Mongo Go驱动程序的DocumentCount不支持$ nearSphere

Question

I am working on geo location query where I want to get total number of collections that satisfy geo location query. Mongo go library provides Document Count method with doesn't support filter based on geo location.

The error I am getting is: (BadValue) $geoNear, $near, and $nearSphere are not allowed in this context

filter := bson.D{
    {
        Key: "address.location",
        Value: bson.D{
            {
                Key: "$nearSphere",
                Value: bson.D{
                    {
                        Key: "$geometry",
                        Value: bson.D{
                            {
                                Key:   "type",
                                Value: "Point",
                            },
                            {
                                Key:   "coordinates",
                                Value: bson.A{query.Longitude, query.Latitude},
                            },
                        },
                    },
                    {
                        Key:   "$maxDistance",
                        Value: maxDistance,
                    },
                },
            },
        },
    },
}
collection := db.Database("catalog").Collection("restaurant")
totalCount, findError := collection.CountDocuments(ctx, filter)

Answer 1

(BadValue) $geoNear, $near, and $nearSphere are not allowed in this context

You're getting this message due to the restricted use of db.collection.countDocuments().

The method countDocuments() essentially wraps aggregation pipeline $match and $group. See The Mechanics of countDocuments() for more information. There are a number of query operators that are restricted : Query Restrictions, one of them being $nearSphere operator.

An alternative is to use [$geoWithin] and $centerSphere:

filter := bson.D{ 
  { Key: "address.location", 
    Value: bson.D{ 
        { Key: "$geoWithin", 
            Value: bson.D{ 
                { Key: "$centerSphere", 
                  Value: bson.A{ 
                            bson.A{ query.Longitude, query.Latitude } , 
                            maxDistance}, 
                }, 
            },
        },
    },
  }}

Note that the maxDistance in spherical geometry has to be in a radius. You need to convert the distance, for example 10/6378.1 for 10 kilometres please see Calculate Distance using Spherical Geometry for more information.

Also worth mentioning that although $centerSphere works without having a geospatial index, geospatial indexes support much faster queries than the unindexed equivalents.