slow Mongodb $near search with additional criteria - mongodb

Question

I have a collection, the data look like this:
{
"_id" : ObjectId("4e627655677c27cf24000000"),
"gps" : {
"lng" : 116.343079,
"lat" : 40.034283
},
"lat" : 1351672296
}
And I build a compound index:
{
"v" : 1,
"key" : {
"gps" : "2d",
"lat" : 1
},
"ns" : "test.user",
"name" : "gps__lat_1"
}
A pure $near query like below can be very fast ( < 20ms ):
>db.user.find({"gps":{"$near":{"lng":116.343079,"lat":40.034283}}}).explain()
{
"cursor" : "GeoSearchCursor",
"nscanned" : 100,
"nscannedObjects" : 100,
"n" : 100,
"millis" : 23,
"nYields" : 0,
"nChunkSkips" : 0,
"isMultiKey" : false,
"indexOnly" : false,
"indexBounds" : {
}
}
But the query with "lat" criteria is very slow ( 900ms+ ):
>db.user.find({"gps":{"$near":{"lng":116.343079,"lat":40.034283}},"lat":{"$gt":1351413167}}).explain()
{
"cursor" : "GeoSearchCursor",
"nscanned" : 3,
"nscannedObjects" : 3,
"n" : 3,
"millis" : 665,
"nYields" : 0,
"nChunkSkips" : 0,
"isMultiKey" : false,
"indexOnly" : false,
"indexBounds" : {
}
}
Can anybody explain this? Great thx!

Answer 1

I updated my Mongodb up to 2.2.0, the problem disappeared.
127.0.0.1/test> db.user.find({gps:{$near:[116,40]},lat:{$gt:1351722342}}).explain()
{
"cursor" : "BasicCursor",
"isMultiKey" : false,
"n" : 0,
"nscannedObjects" : 0,
"nscanned" : 0,
"nscannedObjectsAllPlans" : 0,
"nscannedAllPlans" : 0,
"scanAndOrder" : false,
"indexOnly" : false,
"nYields" : 0,
"nChunkSkips" : 0,
"millis" : 0,
"indexBounds" : {
},
"server" : "zhangshenjiamatoMacBook-Air.local:27017"
}

Answer 2

From the explain above, it doesn't look like the geoIndex is being used at all - also, it looks like the above query didn't return any results!
If your query is using the 2d index, the explain should contain:
"cursor" : "GeoSearchCursor"
Can you check if upgrading to 2.2.0 really solved your issue? :)
Sundar