Filtering & sorting by dates in MongoDB's oplog -

i'm trying filter oplog.rs view operations logged after date. comparison operators don't seem work dates in mongodb:

db['oplog.rs'].find({ts: {$gte: isodate("2014-12-15t00:00:00z")}}) 

what's confusing lot of online sources saying way not working. want return results ts field @ least december 15th or more recent, getting results before period. if switch $gte $lte no results @ displayed, though there entries both before , after specified date.

also, can't seem sort results either. if try this:

db['oplog.rs'].find().sort({ts: -1}) 

i this:

error: {     "$err" : "runner error: overflow sort stage buffered data usage of 33566005 bytes exceeds internal limit of 33554432 bytes",     "code" : 17144 } 

if filter results make them more recent, hoping overcome sorting error, can't mongodb's basic operators. how can filter results of find operation date?

comparion operators work fine date, ts timestamp object - not date.

your query needs this:

db['oplog.rs'].find({ts: {$gte: timestamp(isodate("2014-12-15t00:00:00z").gettime(),0)}}) 

this creates timestamp object based on isodate , uses in query.