修复批量插入段错误，支持从库查询

lua-mongo.c

@@ -499,7 +499,7 @@ op_insert(lua_State *L) {
 		int i;
 		for (i=1;i<=s;i++) {
 			lua_rawgeti(L,3,i);
-			document doc = lua_touserdata(L,3);
+			document doc = lua_touserdata(L,-1);
 			lua_pop(L,1);	// must call lua_pop before luaL_addlstring, because addlstring may change stack top
 			luaL_addlstring(&b, (const char *)doc, get_length(doc));
 		}

mongo.lua

@@ -194,6 +194,21 @@ function mongo_collection:findOne(query, selector)
 	return bson_decode(doc)
 end
 
+function mongo_collection:findOneSecondary(query, selector)
+	local request_id = self.connection:genId()
+	local sock = self.connection.__sock
+	local pack = driver.query(request_id, 4, self.full_name, 0, 1,
+		query and bson_encode(query) or empty_bson, selector and bson_encode(selector))
+
+	-- todo: check send
+	socket.write(sock, pack)
+
+	local _, _, reply_id, doc = get_reply(sock)
+	assert(request_id == reply_id, "Reply from mongod error")
+	-- todo: check succ
+	return bson_decode(doc)
+end
+
 function mongo_collection:find(query, selector)
 	return setmetatable( {
 		__collection = self,
@@ -207,6 +222,19 @@ function mongo_collection:find(query, selector)
 	} , cursor_meta)
 end
 
+function mongo_collection:findSecondary(query, selector)
+	return setmetatable( {
+		__collection = self,
+		__query = query and bson_encode(query) or empty_bson,
+		__selector = selector and bson_encode(selector),
+		__ptr = nil,
+		__data = nil,
+		__cursor = nil,
+		__document = {},
+		__flags = 4,
+	} , cursor_meta)
+end
+
 function mongo_cursor:hasNext()
 	if self.__ptr == nil then
 		if self.__document == nil then