Reworking shuffle_up to sate Matthias's passion for beautiful code

1 files changed, 17 insertions, 19 deletions

diff --git a/src/rabbit_disk_queue.erl b/src/rabbit_disk_queue.erl
index 63076eb914..e3b47e89dc 100644
--- a/src/rabbit_disk_queue.erl
+++ b/src/rabbit_disk_queue.erl
@@ -1069,30 +1069,28 @@ remove_gaps_in_sequences(#dqstate { sequences = Sequences }) ->
 		  ok = mnesia:write_lock_table(rabbit_disk_queue),
 		  lists:foreach(
 		    fun ({Q, ReadSeqId, WriteSeqId}) ->
-			    Gap = shuffle_up(Q, WriteSeqId - 1, WriteSeqId - ReadSeqId, 0),
+			    Gap = shuffle_up(Q, ReadSeqId - 1, WriteSeqId - 1, 0),
 			    true = ets:insert(Sequences, {Q, ReadSeqId + Gap, WriteSeqId})
 		    end, ets:match_object(Sequences, '_'))
 	  end).
 
-shuffle_up(_Q, _SeqId, 0, Gap) ->
+shuffle_up(_Q, SeqId, SeqId, Gap) ->
     Gap;
-shuffle_up(Q, SeqId, N, 0) ->
-    %% no gaps so far so don't need to rewrite
-    case mnesia:read(rabbit_disk_queue, {Q, SeqId}, write) of
-	[] -> shuffle_up(Q, SeqId - 1, N - 1, 1);
-	_ -> shuffle_up(Q, SeqId - 1, N - 1, 0)
-    end;
-shuffle_up(Q, SeqId, N, Gap) ->
-    %% have gaps, so whenever we find something, rewrite it higher up
-    case mnesia:read(rabbit_disk_queue, {Q, SeqId}, write) of
-	[] -> shuffle_up(Q, SeqId - 1, N - 1, Gap + 1);
-	[Obj = #dq_msg_loc { is_delivered = true }] ->
-	    mnesia:write(rabbit_disk_queue,
-			 Obj #dq_msg_loc { queue_and_seq_id = {Q, SeqId + Gap }},
-			 write),
-	    mnesia:delete(rabbit_disk_queue, {Q, SeqId}, write),
-	    shuffle_up(Q, SeqId - 1, N - 1, Gap)
-    end.
+shuffle_up(Q, BaseSeqId, SeqId, Gap) ->
+    GapInc =
+	case mnesia:read(rabbit_disk_queue, {Q, SeqId}, write) of
+	    [] -> 1;
+	    [Obj = #dq_msg_loc { is_delivered = IsDelivered }] when IsDelivered
+								    orelse (Gap =:= 0) ->
+		if Gap =:= 0 -> ok;
+		   true -> mnesia:write(rabbit_disk_queue,
+					Obj #dq_msg_loc { queue_and_seq_id = {Q, SeqId + Gap }},
+					write),
+			   mnesia:delete(rabbit_disk_queue, {Q, SeqId}, write)
+		end,
+		0
+	end,
+    shuffle_up(Q, BaseSeqId, SeqId - 1, Gap + GapInc).
 
 load_messages(undefined, [], State = #dqstate { file_summary = FileSummary,
 						current_file_name = CurName }) ->