Add bloom filter to btree index format

rebar.config

@@ -2,5 +2,6 @@
 {cover_enabled, true}. 
 
 {deps, [
-       {plain_fsm, "1.1.*", {git, "git://github.com/uwiger/plain_fsm", {branch, "master"}}}
+       {plain_fsm, "1.1.*", {git, "git://github.com/uwiger/plain_fsm", {branch, "master"}}},
+       {ebloom, "1.0.*", {git, "git://github.com/basho/ebloom.git", {branch, "master"}}}
 ]}.

src/fractal_btree_level.erl

@@ -269,7 +269,8 @@ begin_merge(State) ->
     Owner = self(),
 
     spawn_link(fun() ->
-                       {ok, OutCount} = fractal_btree_merger:merge(AFileName, BFileName, XFileName),
+                       {ok, OutCount} = fractal_btree_merger:merge(AFileName, BFileName, XFileName,
+                                                                   State#state.level * 2),
                        Owner ! {merge_done, OutCount, XFileName}
                end),
 

src/fractal_btree_merger.erl

@@ -4,12 +4,12 @@
 %% Naive Merge of two b-trees.  A better implementation should iterate leafs, not KV's
 %%
 
--export([merge/3]).
+-export([merge/4]).
 
 -record(state, { out, a_pid, b_pid }).
 
-merge(A,B,C) ->
-    {ok, Out} = fractal_btree_writer:open(C),
+merge(A,B,C, Size) ->
+    {ok, Out} = fractal_btree_writer:open(C, Size),
     Owner = self(),
     PID1 = spawn_link(fun() -> scan(Owner, A) end),
     PID2 = spawn_link(fun() -> scan(Owner, B) end),

src/fractal_btree_reader.erl

@@ -5,7 +5,7 @@
 -export([open/1,close/1,lookup/2,fold/3]).
 
 -record(node, { level, members=[] }).
--record(index, {file, root}).
+-record(index, {file, root, bloom}).
 
 open(Name) ->
 
@@ -14,11 +14,15 @@ open(Name) ->
 
     %% read root position
     {ok, <<RootPos:64/unsigned>>} = file:pread(File, FileInfo#file_info.size-8, 8),
+    {ok, <<BloomSize:32/unsigned>>} = file:pread(File, FileInfo#file_info.size-12, 4),
+    {ok, BloomData} = file:pread(File, FileInfo#file_info.size-12-BloomSize ,BloomSize),
+
+    {ok, Bloom} = ebloom:deserialize(BloomData),
 
     %% suck in the root
     {ok, Root} = read_node(File, RootPos),
 
-    {ok, #index{file=File, root=Root}}.
+    {ok, #index{file=File, root=Root, bloom=Bloom}}.
 
 
 fold(Fun, Acc0, #index{file=File}) ->
@@ -43,8 +47,13 @@ close(#index{file=File}) ->
     file:close(File).
 
 
-lookup(#index{file=File, root=Node},Key) ->
-    lookup_in_node(File,Node,Key).
+lookup(#index{file=File, root=Node, bloom=Bloom}, Key) ->
+    case ebloom:contains(Bloom, Key) of
+        true ->
+            lookup_in_node(File,Node,Key);
+        false ->
+            notfound
+    end.
 
 lookup_in_node(_File,#node{level=0,members=Members},Key) ->
     case lists:keyfind(Key,1,Members) of

src/fractal_btree_writer.erl

@@ -1,6 +1,11 @@
-
 -module(fractal_btree_writer).
 
+%%
+%% Streaming btree writer. Accepts only monotonically increasing keys for put.
+%%
+
+%% TODO: add a bloom filter to the file
+
 -define(NODE_SIZE, 2*1024).
 
 -behavior(gen_server).
@@ -9,7 +14,7 @@
 -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
 	 terminate/2, code_change/3]).
 
--export([open/1, add/3,close/1]).
+-export([open/1, open/2, add/3,close/1]).
 
 -record(node, { level, members=[], size=0 }).
 
@@ -20,14 +25,20 @@
 
                  nodes = [] :: [ #node{} ],
 
-                 name :: string()
+                 name :: string(),
+
+                 bloom
                }).
 
 
 %%% PUBLIC API
 
+open(Name,Size) ->
+    gen_server:start(?MODULE, [Name,Size], []).
+
+
 open(Name) ->
-    gen_server:start(?MODULE, [Name], []).
+    gen_server:start(?MODULE, [Name,2048], []).
 
 
 add(Ref,Key,Data) ->
@@ -39,15 +50,16 @@ close(Ref) ->
 %%%
 
 
-init([Name]) ->
+init([Name,Size]) ->
 
 %    io:format("got name: ~p~n", [Name]),
 
     {ok, IdxFile} = file:open( fractal_btree_util:index_file_name(Name),
                                [raw, exclusive, write, delayed_write]),
-
+    {ok, BloomFilter} = ebloom:new(Size, 0.01, 123),
     {ok, #state{ name=Name,
-                 index_file_pos=0, index_file=IdxFile
+                 index_file_pos=0, index_file=IdxFile,
+                 bloom = BloomFilter
                }}.
 
 handle_cast({add, Key, Data}, State) when is_binary(Key), is_binary(Data) ->
@@ -79,9 +91,12 @@ code_change(_OldVsn, State, _Extra) ->
 
 
 
-flush_nodes(#state{ nodes=[], last_node_pos=LastNodePos }=State) ->
+flush_nodes(#state{ nodes=[], last_node_pos=LastNodePos, bloom=Ref }=State) ->
 
-    Trailer = << 0:8, LastNodePos:64/unsigned >>,
+    Bloom = ebloom:serialize(Ref),
+    BloomSize = byte_size(Bloom),
+
+    Trailer = << 0:32, Bloom/binary, BloomSize:32/unsigned, LastNodePos:64/unsigned >>,
     IdxFile = State#state.index_file,
 
     ok = file:write(IdxFile, Trailer),
@@ -112,6 +127,8 @@ add_record(Level, Key, Value, #state{ nodes=[ #node{level=Level, members=List, s
 
     NewSize = NodeSize + fractal_btree_util:estimate_node_size_increment(List, Key, Value),
 
+    ebloom:insert( State#state.bloom, Key ),
+
     NodeMembers = [{Key,Value} | List],
     if
        NewSize >= ?NODE_SIZE ->

test/fractal_btree_tests.erl

@@ -83,7 +83,7 @@ merge_test() ->
     ok = fractal_btree_writer:close(BT2),
 
 
-    {Time,{ok,Count}} = timer:tc(fractal_btree_merger, merge, ["test1", "test2", "test3"]),
+    {Time,{ok,Count}} = timer:tc(fractal_btree_merger, merge, ["test1", "test2", "test3", 8]),
 
     error_logger:info_msg("time to merge: ~p/sec (time=~p, count=~p)~n", [1000000/(Time/Count), Time/1000000, Count]),