doc.cursor.id ~= cbson.uint(0)

[misschuer]

function _M.aggregate(self, pipeline, opts)
..............................
-- cursor
return cursor.new(self, {}, {}, false, doc.cursor.id):add_batch(doc.cursor.firstBatch)
end

OR

function _M.aggregate(self, pipeline, opts)
..............................
-- cursor
return cursor.new(self, {}, {}, false, cbson.uint(doc.cursor.id)):add_batch(doc.cursor.firstBatch)
end

[isage]

What?

[misschuer]

sorry for

[misschuer]

when i use 'aggregate' to search data, then program runs err.
so i explain the code, then i found 'doc.cursor.id' is not equal to cbson.uint(0) forever.
i changed the 'doc.cursor.id' to 'cbson.uint(doc.cursor.id)' and it runs well.
is this a bug or i use it in wrong way? it is in collection.lua line 372.
forgive my poor english.

[isage]

Can you provide an example of how you use aggregate, and what error it returns?

[misschuer]

the pipeline:
local wheres = {
[ 1 ] = {
["$match"] = {
guid = guid,
}
},
[ 2 ] = {
["$sort"] = {
_id = -1,
},
},
[ 3 ] = {
["$skip"] = skips,
},
[ 4 ] = {
["$limit"] = limits,
},
[ 5 ] = {
["$lookup"] = {
from = user_table_name,
localField = "guid",
foreignField = "_id",
as = "docs1",
}
},
[ 6 ] = {
["$project"] = {
_id = 1,
guid = 1,
docs1 = {
name = 1,
avatar = 1,
},
}
},
}

This is copy from collection.lua

function _M.aggregate(self, pipeline, opts)
local opts = opts or {}
opts.pipeline = pipeline
if not opts.explain then
opts.cursor = {}
end

local doc, err = self._db:cmd(
{ aggregate = self.name },
opts
)
if not doc then
return nil, err
end

if opts.explain then
return doc
end

-- collection
if opts.pipeline[#opts.pipeline]['$out'] then
return self.new(opts.pipeline[#opts.pipeline]['$out'], self._db)
end

--############### i debug it here
ngx.log(ngx.ERR, "cursor_id = ", tostring(doc.cursor.id))
-- cursor
return cursor.new(self, {}, {}, false, doc.cursor.id):add_batch(doc.cursor.firstBatch)
end

the log file said
2018/07/12 20:52:15 [error] 27564#27564: *539 [lua] collection.lua:372: aggregate(): cursor_id = 0
2018/07/12 20:52:15 [error] 27564#27564: *539 [lua] utils.lua:425: print_err_format(): err : wrong cursor id

then i debug in cursor.lua
function _M.next(self)
......
ngx.log(ngx.ERR, tostring(self._id))
if (not self._started) and (self._id == cbson.uint(0)) then
.......
elseif #self._docs == 0 and self._id ~= cbson.uint(0) then
---############## Notice: because self._id is always 0 not eq to cbson.uint(0), it runs this logical and then throwed 'wrong cursor id' exception

if check_bit(flags, 0) then -- QueryFailure
  return nil, "wrong cursor id"
end

elseif #self._docs == 0 then--or self._id == cbson.uint(0) then
return nil, "no more data"
end
.....
end