan(BT1, BT2, Out, IsLastLevel, AKVs, BKVs, Count, {HowMany, From})
+            scan(BT1, BT2, Out, IsLastLevel, AKVs, BKVs, Count, {N+HowMany, From})
     after 10000 ->
             case ?LOCAL_WRITER of
                 true ->
-                    Args = {BT1, BT2, hanoi_writer:serialize(Out), IsLastLevel, AKVs, BKVs, Count},
+                    Args = {BT1, BT2, hanoi_writer:serialize(Out), IsLastLevel, AKVs, BKVs, Count, N},
                     Keep = zlib:gzip ( erlang:term_to_binary( Args ) ),
                     hibernate_scan(Keep);
                 false ->
@@ -137,8 +140,10 @@ scan(BT1, BT2, Out, IsLastLevel, [{Key1,Value1}|AT]=AKVs, [{Key2,Value2}|BT]=BKV
             end,
             scan(BT1, BT2, Out2, IsLastLevel, AKVs, BT, Count+1, step(Step));
 
+       %% cases below have Key1 == Key2, hence it consumes 2 elements
+
        (?TOMBSTONE =:= Value2) and (true =:= IsLastLevel) ->
-            scan(BT1, BT2, Out, IsLastLevel, AT, BT, Count, step(Step));
+            scan(BT1, BT2, Out, IsLastLevel, AT, BT, Count, step(Step, 2));
 
        true ->
             case ?LOCAL_WRITER of
@@ -147,13 +152,26 @@ scan(BT1, BT2, Out, IsLastLevel, [{Key1,Value1}|AT]=AKVs, [{Key2,Value2}|BT]=BKV
                 false ->
                     ok = hanoi_writer:add(Out2=Out, Key2, Value2)
             end,
-            scan(BT1, BT2, Out2, IsLastLevel, AT, BT, Count+1, step(Step))
+            scan(BT1, BT2, Out2, IsLastLevel, AT, BT, Count+1, step(Step, 2))
     end.
 
+scan_only(BT, Out, IsLastLevel, KVs, Count, {N, FromPID}) when N < 1, KVs =/= [] ->
+    case FromPID of
+        none ->
+            ok;
+        {PID, Ref} ->
+            PID ! {Ref, step_done}
+    end,
+
+    receive
+        {step, From, HowMany} ->
+            scan_only(BT, Out, IsLastLevel, KVs, Count, {N+HowMany, From})
+    end;
+
 scan_only(BT, Out, IsLastLevel, [], Count, {_, FromPID}=Step) ->
     case hanoi_reader:next_node(BT) of
         {node, KVs} ->
-            scan_only(BT, Out, IsLastLevel, KVs, Count, step(Step));
+            scan_only(BT, Out, IsLastLevel, KVs, Count, Step);
         end_of_data ->
             case FromPID of
                 none ->