MongoDB's projection feature being overlooked

I am completely new to Mongo, so I'm sure there's something obvious that I'm missing. Despite searching online, I can't figure out why my MongoDB query in a JavaScript file isn't working.

Strangely enough, the projection part of the query is being ignored by Mongo, everything else seems to be functioning correctly.


criteria = ' { "powersave_enabled" : false, "tx_rate" : { $lt : 26000 }, "rx_rate" : { $lt : 26000 }, "btyes-r" : { $ne: 0 } } ';

projection = ' {"_id":0, "hostname" : 1, "rssi" : 1, "mac" : 1, "ap_mac" : 1, "noise" : 1} ';

command = criteria + ', ' + projection;

accessPoints = db.cache_sta.find(command);

while (accessPoints.hasNext()){
  printjson( accessPoints.next() );
}

After printing and testing the command in mongo myself, it appears to be correct. There must be an issue with the JS code.

Any help would be greatly appreciated!

javascriptmongodb

Answer №1

It is recommended to pass the criteria and the projection as objects instead of concatenating them, like shown below:

criteria = { "powersave_enabled" : false, "tx_rate" : { $lt : 26000 }, "rx_rate" : { $lt : 26000 }, "btyes-r" : { $ne: 0 } };

projection = {"_id":0, "hostname" : 1, "rssi" : 1, "mac" : 1, "ap_mac" : 1, "noise" : 1};

accessPoints = db.cache_sta.find(criteria, projection);

while (accessPoints.hasNext()){
     printjson( accessPoints.next() );
}

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