diff --git a/src/common/string_util.erl b/src/common/string_util.erl
index 7a599dd..8a8da0f 100644
--- a/src/common/string_util.erl
+++ b/src/common/string_util.erl
@@ -3,8 +3,33 @@
 %% Kevin Lynx
 %% 
 -module(string_util).
--export([format/2]).
+-compile(export_all).
+-export([format/2, strip_invalid_unicode/1]).
 
 format(Fmt, Arg) when is_list(Fmt), is_list(Arg) ->
 	lists:flatten(io_lib:format(Fmt, Arg)).
 	
+% strip these unicode control characters
+strip_invalid_unicode(L) when is_list(L) ->
+	binary_to_list(strip_invalid_unicode(list_to_binary(L)));
+strip_invalid_unicode(<<>>) ->
+	<<>>;
+strip_invalid_unicode(<<C/utf8, R/binary>>) ->
+	case is_valid_unicode(C) of
+		true ->
+			RR = strip_invalid_unicode(R),
+			<<C/utf8, RR/binary>>;
+		false ->
+			strip_invalid_unicode(R)
+	end;
+strip_invalid_unicode(<<_, R/binary>>) ->
+	strip_invalid_unicode(R).
+	
+is_valid_unicode(C) when C < 16#20 ->
+	false;
+is_valid_unicode(C) when C >= 16#7f, C =< 16#ff ->
+	false;
+is_valid_unicode(_) ->
+	true.
+
+
diff --git a/src/http_front/sphinx_search.erl b/src/http_front/sphinx_search.erl
index 9d9a41b..6b82b55 100644
--- a/src/http_front/sphinx_search.erl
+++ b/src/http_front/sphinx_search.erl
@@ -18,10 +18,9 @@ search(Conn, Key, Offset, Count) ->
     {T2, TDocs} = case catch giza_request:send(Q4) of
     	{'EXIT', R} ->
     		?W(?FMT("sphinx search error ~p", [R])),
-    		[];
+    		{now(), []};
     	{ok, Ret} ->
-    		T = now(),
-    		{T, decode_search_ret(Conn, Ret)}
+    		{now(), decode_search_ret(Conn, Ret)}
     end,
     T3 = now(),
     Stats = {timer:now_diff(T2, T1), timer:now_diff(T3, T2)},
diff --git a/src/sphinx_builder/sphinx_cmd.erl b/src/sphinx_builder/sphinx_cmd.erl
index 147c8f1..f7ee856 100644
--- a/src/sphinx_builder/sphinx_cmd.erl
+++ b/src/sphinx_builder/sphinx_cmd.erl
@@ -27,7 +27,8 @@ do_build_init_index(MainFile, DeltaFile, CfgFile) ->
 build_delta_index(IndexFile, Delta, CfgFile, MinID, MaxID) ->
 	Cmd = "indexer -c " ++ CfgFile ++ " --rotate " ++ Delta,
 	Res = os:cmd(Cmd),
-	Dest = backup_delta_file(Delta, MinID, MaxID, IndexFile),
+	Success = check_cmd_success(Res),
+	Dest = backup_delta_file(Delta, MinID, MaxID, IndexFile, Success),
 	?I(?FMT("command `~s' result on ~s~n" ++ Res, [Cmd, Dest])).
 
 merge_index(Main, Delta, CfgFile) ->
@@ -36,9 +37,13 @@ merge_index(Main, Delta, CfgFile) ->
 	Res = os:cmd(Cmd),
 	?I(?FMT("command `~s' result~n" ++ Res, [Cmd])).
 
-backup_delta_file(Delta, MinID, MaxID, IndexFile) ->
+backup_delta_file(Delta, MinID, MaxID, IndexFile, Flag) ->
 	Path = filename:dirname(IndexFile),
 	Dest = string_util:format(Path ++ "/" ++ Delta ++ "[~b-~b]" ++ ".xml",
 		[MinID, MaxID]),
-	file:copy(IndexFile, Dest),
+	if not Flag -> file:copy(IndexFile, Dest); true -> skip end,
 	Dest.
+
+% too simple
+check_cmd_success(Res) ->
+	string:str(Res, "succesfully") > 0.
diff --git a/src/sphinx_builder/sphinx_xml.erl b/src/sphinx_builder/sphinx_xml.erl
index a8f68ef..08db1b3 100644
--- a/src/sphinx_builder/sphinx_xml.erl
+++ b/src/sphinx_builder/sphinx_xml.erl
@@ -5,6 +5,7 @@
 %%
 -module(sphinx_xml).
 -behaviour(gen_server).
+-compile(export_all).
 -include("vlog.hrl").
 -export([init/1,
          handle_call/3,
@@ -48,9 +49,9 @@ handle_cast(save, #state{docs = Docs, ids = IDs} = State) when length(Docs) > 0
 handle_cast(stop, State) ->
 	{stop, normal, State}.
 
-handle_call({insert, {ID, Hash, Name, Files, Query, CreatedAt}}, _From, State) ->
+handle_call({insert, DocT}, _From, State) ->
 	#state{docs = Docs, ids = IDs, max = Max} = State,
-	Doc = sphinx_doc:element(Hash, Name, Files, ID, Query, CreatedAt),
+	{ID, Doc} = create_doc(DocT),
 	{NewDocs, NewIDs} = try_save([Doc|Docs], Max, [ID|IDs]),
 	{reply, ok, State#state{docs = NewDocs, ids = NewIDs}};
 
@@ -83,3 +84,20 @@ get_id_range([First|IDs]) ->
 	lists:foldl(fun(ID, {Min, Max}) ->
 		{min(ID, Min), max(ID, Max)}
 	end, {First, First}, IDs).
+
+create_doc({ID, Hash, Name, Files, Query, CreatedAt}) ->
+	ValidName = valid_name(Name),
+	ValidFiles = valid_file_names(Files),
+	Doc = sphinx_doc:element(Hash, ValidName, ValidFiles, ID, Query, CreatedAt),
+	{ID, Doc}.
+
+valid_file_names(Files) ->
+	[{valid_name(Name), Length} || {Name, Length} <- Files].
+
+valid_name(S) ->
+	ValidName = string_util:strip_invalid_unicode(S),
+	if length(ValidName) < length(S) ->
+		?I(?FMT("~s -> ~s", [S, ValidName]));
+		true -> ok
+	end,
+	ValidName.