diff --git a/Readme.md b/Readme.md
index 4eb694d..44d8825 100644
--- a/Readme.md
+++ b/Readme.md
@@ -234,10 +234,10 @@ Notes
 Known Issues
 ---------------------------
 1. Auth bson message has reduntant value.
-2. Could not inserting a null array, it always inserted as a document.
-3. Gridfs_new api only create a meta info in file_col.
+2. Gridfs_new api only create a meta info in file_col.
 
-Example
+
+Basic Usage
 ---------------------------
             local mongo = require "resty.mongol"
             conn = mongo:new()
@@ -252,7 +252,11 @@ Example
 
             r = col:find_one({name="dog"})
             ngx.say(r["name"])
+			
+
+See wiki for advanced examples
 
+ 
 For Test Case
 --------------------
 #####mongo config:
diff --git a/lib/resty/mongol/ObjectId.lua b/lib/resty/mongol/ObjectId.lua
new file mode 100755
index 0000000..5ee744d
--- /dev/null
+++ b/lib/resty/mongol/ObjectId.lua
@@ -0,0 +1,104 @@
+local type = type
+local require = require
+local assert = assert
+local setmetatable = setmetatable
+
+local string_byte = string.byte
+local string_format = string.format
+local table_insert = table.insert
+local table_concat = table.concat
+local os_time = os.time
+local io_popen = io.popen
+
+local hasposix, posix = pcall(require , "posix")
+
+local ngx = ngx
+local ngx_decode_base64 = ngx.decode_base64
+local ngx_encode_base64 = ngx.encode_base64
+local ngx_md5_bin = ngx.md5_bin
+
+module(...)
+
+local ll = require(_PACKAGE.."ll")
+local num_to_le_uint = ll.num_to_le_uint
+local num_to_be_uint = ll.num_to_be_uint
+local be_uint_tonum = ll.be_uint_to_num
+
+local machineid
+local function _get_os_machineid()
+  if hasposix then
+    machineid = posix.uname("%n")
+  else
+    machineid = assert(io_popen("uname -n")):read("*l")
+  end
+  machineid = ngx_md5_bin(machineid):sub(1, 3)
+  return machineid
+end
+
+local pid
+local function _get_os_pid()
+  pid = num_to_le_uint(ngx.var.pid, 2)
+  return pid 
+end
+
+local inc = 0
+local function _generate_id()
+  inc = inc + 1
+  -- "A BSON ObjectID is a 12-byte value consisting of a 4-byte timestamp (seconds since epoch), a 3-byte machine id, a 2-byte process id, and a 3-byte counter. Note that the timestamp and counter fields must be stored big endian unlike the rest of BSON"
+  return num_to_be_uint(os_time(), 4) .. (machineid or _get_os_machineid()) .. (pid or _get_os_pid()) .. num_to_be_uint(inc, 3)
+end
+
+local function _new(cls, id) 
+  if id then
+    if type(id) == 'string' then
+      local len = #id
+      if len == 12 then
+      elseif len == 16 then
+        id = ngx_decode_base64((id:gsub('!', '+'):gsub('_', '/')))
+      else
+        return nil, 'expecting string is 12 or 16 length'
+      end
+    else
+      return nil, 'expecting id is string or nil'
+    end
+  end
+  local o = { id = id or _generate_id() }
+  setmetatable(o, cls)
+  return o
+end
+
+setmetatable(_M, { __call = _new })
+
+__index = _M
+
+__tostring = function(ob)
+  return ngx_encode_base64(ob.id):gsub('%+', '!'):gsub('/', '_')
+end
+
+__tojson = __tostring
+
+__eq = function (a, b)
+  return a.id == b.id
+end
+
+tostring = __tostring
+
+function get_ts(ob)
+  return be_uint_to_num(ob.id, 1, 4)
+end
+
+function get_pid(ob)
+  return be_uint_to_num(ob.id, 8, 9)
+end
+
+function get_hostname(ob)
+  local t = {}
+  for i = 5, 7 do
+    table_insert(t, string_format("%02x", string_byte(ob.id, i, i))) 
+  end
+  return table_concat(t)
+end
+
+function get_inc(ob)
+  return be_uint_to_num(ob.id, 10, 12)
+end
diff --git a/lib/resty/mongol/bson-lua/bson.lua b/lib/resty/mongol/bson-lua/bson.lua
deleted file mode 100644
index d92e6d8..0000000
--- a/lib/resty/mongol/bson-lua/bson.lua
+++ /dev/null
@@ -1,220 +0,0 @@
---
--- Pure Lua (5.1) implementation of BSON
---
---
--- Copyright (c) 2013, Todd Coram. All rights reserved.
--- See LICENSE for details.
---
-
-local bson = {}
-
--- Helper functions
-
-local function toLSB(bytes,value)
-  local res = ''
-  local size = bytes
-  local str = ""
-  for j=1,size do
-     str = str .. string.char(value % 256)
-     value = math.floor(value / 256)
-  end
-  return str
-end
-
-local function toLSB32(value) return toLSB(4,value) end
-local function toLSB64(value) return toLSB(8,value) end
-
-local function fromLSB32(s)
-   return s:byte(1) + (s:byte(2)*256) + 
-      (s:byte(3)*65536) + (s:byte(4)*16777216)
-end
-
-local function fromLSB64(s)
-   return fromLSB32(s) +
-      (s:byte(5)*4294967296) + (s:byte(6)*1099511627776) +
-      (s:byte(7)*2.8147497671066e+14) + (s:byte(8)*7.2057594037928e+16)
-end
-
-
--- BSON generators
---
-
-function bson.to_bool(n,v) 
-   local pre = "\008"..n.."\000"
-   if v then
-      return pre.."\001"
-   else
-      return pre.."\000"
-   end
-end
-
-function bson.to_str(n,v) return "\002"..n.."\000"..toLSB32(#v+1)..v.."\000" end
-function bson.to_int32(n,v) return "\016"..n.."\000"..toLSB32(v) end
-function bson.to_int64(n,v) return "\018"..n.."\000"..toLSB64(v) end
-function bson.to_x(n,v) return v(n) end
-
-function bson.utc_datetime(t)
-   local t = t or (os.time()*1000)
-   f = function (n)
-      return "\009"..n.."\000"..toLSB64(t)
-   end
-   return f
-end
-
--- Binary subtypes
-bson.B_GENERIC  = "\000"
-bson.B_FUNCTION = "\001"
-bson.B_UUID     = "\004"
-bson.B_MD5      = "\005"
-bson.B_USER_DEFINED = "\128"
-
-function bson.binary(v, subtype)
-   local subtype = subtype or bson.B_GENERIC
-   f = function (n) 
-      return "\005"..n.."\000"..toLSB32(#v)..subtype..v
-   end
-   return f
-end
-
-function bson.to_num(n,v)
-   if math.floor(v) ~= v then
-      return bson.to_double(n,v)
-   elseif v > 2147483647 or v < -2147483648 then
-      return bson.to_int64(n,v)
-   else
-      return bson.to_int32(n,v)
-   end
-end
-
-function bson.to_doc(n,doc)
-   local d=bson.start()
-   local doctype = "\003"
-   for cnt,v in ipairs(doc) do
-      local t = type(v)
-      local o = lua_to_bson_tbl[t](tostring(cnt-1),v)
-      d = d..o
-      doctype = "\004"
-   end
-   -- do this only if we don't have an array (enumerated pairs)
-   if d == "" then
-      for nm,v in pairs(doc) do
-	 local t = type(v)
-	 local o = lua_to_bson_tbl[t](nm,v)
-	 d = d..o
-      end
-   end
-   return doctype..n.."\000"..bson.finish(d)
-end
-
-
--- Mappings between lua and BSON.
--- "function" is a special catchall for non-direct mappings.
---
-lua_to_bson_tbl= {
-   boolean = bson.to_bool,
-   string = bson.to_str,
-   number = bson.to_num,
-   table = bson.to_doc,
-   ["function"] = bson.to_x
-}
-
--- BSON document creation.
---
-function bson.start() return "" end
-
-function bson.finish(doc) 
-   doc = doc .. "\000"
-   return toLSB32(#doc+4)..doc
-end
-
-function bson.encode(doc)
-   local d=bson.start()
-   for e,v in pairs(doc) do
-      local t = type(v)
-      local o = lua_to_bson_tbl[t](e,v)
-      d = d..o
-   end
-   return bson.finish(d)
-end
-
-
--- BSON parsers
-
-function bson.from_bool(s)
-   return s:byte(1) == 1, s:sub(2)
-end
-
-function bson.from_int32(s)
-   return fromLSB32(s:sub(1,4)), s:sub(5)
-end
-
-function bson.from_int64(s)
-   return fromLSB64(s:sub(1,8)), s:sub(9)
-end
-
-function bson.from_utc_date_time(s)
-   return fromLSB64(s:sub(1,8)), s:sub(9)
-end
-
-function bson.from_binary(s)
-   local len = fromLSB32(s:sub(1,4))
-   s = s:sub(6)
-   local str = s:sub(1,len-1)
-   return str, s:sub(len+1)
-end
-
-
-function bson.from_str(s)
-   local len = fromLSB32(s:sub(1,4))
-   s = s:sub(5)
-   local str = s:sub(1,len-1)
-   return str, s:sub(len+1)
-end
-
-
-function bson.decode_doc(doc,doctype)
-   local luatab = {}
-   local len = fromLSB32(doc:sub(1,4))
-   doc=doc:sub(5)
-   repeat
-      local val
-      local etype = doc:byte(1)
-      if etype == 0 then doc=doc:sub(2) break end
-      local ename = doc:match("(%Z+)\000",2)
-      doc = doc:sub(#ename+3)
-      val,doc = bson_to_lua_tbl[etype](doc,etype)
-      if doctype == 4 then
-	 table.insert(luatab,val)
-      else
-	 luatab[ename] = val
-      end
-   until not doc
-   return luatab,doc
-end
-
-bson_to_lua_tbl= {
-   [2] = bson.from_str,
-   [16] = bson.from_int32,
-   [18] = bson.from_int64,
-   [8] = bson.from_bool,
-   [3] = bson.decode_doc,
-   [4] = bson.decode_doc,
-   [5] = bson.from_binary,
-   [9] = bson.from_utc_date_time
-}
-
-function bson.decode(doc)
-   a,d=bson.decode_doc(doc,nil)
-   return a,d
-end
-
-function bson.decode_next_io(fd)
-   local slen = fd:read(4)
-   if not slen then return nil end
-   local len = fromLSB32(slen) - 4
-   local doc = fd:read(len)
-   return bson.decode(slen..doc)
-end
-
-
-return bson
diff --git a/lib/resty/mongol/bson.lua b/lib/resty/mongol/bson.lua
index 68a5577..6e590a0 100755
--- a/lib/resty/mongol/bson.lua
+++ b/lib/resty/mongol/bson.lua
@@ -7,10 +7,13 @@ local type = type
 local tonumber , tostring = tonumber , tostring
 local t_insert = table.insert
 local t_concat = table.concat
+local t_maxn = table.maxn
 local strformat = string.format
 local strmatch = string.match
 local strbyte = string.byte
 
+local Array = Array
+
 local ll = require ( mod_name .. ".ll" )
 local le_uint_to_num = ll.le_uint_to_num
 local le_int_to_num = ll.le_int_to_num
@@ -19,114 +22,176 @@ local num_to_le_int = ll.num_to_le_int
 local from_double = ll.from_double
 local to_double = ll.to_double
 
-local getlib = require ( mod_name .. ".get" )
+local getlib = require(mod_name..".get")
 local read_terminated_string = getlib.read_terminated_string
 
-local obid = require ( mod_name .. ".object_id" )
-local nbson = require ( mod_name .. ".bson-lua.bson" )
-local new_object_id = obid.new
-local object_id_mt = obid.metatable
+local ObjectId = require(mod_name..".ObjectId")
 local binary_mt = {}
 local utc_date = {}
 
-
-local function read_document ( get , numerical )
-	local bytes = le_uint_to_num ( get ( 4 ) )
-
-	local ho , hk , hv = false , false , false
-	local t = { }
-	while true do
-		local op = get ( 1 )
-		if op == "\0" then break end
-
-		local e_name = read_terminated_string ( get )
-		local v
-		if op == "\1" then -- Double
-			v = from_double ( get ( 8 ) )
-		elseif op == "\2" then -- String
-			local len = le_uint_to_num ( get ( 4 ) )
-			v = get ( len - 1 )
-			assert ( get ( 1 ) == "\0" )
-		elseif op == "\3" then -- Embedded document
-			v = read_document ( get , false )
-		elseif op == "\4" then -- Array
-			v = read_document ( get , true )
-		elseif op == "\5" then -- Binary
-			local len = le_uint_to_num ( get ( 4 ) )
-			local subtype = get ( 1 )
-			v = get ( len )
-		elseif op == "\7" then -- ObjectId
-			v = new_object_id ( get ( 12 ) )
-		elseif op == "\8" then -- false
-			local f = get ( 1 )
-			if f == "\0" then
-				v = false
-			elseif f == "\1" then
-				v = true
-			else
-				error ( f:byte ( ) )
-			end
-		elseif op == "\9" then -- UTC datetime milliseconds
-			v = le_uint_to_num ( get ( 8 ) , 1 , 8 )
-		elseif op == "\10" then -- Null
-			v = nil
-		elseif op == "\16" then --int32
-			v = le_int_to_num ( get ( 4 ) , 1 , 8 )
-        elseif op == "\17" then --int64
-            v = le_int_to_num(get(8), 1, 8)
-        elseif op == "\18" then --int64
-            v = le_int_to_num(get(8), 1, 8)
-		else
-			error ( "Unknown BSON type: " .. strbyte ( op ) )
-		end
-
-		if numerical then
-			t [ tonumber ( e_name ) ] = v
-		else
-			t [ e_name ] = v
-		end
-
-		-- Check for special universal map
-		if e_name == "_keys" then
-			hk = v
-		elseif e_name == "_vals" then
-			hv = v
-		else
-			ho = true
-		end
-	end
-
-	if not ho and hk and hv then
-		t = { }
-			for i=1,#hk do
-			t [ hk [ i ] ] = hv [ i ]
-		end
-	end
-
-	return t
+local function read_document(get, numerical)
+  local bytes = le_uint_to_num(get(4))
+
+  local t = {}
+  while true do
+    local op = get(1)
+    if op == "\0" then break end
+
+    local e_name = read_terminated_string(get)
+    local v
+    if op == "\1" then -- Double
+      v = from_double(get(8))
+    elseif op == "\2" then -- String
+      local len = le_uint_to_num(get(4))
+      v = get(len - 1)
+      assert(get(1) == "\0")
+    elseif op == "\3" then -- Embedded document
+      v = read_document(get, false)
+    elseif op == "\4" then -- Array
+      v = read_document(get, true)
+      if Array then
+        v = Array(v)
+      end
+    elseif op == "\5" then -- Binary
+      local len = le_uint_to_num(get(4))
+      local subtype = get(1)
+      v = get(len)
+    elseif op == "\7" then -- ObjectId
+      v = ObjectId(get(12))
+    elseif op == "\8" then -- false
+      local f = get(1)
+      if f == "\0" then
+        v = false
+      elseif f == "\1" then
+        v = true
+      else
+        error(f:byte())
+      end
+    elseif op == "\9" then -- UTC datetime milliseconds
+      v = le_uint_to_num(get(8), 1, 8)
+    elseif op == "\10" then -- Null
+      v = nil
+    elseif op == "\16" then --int32
+      v = le_int_to_num(get(4), 1, 8)
+    elseif op == "\17" then --int64 // timestamp
+      v = le_int_to_num(get(8), 1, 8)
+    elseif op == "\18" then --int64
+      v = le_int_to_num(get(8), 1, 8)
+    else
+      error ( "Unknown BSON type: " .. strbyte(op))
+    end
+
+    if numerical then
+      t[tonumber(e_name) + 1] = v
+    else
+      t[e_name] = v
+    end
+  end
+  return t
 end
 
 local function get_utc_date(v)
-    return setmetatable({v = v}, utc_date)
+  return setmetatable({v = v}, utc_date)
 end
 
 local function get_bin_data(v)
-    return setmetatable({v = v, st = "\0"}, binary_mt)
+  return setmetatable({v = v, st = "\0"}, binary_mt)
 end
 
-local function from_bson ( get )
-	local t = read_document ( get , false )
-	return t
+local function from_bson(get)
+  return read_document(get, false)
 end
 
 local to_bson
+local function pack(k, v)
+  local ot = type(v)
+  local mt = getmetatable(v)
+
+  if ot == "number" then
+    if math.floor(v) ~= v then
+      return "\1" .. k .. "\0" .. to_double ( v )
+    elseif v > 2147483647 or v < -2147483648 then -- 64bit
+      return "\18" .. k .. "\0" .. num_to_le_int ( v , 8 )
+    else -- 32bit
+      return "\16" .. k .. "\0" .. num_to_le_int ( v , 4 )
+    end
+  elseif ot == "nil" then
+    return "\10" .. k .. "\0"
+  elseif ot == "userdata" then
+    return "\10" .. k .. "\0"
+  elseif ot == "string" then
+    return "\2" .. k .. "\0" .. num_to_le_uint ( #v + 1 ) .. v .. "\0"
+  elseif ot == "boolean" then
+    if v == false then
+      return "\8" .. k .. "\0\0"
+    else
+      return "\8" .. k .. "\0\1"
+    end
+  elseif mt == ObjectId then
+    return "\7" .. k .. "\0" .. v.id
+  elseif mt == utc_date then
+    return "\9" .. k .. "\0" .. num_to_le_int(v.v, 8)
+  elseif mt == binary_mt then
+    return "\5" .. k .. "\0" .. num_to_le_uint(string.len(v.v)) .. 
+    v.st .. v.v
+  elseif ot == "table" then
+    local doc , array = to_bson(v)
+    if array then
+      return "\4" .. k .. "\0" .. doc
+    else
+      return "\3" .. k .. "\0" .. doc
+    end
+  else
+    error ( "Failure converting " .. ot ..": " .. tostring ( v ) )
+  end
+end
+
 function to_bson(ob)
-	return nbson.encode(ob)
+  -- Find out if ob if an array; or a table
+  local is_array = true
+  local max = 0
+  if Array then
+    if getmetatable(ob) == Array then
+      max = t_maxn(ob)
+    else
+      is_array = false
+    end
+  else
+    for k, v in pairs(ob) do
+      local t_k = type(k)
+      if is_array then
+        if t_k == "number" and k >= 1 then
+          if k >= max then
+            max = k
+          end
+        else
+          is_array = false
+        end
+      end
+      if not is_array then break end
+    end
+  end
+
+  local m
+  if is_array then
+    local r = {}
+    for i = 1, max do
+      r[i] = pack(i - 1, ob[i])
+    end
+    m = t_concat(r, "", 1, max)
+  else
+    local r = {}
+    for k, v in pairs(ob) do
+      t_insert(r, pack(tostring(k), v))
+    end
+    m = t_concat(r)
+  end
+  return num_to_le_uint(#m + 4 + 1 )..m.."\0", is_array
 end
 
 return {
-	from_bson = from_bson ;
-	to_bson = to_bson ;
-    get_bin_data = get_bin_data;
-    get_utc_date = get_utc_date;
+  from_bson = from_bson;
+  to_bson = to_bson;
+  get_bin_data = get_bin_data;
+  get_utc_date = get_utc_date;
 }
diff --git a/lib/resty/mongol/colmt.lua b/lib/resty/mongol/colmt.lua
index e09ba36..187485c 100755
--- a/lib/resty/mongol/colmt.lua
+++ b/lib/resty/mongol/colmt.lua
@@ -93,7 +93,7 @@ local function handle_reply ( conn , req_id , offset_i )
 
     local r = { }
     for i = 1 , t.numberReturned do
-	r[i] = from_bson(get)
+        r[i] = from_bson(get)
     end
 
     return cursorid, r, t
diff --git a/lib/resty/mongol/gridfs.lua b/lib/resty/mongol/gridfs.lua
index ff8eb07..2725134 100644
--- a/lib/resty/mongol/gridfs.lua
+++ b/lib/resty/mongol/gridfs.lua
@@ -1,10 +1,10 @@
-local mod_name = (...):match ( "^(.*)%..-$" )
+local mod_name = (...):match( "^(.*)%..-$" )
 
 local md5 = require "resty.md5"
 local str = require "resty.string"
-local bson = require ( mod_name .. ".bson" )
-local object_id = require ( mod_name .. ".object_id" )
-local gridfs_file= require ( mod_name .. ".gridfs_file" )
+local bson = require(mod_name..".bson")
+local ObjectId = require(mod_name..".ObjectId")
+local gridfs_file= require(mod_name..".gridfs_file")
 
 local gridfs_mt = { }
 local gridfs = { __index = gridfs_mt }
@@ -57,7 +57,7 @@ end
 
 function gridfs_mt:new(meta)
     meta = meta or {}
-    meta._id = meta._id or object_id.new()
+    meta._id = meta._id or ObjectId()
     meta.chunkSize = meta.chunkSize or 256*1024
     meta.filename = meta.filename or meta._id:tostring()
 
@@ -81,7 +81,7 @@ end
 function gridfs_mt:insert(fh, meta, safe)
     meta = meta or {}
     meta.chunkSize = meta.chunkSize or 256*1024
-    meta._id = meta._id or object_id.new()
+    meta._id = meta._id or ObjectId()
     meta.filename = meta.filename or meta._id:tostring()
 
     local n = 0
diff --git a/lib/resty/mongol/gridfs_file.lua b/lib/resty/mongol/gridfs_file.lua
index 4a99e16..4e09ecd 100644
--- a/lib/resty/mongol/gridfs_file.lua
+++ b/lib/resty/mongol/gridfs_file.lua
@@ -1,8 +1,8 @@
-local mod_name = (...):match ( "^(.*)%..-$" )
+local mod_name = (...):match( "^(.*)%..-$" )
 
 local md5 = require "resty.md5"
 local str = require "resty.string"
-local bson = require ( mod_name .. ".bson" )
+local bson = require(mod_name..".bson")
 
 local gridfs_file_mt = { }
 local gridfs_file = { __index = gridfs_file_mt }
@@ -129,6 +129,8 @@ function gridfs_file_mt:write(buf, offset, size)
         r,err = self.file_col:update({_id = self.files_id},nv, 
                         0, 0, true)
         if not r then return nil,"write failed: "..err end
+
+        self.file_size = nf
     end
 
     nv["$set"] = {md5 = 0}
diff --git a/lib/resty/mongol/ll.lua b/lib/resty/mongol/ll.lua
index ec06645..49312c9 100644
--- a/lib/resty/mongol/ll.lua
+++ b/lib/resty/mongol/ll.lua
@@ -31,7 +31,6 @@ local num_to_le_uint = function ( n , bytes )
 	for i=1 , bytes do
 		b [ i ] , n = n % 2^8 , floor ( n / 2^8 )
 	end
-	assert ( n == 0 )
 	return strchar ( unpack ( b ) )
 end
 local num_to_le_int = function ( n , bytes )
@@ -57,7 +56,6 @@ local num_to_be_uint = function ( n , bytes )
 	for i=bytes , 1 , -1 do
 		b [ i ] , n = n % 2^8 , floor ( n / 2^8 )
 	end
-	assert ( n == 0 )
 	return strchar ( unpack ( b ) )
 end
 
diff --git a/lib/resty/mongol/misc.lua b/lib/resty/mongol/misc.lua
index e676843..812e9d5 100755
--- a/lib/resty/mongol/misc.lua
+++ b/lib/resty/mongol/misc.lua
@@ -1,12 +1,11 @@
-local mod_name = (...):match ( "^(.*)%..-$" )
+local mod_name = (...):match("^(.*)%..-$")
 
-local ll = require ( mod_name .. ".ll" )
+local ll = require(mod_name..".ll")
 local num_to_le_uint = ll.num_to_le_uint
 local num_to_le_int = ll.num_to_le_int
 local le_uint_to_num = ll.le_uint_to_num
 local le_bpeek = ll.le_bpeek
 
-
 local getmetatable , setmetatable = getmetatable , setmetatable
 local pairs = pairs
 local next = next
diff --git a/lib/resty/mongol/object_id.lua b/lib/resty/mongol/object_id.lua
deleted file mode 100755
index fc3f2bb..0000000
--- a/lib/resty/mongol/object_id.lua
+++ /dev/null
@@ -1,83 +0,0 @@
-local mod_name = (...):match ( "^(.*)%..-$" )
-
-local setmetatable = setmetatable
-local strbyte = string.byte
-local strformat = string.format
-local t_insert = table.insert
-local t_concat = table.concat
-
-local hasposix , posix = pcall ( require , "posix" )
-
-local ll = require ( mod_name .. ".ll" )
-local num_to_le_uint = ll.num_to_le_uint
-local num_to_be_uint = ll.num_to_be_uint
-
-local function _tostring(ob)
-    local t = {}
-    for i = 1 , 12 do
-        t_insert(t, strformat("%02x", strbyte(ob.id, i, i))) 
-    end
-    return t_concat(t)
-end
-
-local function _get_ts(ob)
-    return ll.be_uint_to_num(ob.id, 1, 4)
-end
-
-local function _get_hostname(ob)
-    local t = {}
-    for i = 5, 7 do
-        t_insert(t, strformat("%02x", strbyte(ob.id, i, i))) 
-    end
-    return t_concat(t)
-end
-
-local function _get_pid(ob)
-    return ll.be_uint_to_num(ob.id, 8, 9)
-end
-
-local function _get_inc(ob)
-    return ll.be_uint_to_num(ob.id, 10, 12)
-end
-
-local object_id_mt = {
-    __tostring = _tostring;
-    __eq = function ( a , b ) return a.id == b.id end ;
-}
-
-local machineid
-if hasposix then
-    machineid = posix.uname("%n")
-else
-    machineid = assert(io.popen("uname -n")):read("*l")
-end
-machineid = ngx.md5_bin(machineid):sub(1, 3)
-
-local pid = num_to_le_uint(ngx.var.pid, 2)
-
-local inc = 0
-local function generate_id ( )
-    inc = inc + 1
-    -- "A BSON ObjectID is a 12-byte value consisting of a 4-byte timestamp (seconds since epoch), a 3-byte machine id, a 2-byte process id, and a 3-byte counter. Note that the timestamp and counter fields must be stored big endian unlike the rest of BSON"
-    return num_to_be_uint ( os.time ( ) , 4 ) .. machineid .. pid .. num_to_be_uint ( inc , 3 )
-end
-
-local function new_object_id(str)
-    if str then
-        assert(#str == 12)
-    else
-        str = generate_id()
-    end
-    return setmetatable({id = str,
-                        tostring = _tostring,
-                        get_ts = _get_ts,
-                        get_pid = _get_pid,
-                        get_hostname = _get_hostname,
-                        get_inc = _get_inc,
-                        } , object_id_mt)
-end
-
-return {
-    new = new_object_id ;
-    metatable = object_id_mt ;
-}
diff --git a/t/cluster.t b/t/cluster.t
new file mode 100644
index 0000000..9415203
--- /dev/null
+++ b/t/cluster.t
@@ -0,0 +1,190 @@
+# vim:set ft= ts=4 sw=4 et:
+
+use Test::Nginx::Socket;
+use Cwd qw(cwd);
+
+repeat_each(1);
+
+plan tests => repeat_each() * (3 * blocks());
+
+my $pwd = cwd();
+
+our $HttpConfig = qq{
+    lua_package_path "$pwd/lib/?/init.lua;;";
+};
+
+$ENV{TEST_NGINX_RESOLVER} = '8.8.8.8';
+$ENV{TEST_NGINX_MONGO_PORT} ||= 27017;
+
+no_long_string();
+#no_diff();
+
+run_tests();
+
+__DATA__
+
+=== TEST 2: db auth failed
+--- http_config eval: $::HttpConfig
+--- config
+    location /t {
+        content_by_lua '
+            local mongo = require "resty.mongol"
+            conn = mongo:new()
+            conn:set_timeout(1000) 
+
+            ok, err = conn:connect("10.6.2.51")
+            if not ok then
+                ngx.say("connect failed: "..err)
+            end
+
+            local db = conn:new_db_handle("test")
+            local r,err = db:auth("admin", "pass")
+            if not r then ngx.say(err) 
+            else
+                ngx.say(r)
+            end
+        ';
+    }
+--- request
+GET /t
+--- response_body
+auth fails
+--- no_error_log
+[error]
+
+=== TEST 5: is master
+--- http_config eval: $::HttpConfig
+--- config
+    location /t {
+        content_by_lua '
+            local mongo = require "resty.mongol"
+            conn = mongo:new()
+            conn:set_timeout(1000) 
+
+            ok, err = conn:connect("10.6.2.51")
+            if not ok then
+                ngx.say("connect failed: "..err)
+            end
+
+            r, h = conn:ismaster()
+            if not r then
+                ngx.say("query master failed: "..h)
+            end
+
+            ngx.say(r)
+            for i,v in pairs(h) do
+                ngx.say(v)
+            end
+            conn:close()
+        ';
+    }
+--- request
+GET /t
+--- response_body_like
+true
+--- no_error_log
+[error]
+
+=== TEST 6: is not master
+--- http_config eval: $::HttpConfig
+--- config
+    location /t {
+        content_by_lua '
+            local mongo = require "resty.mongol"
+            conn = mongo:new()
+            conn:set_timeout(1000) 
+
+            ok, err = conn:connect("10.6.2.51", 27018)
+            if not ok then
+                ngx.say("connect failed: "..err)
+            end
+
+            r, h = conn:ismaster()
+            if r == nil then
+                ngx.say("query master failed: "..h)
+            end
+
+            ngx.say(r)
+            for i,v in pairs(h) do
+                ngx.say(v)
+            end
+            conn:close()
+        ';
+    }
+--- request
+GET /t
+--- response_body_like
+false
+--- no_error_log
+[error]
+
+=== TEST 7: get primary
+--- http_config eval: $::HttpConfig
+--- config
+    location /t {
+        content_by_lua '
+            local mongo = require "resty.mongol"
+            conn = mongo:new()
+            conn:set_timeout(1000) 
+
+            ok, err = conn:connect("10.6.2.51", 27018)
+            if not ok then
+                ngx.say("connect failed: "..err)
+            end
+
+            r, h = conn:ismaster()
+            if r == nil then
+                ngx.say("query master failed: "..h)
+            end
+
+            if r then ngx.say("already master") return end
+
+            newconn,err = conn:getprimary()
+            if not newconn then
+                ngx.say("get primary failed: "..err)
+            end
+            r, h = newconn:ismaster()
+            if not r then
+                ngx.say("get master failed")
+            end
+
+            ngx.say("get primary")
+            conn:close()
+        ';
+    }
+--- request
+GET /t
+--- response_body
+get primary
+--- no_error_log
+[error]
+
+=== TEST 8: db auth
+--- http_config eval: $::HttpConfig
+--- config
+    lua_code_cache off;
+    location /t {
+        content_by_lua '
+            local mongo = require "resty.mongol"
+            conn = mongo:new()
+            conn:set_timeout(1000) 
+
+            ok, err = conn:connect("10.6.2.51")
+            if not ok then
+                ngx.say("connect failed: "..err)
+            end
+
+            local db = conn:new_db_handle("test")
+            local r,err = db:auth("admin", "admin")
+            if not r then ngx.say("auth failed") end
+            ngx.say(r)
+        ';
+    }
+--- request
+GET /t
+--- response_body
+1
+--- no_error_log
+[error]
+
+
diff --git a/t/cursor.t b/t/cursor.t
index f86e92b..563a05a 100644
--- a/t/cursor.t
+++ b/t/cursor.t
@@ -86,9 +86,6 @@ GET /t
 3
 1
 2
-3
-4
-5
 --- no_error_log
 [error]
 
@@ -258,3 +255,76 @@ sort failed: sort must be an array
 --- no_error_log
 [error]
 
+=== TEST 4: cursor next over limit
+--- http_config eval: $::HttpConfig
+--- config
+    location /t {
+        content_by_lua '
+            local mongo = require "resty.mongol"
+            conn = mongo:new()
+            conn:set_timeout(10000) 
+            local ok, err = conn:connect("10.6.2.51")
+
+            if not ok then
+                ngx.say("connect failed: "..err)
+            end
+
+            local db = conn:new_db_handle("test")
+            local r = db:auth("admin", "admin")
+            if not r then ngx.say("auth failed") end
+            local col = db:get_col("test")
+
+            r, err = col:delete({}, nil, true)
+            if not r then ngx.say("delete failed: "..err) end
+
+            local i, j
+            local t = {}
+            for i = 1,10 do
+                j = 100 - i
+                table.insert(t, {name="dog",n=i,m=j})
+            end
+            r, err = col:insert(t, nil, true)
+            if not r then ngx.say("insert failed: "..err) end
+
+            r = col:find({name="dog"})
+            r:limit(3)
+            for i , v in r:pairs() do
+                ngx.say(v["n"])
+            end
+
+            k,v = r:next()
+            ngx.say(v)
+
+            r = col:find({name="dog"})
+            for i = 1, 10 do
+                k,v = r:next()
+                ngx.say(v["n"])
+            end
+
+            i,v = r:next()
+            ngx.say(v)
+
+            conn:close()
+        ';
+    }
+--- request
+GET /t
+--- response_body
+1
+2
+3
+nil
+1
+2
+3
+4
+5
+6
+7
+8
+9
+10
+nil
+--- no_error_log
+[error]
+
diff --git a/t/gridfs_write.t b/t/gridfs_write.t
index c370016..6fef49f 100644
--- a/t/gridfs_write.t
+++ b/t/gridfs_write.t
@@ -5,7 +5,7 @@ use Cwd qw(cwd);
 
 repeat_each(1);
 
-plan tests => repeat_each() * (4 * blocks());
+plan tests => repeat_each() * (4 * blocks()) - 1;
 
 my $pwd = cwd();
 
@@ -768,7 +768,6 @@ GET /t
 --- output_files
 >>> /tmp/testfile chop
 ABCDEFGHIJKLMNOPQRST
---- ONLY
 --- no_error_log
 [error]
 
diff --git a/t/sanity.t b/t/sanity.t
index 02b5ec3..b58c29a 100644
--- a/t/sanity.t
+++ b/t/sanity.t
@@ -62,41 +62,12 @@ __DATA__
 --- request
 GET /t
 --- response_body
-insert failed: unauthorized
+insert failed: need to login
 0
 dog
 --- no_error_log
 [error]
 
-=== TEST 2: db auth failed
---- http_config eval: $::HttpConfig
---- config
-    location /t {
-        content_by_lua '
-            local mongo = require "resty.mongol"
-            conn = mongo:new()
-            conn:set_timeout(1000) 
-
-            ok, err = conn:connect("10.6.2.51")
-            if not ok then
-                ngx.say("connect failed: "..err)
-            end
-
-            local db = conn:new_db_handle("test")
-            local r,err = db:auth("admin", "pass")
-            if not r then ngx.say(err) 
-            else
-                ngx.say(r)
-            end
-        ';
-    }
---- request
-GET /t
---- response_body
-auth fails
---- no_error_log
-[error]
-
 === TEST 3: socket failed
 --- http_config eval: $::HttpConfig
 --- config
@@ -154,140 +125,6 @@ GET /t
 --- no_error_log
 [error]
 
-=== TEST 5: is master
---- http_config eval: $::HttpConfig
---- config
-    location /t {
-        content_by_lua '
-            local mongo = require "resty.mongol"
-            conn = mongo:new()
-            conn:set_timeout(1000) 
-
-            ok, err = conn:connect("10.6.2.51")
-            if not ok then
-                ngx.say("connect failed: "..err)
-            end
-
-            r, h = conn:ismaster()
-            if not r then
-                ngx.say("query master failed: "..h)
-            end
-
-            ngx.say(r)
-            for i,v in pairs(h) do
-                ngx.say(v)
-            end
-            conn:close()
-        ';
-    }
---- request
-GET /t
---- response_body_like
-true
---- no_error_log
-[error]
-
-=== TEST 6: is not master
---- http_config eval: $::HttpConfig
---- config
-    location /t {
-        content_by_lua '
-            local mongo = require "resty.mongol"
-            conn = mongo:new()
-            conn:set_timeout(1000) 
-
-            ok, err = conn:connect("10.6.2.51", 27018)
-            if not ok then
-                ngx.say("connect failed: "..err)
-            end
-
-            r, h = conn:ismaster()
-            if r == nil then
-                ngx.say("query master failed: "..h)
-            end
-
-            ngx.say(r)
-            for i,v in pairs(h) do
-                ngx.say(v)
-            end
-            conn:close()
-        ';
-    }
---- request
-GET /t
---- response_body_like
-false
---- no_error_log
-[error]
-
-=== TEST 7: get primary
---- http_config eval: $::HttpConfig
---- config
-    location /t {
-        content_by_lua '
-            local mongo = require "resty.mongol"
-            conn = mongo:new()
-            conn:set_timeout(1000) 
-
-            ok, err = conn:connect("10.6.2.51", 27018)
-            if not ok then
-                ngx.say("connect failed: "..err)
-            end
-
-            r, h = conn:ismaster()
-            if r == nil then
-                ngx.say("query master failed: "..h)
-            end
-
-            if r then ngx.say("already master") return end
-
-            newconn,err = conn:getprimary()
-            if not newconn then
-                ngx.say("get primary failed: "..err)
-            end
-            r, h = newconn:ismaster()
-            if not r then
-                ngx.say("get master failed")
-            end
-
-            ngx.say("get primary")
-            conn:close()
-        ';
-    }
---- request
-GET /t
---- response_body
-get primary
---- no_error_log
-[error]
-
-=== TEST 8: db auth
---- http_config eval: $::HttpConfig
---- config
-    lua_code_cache off;
-    location /t {
-        content_by_lua '
-            local mongo = require "resty.mongol"
-            conn = mongo:new()
-            conn:set_timeout(1000) 
-
-            ok, err = conn:connect("10.6.2.51")
-            if not ok then
-                ngx.say("connect failed: "..err)
-            end
-
-            local db = conn:new_db_handle("test")
-            local r,err = db:auth("admin", "admin")
-            if not r then ngx.say("auth failed") end
-            ngx.say(r)
-        ';
-    }
---- request
-GET /t
---- response_body
-1
---- no_error_log
-[error]
 
 === TEST 9: col count
 --- http_config eval: $::HttpConfig
@@ -341,6 +178,7 @@ GET /t
 
             local db = conn:new_db_handle("test")
             local col = db:get_col("test")
+
             r,err = col:update({name="dog"},{name="cat"}, nil, nil, true)
             if not r then ngx.say("update failed: "..err) end
 
@@ -393,7 +231,7 @@ GET /t
 --- request
 GET /t
 --- response_body
-update failed: unauthorized
+update failed: need to login
 1
 cat
 1
@@ -443,7 +281,7 @@ cat
 --- request
 GET /t
 --- response_body
-10
+4
 --- no_error_log
 [error]
 
@@ -471,17 +309,17 @@ GET /t
             col = db:get_col("test")
             col:delete({name="puppy"})
 
-            for i = 1, 3 do
+            for i = 1, 10 do
                 col:insert({{name="puppy", n=i, m="foo"}})
             end
 
-            r = col:find({name="puppy"}, {n=0}, 4)
+            r = col:find({name="puppy"}, {n=0}, 3)
             for i , v in r:pairs() do
                 ngx.say(v["n"])
                 ngx.say(v["name"])
             end
 
-            r = col:find({name="puppy"}, {n=1}, 4)
+            r = col:find({name="puppy"}, {n=1}, 3)
             for i , v in r:pairs() do
                 ngx.say(v["n"])
                 ngx.say(v["name"])
@@ -677,7 +515,7 @@ not found
 --- request
 GET /t
 --- response_body
-delete failed: unauthorized
+delete failed: need to login
 3
 1
 -1
@@ -962,3 +800,50 @@ GET /t
 --- no_error_log
 [error]
 
+=== TEST 21: query by skip and retnum
+--- http_config eval: $::HttpConfig
+--- config
+    location /t {
+        content_by_lua '
+            local mongo = require "resty.mongol"
+            conn = mongo:new()
+            conn:set_timeout(10000) 
+            ok, err = conn:connect("10.6.2.51")
+
+            if not ok then
+                ngx.say("connect failed: "..err)
+            end
+
+            local db = conn:new_db_handle("test")
+            local col = db:get_col("test")
+
+            r = db:auth("admin", "admin")
+            if not r then ngx.say("auth failed") end
+
+            r, err = col:delete({}, nil, true)
+            if not r then ngx.say("delete failed: "..err) end
+
+            local t = {a=1,b=2}
+            
+            for i = 1, 10 do
+                col:insert({{name="puppy"}})
+            end
+
+            sel = {name="puppy"}
+            id, results, t = col:query(sel,{_id=1},0,1)
+            ngx.say(#results)
+
+            id, results, t = col:query(sel,{_id=1},5,5)
+            ngx.say(#results)
+
+            conn:close()
+        ';
+    }
+--- request
+GET /t
+--- response_body
+1
+5
+--- no_error_log
+[error]
+