Geonear sort by distance and time

Question

I have the following data:

{ 
    "_id" : ObjectId("55a8c1ba3996c909184d7a22"),
    "uid" : "1db82e8a-2038-4818-b805-76a46ba62639",
    "createdate" : ISODate("2015-07-17T08:50:02.892Z"),
    "palce" : "aa",
    "sex" : 1,
    "longdis" : 1,
    "location" : [ 106.607312, 29.575281 ]
}
{ 
    "_id" : ObjectId("55a8c1ba3996c909184d7a24"),
    "uid" : "1db82e8a-2038-4818-b805-76a46ba62639",
    "createdate" : ISODate("2015-07-17T08:50:02.920Z"),
    "palce" : "bbb",
    "sex" : 1,
    "longdis" : 1,
    "location" : [ 106.589896, 29.545098 ]
}
{
    "_id" : ObjectId("55a8c1ba3996c909184d7a25"),
    "uid" : "1db82e8a-2038-4818-b805-76a46ba62639",
    "createdate" : ISODate("2015-07-17T08:50:02.922Z"),
    "palce" : "ccc",
    "sex" : 1,
    "longdis" : 1,
    "location" : [ 106.590758, 29.566713 ]
}
{
    "_id" : ObjectId("55a8c1ba3996c909184d7a26"),
    "uid" : "1db82e8a-2038-4818-b805-76a46ba62639",
    "createdate" : ISODate("2015-07-17T08:50:02.923Z"),
    "palce" : "ddd",
    "sex" : 1, 
    "longdis" : 1, 
    "location" : [ 106.637039, 29.561436 ]
}
{
    "_id" : ObjectId("55a8c1bc3996c909184d7a27"),
    "uid" : "1db82e8a-2038-4818-b805-76a46ba62639",
    "createdate" : ISODate("2015-07-17T08:50:04.499Z"),
    "palce" : "eee",
    "sex" : 1,
    "longdis" : 1,
    "location" : [ 106.539522, 29.57929 ]
}
{ 
    "_id" : ObjectId("55a8d12e78292fa3837ebae4"),
    "uid" : "1db82e8a-2038-4818-b805-76a46ba62639",
    "createdate" : ISODate("2015-07-17T09:55:58.947Z"),
    "palce" : "fff",
    "sex" : 1,
    "longdis" : 1,
    "location" : [ 106.637039, 29.561436 ]
}

I want to first of all, sort by the distance, if the distance is the same, sort by the time.

my command :

db.runCommand( { 
   geoNear: "paging", 
   near: [106.606033,29.575897 ],
   spherical : true,
   maxDistance : 1/6371,
   minDistance:0/6371,
   distanceMultiplier: 6371,
   num:2,
   query: {'_id': {'$nin': []}} 
})

or

db.paging.find({
   'location':{
       $nearSphere: [106.606033,29.575897],
       $maxDistance:1
   }
}).limit(5).skip((2 - 1) * 2).sort({createdate:-1})

How can I sort on both "nearest" and "createddate"?

Answer 1

The correct query to use here uses the aggregation framework which has the $geoNear pipeline stage to assist with this. It's also the only place you get to "sort" by multiple keys, as unforntunately the "geospatial" $nearSphere does not have a "meta" projection for "distance" like $text has a "score".

Also the geoNear database command you are using can also not be used with "cursor" .sort() in that way either.

db.paging.aggregate([
    { "$geoNear": {
        "near": [106.606033,29.575897 ],
        "spherical": true,
        "distanceField": "distance",
        "distanceMuliplier": 6371,
        "maxDistance": 1/6371
    }},
    { "$sort": { "distance": 1, "createdate": -1 } },
    { "$skip": ( 2-1 ) * 2 },
    { "$limit": 5 }
])

That is the equivalent of what you are trying to do.

With the aggregation framework you use the "pipeline operators" instead of "cursor modifiers" to do things like $sort, $skip and $limit. Also these must be in a Logical order, whereas the cursor modifiers generally work it out.

It's a "pipeline", just like "Unix pipe". |

Also, be careful with "maxDistance" and "distanceMuliplier". Since your co-ordinates are in "legacy co-ordinate pairs" and not GeoJSON format, then the distances are measured in "radians". If you have GeoJSON stored location data then the result is returned in "meters".