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roman-roman
roman-roman

Reputation: 2796

MongoDB geospacial query

I use mongo's "$near" query, it works as expected and saves me a lot of time.

Now I need to perform something more complicated. Imagine, we have a collection of "checkins" (let's use foursquare notation), that contains the geospacial information (nothing unusual: just lat and lng) and time. Given the checkins by two people, how do I find their "were near to each other" checkins? I mean, e.g.: "1/23/12 you've been 100 meters away"

The easiest solution is to select all the checkins by the first user and find nearest checkin for each first user's checkin on the framework side (I use ruby). But is it the most efficient solution? Do you have better ideaas? May be I need some kind of a special index?

Best, Roman

Upvotes: 0

Views: 116

Answers (1)

William Z
William Z

Reputation: 11129

The MongoDB GeoSpatial indexes provide two types of queries: $near and $within. The $near query returns all points in the database that are within a certain range of a requested point, while the $within query lists all points in the database that are inside of a particular area (box, circle, or arbitrary polygon).

MongoDB does not currently provide a query that will return all points that are within a certain distance of any member of another set of points, which is what you seem to want.

You could conceivably use the point data from user1 to build a polygon describing the "area of interest" and then use the $within query to see if there were any checkins by other people inside of that area. If you use a compound index on location & date, you could even restrict the query to folks who were inside of that area on a particular day.

References:

Upvotes: 1

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