Shashank Tiwari goes through the basics of Geolocation queries and indexing in MongoDB.

1. GEOLOCATION IN
MONGODB
{ name: ‘Shashank Tiwari’, web: ‘shanky.org’}
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2. WHO AM I?
Entrepreneur, developer, author
Most recent book: Professional NoSQL (Wiley, 2011)
Co-founder :
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3. DEGREES OF MEASURE
Latitude
Longitude
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4. DEGREE OF LONGITUDE
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5. GEO IN MONGO
Is a world in 2D
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6. 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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7. INDEX
db.places.ensureIndex( { loc : "2d" } )
1 geospatial index per collection
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8. INDEX RANGE
db.places.ensureIndex( { loc : "2d" } , { min : -500 , max :
500 } )
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9. INDEX PRECISION
db.places.ensureIndex( { loc : "2d" } , { bits : 26 } )
Geo-hash precision of 26bits ~ 2 feet
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10. 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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11. EXPLAIN QUERY PLAN
db.places.find({ loc : [ 37.407202, -122.10716 ]}).explain();
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12. COMPOUND INDEX
db.places.ensureIndex( { loc : "2d", name : 1 } )
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13. NEAR QUERY
db.places.find({ loc : { $near : [ 37.407202, -122.10716 ]}});
Returns points sorted by distance
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14. 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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15. GEONEAR QUERY
db.runCommand({ geoNear : "places", near : [37.407202,
-122.10716], num : 5 });
also gives the distance
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16. 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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17. WITHIN A BOX
db.places.find({ loc : { $within : { $box : [[39.589821,
-122.438831], [37.485200, -122.228438]] }}});
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18. WITHIN A CIRCLE
db.places.find({ loc : { $within : { $center : [[39.589821,
-122.438831], 10] }}});
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19. WITHIN A POLYGON
Polygon shapes currently cannot be indexed
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20. SPHERICAL SUPPORT
geoNear -- spherical : true
$nearSphere
$centerSphere
Order is important, very important -- longitude, latitude
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21. MULTI LOCATIONS
db.places.insert({ placesVisitedToday : [ { name : "San
Antonio Caltrain", loc : [37.407202, -122.10716] }, { name :
"Kixeye", loc : [37.7906672, -122.403256] } ] })
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22. QUERY MULTI LOC
db.places.ensureIndex( { " placesVisitedToday.loc " : "2d"} )
use uniqueDocs : true to get unique documents
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23. Wednesday, November 28, 12

24. Wednesday, November 28, 12

25. NEXT TALK
More details and some about GIS too!
SV MongoDB User Group @ Palo Alto -- January Meetup
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26. THANKS
More questions? web: shanky.org | twitter : @tshanky
Want to join the alpha program?
doaround.com
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