More efficient term size calculation

Unlike byte_size(term_to_binary(Term)), the BIF erlang:external_size/1 doesn't
do the serialization step, it only calculates the maximum external size for
any term, which is more efficient (faster and avoids the garbage generation).

With the test couch_http_bulk_writes.sh at [1], using 20 writers and batches
of 100 1Kb documents, it's possible to write about 1 400 000 documents with
this patch instead of about 1 300 000.

[1] https://github.com/fdmanana/basho_bench_couch




git-svn-id: https://svn.apache.org/repos/asf/couchdb/trunk@1129597 13f79535-47bb-0310-9956-ffa450edef68

src/couchdb/couch_btree.erl

@@ -276,26 +276,26 @@ complete_root(Bt, KPs) ->
 % written. Plus with the "case byte_size(term_to_binary(InList)) of" code
 % it's probably really inefficient.
 
-chunkify(#btree{compression = Comp} = Bt, InList) ->
-    case byte_size(couch_compress:compress(InList, Comp)) of
+chunkify(InList) ->
+    case ?term_size(InList) of
     Size when Size > ?CHUNK_THRESHOLD ->
         NumberOfChunksLikely = ((Size div ?CHUNK_THRESHOLD) + 1),
         ChunkThreshold = Size div NumberOfChunksLikely,
-        chunkify(Bt, InList, ChunkThreshold, [], 0, []);
+        chunkify(InList, ChunkThreshold, [], 0, []);
     _Else ->
         [InList]
     end.
 
-chunkify(_Bt, [], _ChunkThreshold, [], 0, OutputChunks) ->
+chunkify([], _ChunkThreshold, [], 0, OutputChunks) ->
     lists:reverse(OutputChunks);
-chunkify(_Bt, [], _ChunkThreshold, OutList, _OutListSize, OutputChunks) ->
+chunkify([], _ChunkThreshold, OutList, _OutListSize, OutputChunks) ->
     lists:reverse([lists:reverse(OutList) | OutputChunks]);
-chunkify(Bt, [InElement | RestInList], ChunkThreshold, OutList, OutListSize, OutputChunks) ->
-    case byte_size(couch_compress:compress(InElement, Bt#btree.compression)) of
+chunkify([InElement | RestInList], ChunkThreshold, OutList, OutListSize, OutputChunks) ->
+    case ?term_size(InElement) of
     Size when (Size + OutListSize) > ChunkThreshold andalso OutList /= [] ->
-        chunkify(Bt, RestInList, ChunkThreshold, [], 0, [lists:reverse([InElement | OutList]) | OutputChunks]);
+        chunkify(RestInList, ChunkThreshold, [], 0, [lists:reverse([InElement | OutList]) | OutputChunks]);
     Size ->
-        chunkify(Bt, RestInList, ChunkThreshold, [InElement | OutList], OutListSize + Size, OutputChunks)
+        chunkify(RestInList, ChunkThreshold, [InElement | OutList], OutListSize + Size, OutputChunks)
     end.
 
 modify_node(Bt, RootPointerInfo, Actions, QueryOutput) ->
@@ -350,7 +350,7 @@ get_node(#btree{fd = Fd}, NodePos) ->
 
 write_node(#btree{fd = Fd, compression = Comp} = Bt, NodeType, NodeList) ->
     % split up nodes into smaller sizes
-    NodeListList = chunkify(Bt, NodeList),
+    NodeListList = chunkify(NodeList),
     % now write out each chunk and return the KeyPointer pairs for those nodes
     ResultList = [
         begin

src/couchdb/couch_db.hrl

@@ -27,6 +27,12 @@
 -define(b2l(V), binary_to_list(V)).
 -define(l2b(V), list_to_binary(V)).
 -define(term_to_bin(T), term_to_binary(T, [{minor_version, 1}])).
+-define(term_size(T),
+    try
+        erlang:external_size(T)
+    catch _:_ ->
+        byte_size(?term_to_bin(T))
+    end).
 
 -define(DEFAULT_ATTACHMENT_CONTENT_TYPE, <<"application/octet-stream">>).
 

src/couchdb/couch_db_updater.erl

@@ -888,7 +888,7 @@ copy_compact(Db, NewDb0, Retry) ->
     fun(#doc_info{high_seq=Seq}=DocInfo, _Offset,
         {AccNewDb, AccUncopied, AccUncopiedSize, AccCopiedSize, TotalCopied}) ->
 
-        AccUncopiedSize2 = AccUncopiedSize + byte_size(?term_to_bin(DocInfo)),
+        AccUncopiedSize2 = AccUncopiedSize + ?term_size(DocInfo),
         if AccUncopiedSize2 >= BufferSize ->
             NewDb2 = copy_docs(
                 Db, AccNewDb, lists:reverse([DocInfo | AccUncopied]), Retry),

src/couchdb/couch_view_compactor.erl

@@ -57,7 +57,7 @@ compact_group(Group, EmptyGroup) ->
             Msg = "Duplicates of ~s detected in ~s ~s - rebuild required",
             exit(io_lib:format(Msg, [DocId, DbName, GroupId]));
         true -> ok end,
-        AccSize2 = AccSize + byte_size(?term_to_bin(KV)),
+        AccSize2 = AccSize + ?term_size(KV),
         if AccSize2 >= BufferSize ->
             {ok, Bt2} = couch_btree:add(Bt, lists:reverse([KV|Acc])),
             couch_task_status:update("Copied ~p of ~p Ids (~p%)",
@@ -90,7 +90,7 @@ compact_view(View, EmptyView, BufferSize) ->
 
     %% Key is {Key,DocId}
     Fun = fun(KV, {Bt, Acc, AccSize, TotalCopied}) ->
-        AccSize2 = AccSize + byte_size(?term_to_bin(KV)),
+        AccSize2 = AccSize + ?term_size(KV),
         if AccSize2 >= BufferSize ->
             {ok, Bt2} = couch_btree:add(Bt, lists:reverse([KV|Acc])),
             couch_task_status:update("View #~p: copied ~p of ~p KVs (~p%)",

src/couchdb/couch_work_queue.erl

@@ -42,7 +42,7 @@ new(Options) ->
 queue(Wq, Item) when is_binary(Item) ->
     gen_server:call(Wq, {queue, Item, byte_size(Item)}, infinity);
 queue(Wq, Item) ->
-    gen_server:call(Wq, {queue, Item, byte_size(?term_to_bin(Item))}, infinity).
+    gen_server:call(Wq, {queue, Item, ?term_size(Item)}, infinity).
 
 
 dequeue(Wq) ->