利用js代码从mongodb中导出查询数据到文件中
var c = db.list_users_sponsor_listing.find({sponsorsListing:{$ne:null}});
while(c.hasNext()) {
    printjson(c.next());
}
mongo localhost:27017/ghtorrent0619 sponsorsListing_notnull.js > sponsorsListing_notnull.json