GEOLOCATION IN MONGODB

{ name: ‘Shashank Tiwari’, web: ‘shanky.org’}

Wednesday, January 16, 13

WHO AM I?

Entrepreneur, developer, author

Most recent book: Professional NoSQL (Wiley, 2011)

Founder : WhatNext Labs, creators of

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DEGREES OF MEASURE

Latitude

Longitude

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DEGREE OF LONGITUDE

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GEO IN MONGO

Is a world in 2D

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MONGO DOC WITH LOC

{ loc : [37.407202, -122.10716] }

{ loc : { x: 37.407202, y: -122.10716} }

{ loc : { lat: 37.407202, lon: -122.10716} }

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INDEX

db.places.ensureIndex( { loc : "2d" } )

1 geospatial index per collection

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INDEX RANGE

db.places.ensureIndex( { loc : "2d" } , { min : -500 , max : 500 } )

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INDEX PRECISION

db.places.ensureIndex( { loc : "2d" } , { bits : 26 } )

Geo-hash precision of 26bits ~ 2 feet

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EXACT QUERIES

> db.places.find({ loc : [ 37.407202, -122.10716 ]});

{ "_id" : ObjectId("50b69e66e6945f62a019f3a4"), "name" : "San Antonio Caltrain", "loc" : [ 37.407202, -122.10716 ] }

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EXPLAIN QUERY PLAN

db.places.find({ loc : [ 37.407202, -122.10716 ]}).explain();

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COMPOUND INDEX

db.places.ensureIndex( { loc : "2d", name : 1 } )

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NEAR QUERY

db.places.find({ loc : { $near : [ 37.407202, -122.10716 ]}});

Returns points sorted by distance

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WITH MAXDISTANCE

db.places.find({ loc : { $near : [ 37.407202, -122.10716 ], $maxDistance : 0.05}});

What is the unit of maxDistance? -- for latitude & longitude 1 degree ~ 69 miles

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GEONEAR QUERY

db.runCommand({ geoNear : "places", near : [37.407202, -122.10716], num : 5 });

also gives the distance

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MORE WITH GEONEAR

db.runCommand({ geoNear : "places", near : [37.407202, -122.10716], num : 5, type : “DO” });

parameters: near, num, maxDistance, query

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WITHIN A BOX

db.places.find({ loc : { $within : { $box : [[39.589821, -122.438831], [37.485200, -122.228438]] }}});

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WITHIN A CIRCLE

db.places.find({ loc : { $within : { $center : [[39.589821, -122.438831], 10] }}});

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WITHIN A POLYGON

Polygon shapes currently cannot be indexed

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SPHERICAL SUPPORT

geoNear -- spherical : true

$nearSphere

$centerSphere

Order is important, very important -- longitude, latitude

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MULTI LOCATIONS

db.places.insert({ placesVisitedToday : [ { name : "San Antonio Caltrain", loc : [37.407202, -122.10716] }, { name : "Datapipe", loc : [37.3336641, -121.8887072] } ] })

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QUERY MULTI LOC

db.places.ensureIndex( { " placesVisitedToday.loc " : "2d"} )

use uniqueDocs : true to get unique documents

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NEXT TALK

Join me to learn MongoDB in an hour!

Coming soon : Feb 1, 2013

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THANKS

More questions? web: shanky.org | twitter : @tshanky | email: st@treasuryofideas.com

Download and play with on Google Play and coming soon to the AppStore.

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