MongoDB takes long time to return geolocation query.

[aditya]

I have events collection in database on which I have applied following compound index

{ "coordinates":"2d","start_time":1 }

The coordinates are regular latitude-longitude and start_time is unix time. I have about 4,00,000 events in collection. Now I throw following command to find nearby events

db.events.find({ "coordinates": { "$near": [ 77.22445, 28.63576 ] }, "start_time": { "$gt": 1357491649 } });

This query sometimes returns result after 20 seconds!!!

Please help me how to optimize this query? 

[aditya]

Even when I throw 

db.events.find({ "coordinates": { "$near": [ 77.22445, 28.63576 ] }});

query which is without start_time, it takes more than 1 second. 

Please help me. This is hindering my site speed.

[Justin Case]

Could you post the .explain() output?

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[aditya]

My log shows this 

Sun Jan  6 22:50:17 [conn8] command cityevent.$cmd command: { count: "events", query: { start_time: { $gt: 1357492788 }, coordinates: { $nearSphere: [ 72.61667, 23.03333 ] } } } ntoreturn:1 keyUpdates:0 locks(micros) r:29019506 reslen:48 29019ms

explain output is 

{

"cursor" : "GeoSearchCursor",

"isMultiKey" : false,

"n" : 100,

"nscannedObjects" : 100,

"nscanned" : 100,

"nscannedObjectsAllPlans" : 100,

"nscannedAllPlans" : 100,

"scanAndOrder" : false,

"indexOnly" : false,

"nYields" : 0,

"nChunkSkips" : 0,

"millis" : 1,

"indexBounds" : {

},

"server" : "aditya-laptop:27017"

}

[Justin Case]

What is the query you ran explain on? According to the output it completed in 1ms.

[aditya]

That is another problem. I don't know why it gives output 1ms when I can even count time in my wrist watch. You can also see the log of mongodb.log file for same query.

Sun Jan  6 22:57:15 [conn10] query cityevent.events query: { query: { start_time: { $gt: 1357492788.0 }, coordinates: { $nearSphere: [ 72.61667, 23.03333 ] } }, $explain: true } ntoreturn:0 ntoskip:0 nscanned:100 keyUpdates:0 locks(micros) r:46155752 nreturned:1 reslen:389 46155ms

[Hari Khalsa]

If you don't need the points sorted by distance, consider bounding the query by doing a $center or $centerSphere, or if you do need them sorted, try adding a maxDistance to the near?  $near might have to look quite far away to find points.

If your points are meant to be latitude and longitude, there is new geospatial functionality coming out in 2.4 which should be much faster for these types of queries.

[aditya]

I always use maxdistance there. Anyway, will wait till 2.4 is released. Thanks :-)