The document describes MongoDB's GridFS specification for storing and retrieving files that exceed the BSON document size limit of 16MB. It explains that GridFS splits files into chunks, which are stored as individual documents, and maintains metadata about the file such as length, MD5, and filename in a separate collection. It provides examples of using the mongofiles command line tool to list, search, put, and get files from GridFS.

11. {
"_id" : <unspecified>, //file ID
"length" : data_number, // bytes
"chunkSize" : data_number, // :256KB
"uploadDate" : data_date, //file
"md5" : data_string //"filemd5"
}

12. {
"filename" : data_string,
"contentType" : data_string,
"aliases" : data_array of data_string,
"metadata" : data_object,
}

13. {
"_id" : <unspecified>, //chunk ID
"files_id" : <unspecified>, //file _id
"n" : chunk_number, //0 chunk
0,1,2... chunk
"data" : data_binary, // BSON
}

14. > db.fs.chunks.ensureIndex(
{files_id:1, n:1}, {unique: true});
> db.fs.chunks.findOne({files_id: myFileID, n: 0});

15. ➜ ~ mongofiles --help
usage: mongofiles [options] command [gridfs filename]
command:
one of (list|search|put|get)
list - file
search - file
put - file
get - file
delete - file

16. ➜ ~ mongofiles list
connected to: 127.0.0.1
➜ ~ mongofiles put ByeForNow.mp3
connected to: 127.0.0.1
added file: { _id: ObjectId('4df17f8d9d47ba5c0247e72e'),
filename: "ByeForNow.mp3", chunkSize: 262144, uploadDate:
new Date(1307672462538), md5:
"9ee9472200a2e18bf376ce622c3b0055", length: 11183104 }
done!
➜ ~ mongofiles list -v // -v
Fri Jun 10 11:21:05 creating new connection to:127.0.0.1
Fri Jun 10 11:21:05 BackgroundJob starting:
connected to: 127.0.0.1
ByeForNow.mp3 11183104

17. ➜ ~ mongofiles put Maria.mp3
connected to: 127.0.0.1
added file: { _id: ObjectId('4df181fc5e354129e833193f'),
filename: "Maria.mp3", chunkSize: 262144, uploadDate: new
Date(1307673086293), md5:
"9d4f424fa1843711e196e502d8a00183", length: 12225353 }
done!
➜ ~ mongofiles list
connected to: 127.0.0.1
ByeForNow.mp3 11183104
Maria.mp3 12225353
➜ ~ mongofiles list M
connected to: 127.0.0.1
Maria.mp3 12225353
➜ ~ mongofiles search .mp3
connected to: 127.0.0.1
ByeForNow.mp3 11183104
Maria.mp3 12225353

18. ➜ ~ mkdir tmp // get
➜ ~ cd tmp
➜ mongofiles get Maria.mp3
connected to: 127.0.0.1
done write to: Maria.mp3
➜ ls
Maria.mp3
➜ mongofiles get Bye
ERROR: file not found
➜ mongofiles get ByeForNow.mp3
done write to: ByeForNow.mp3
➜ md5 Maria.mp3
MD5 (Maria.mp3) = 9d4f424fa1843711e196e502d8a00183
➜ md5 ../Maria.mp3
MD5 (../Maria.mp3) = 9d4f424fa1843711e196e502d8a00183

19. > db.fs.files.find().forEach(printjson)
{
"_id" : ObjectId("4df17f8d9d47ba5c0247e72e"),
"filename" : "ByeForNow.mp3",
"chunkSize" : 262144,
"uploadDate" : ISODate("2011-06-10T02:21:02.538Z"),
"md5" : "9ee9472200a2e18bf376ce622c3b0055",
"length" : 11183104
}
{
"_id" : ObjectId("4df181fc5e354129e833193f"),
"filename" : "Maria.mp3",
"chunkSize" : 262144,
"uploadDate" : ISODate("2011-06-10T02:31:26.293Z"),
"md5" : "9d4f424fa1843711e196e502d8a00183",
"length" : 12225353
}

20. > db.fs.chunks.findOne(
{n:0,files_id:ObjectId("4df181fc5e354129e833193f")})
{
"_id" : ObjectId("4df181fcd40994ca1de28d09"),
"files_id" : ObjectId("4df181fc5e354129e833193f"),
"n" : 0,
"data" : BinData(0,"SUQzAwAAAABQdlRSQ0sAAAACAAAAM1RJVDIA
AAAHAAAAg32DioNBVUZJRAAAAGYAAGh0dHA6Ly93d3cuY2RkYi5jb20vaWQ
zL3RhZ2luZm8xLmh0bWwAM0NEM00xMTBRMjA3NTYwOTc4VjY4MTBCQTlBNj
UzN0JCQUQ1QTgyOUE4NTRCRkQ2QTdBRjNQOAAAAAAAAAAAAEdFT0IAACNgA
AAAYXBwbGljYX...)
}

21. > db.fs.chunks.ensureIndex({files_id: 1});
> db.runCommand({ shardcollection : "test.fs.chunks", key :
{ files_id : 1 }})
{ "collectionsharded" : "test.fs.chunks", "ok" : 1 }

22. MongoDB GridFS

23. Replace Amazon S3 with MongoDB GridFS and Grails

26. { loc : [ 50 , 30 ] }
{ loc : { x : 50 , y : 30 } }
{ loc : { foo : 50 , y : 30 } }
{ loc : { long : 40.739037, lat: 73.992964 } }

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

28. db.places.find( { loc : [50,50] } )
db.places.find( { loc : { $near : [50,50] } } )
db.places.find( { loc : { $near : [50,50] } } ).limit(20)
db.places.find( { loc : { $near : [50,50] ,
$maxDistance : 5 } } ).limit(20)

29. //
> box = [[40.73083, -73.99756], [40.741404, -73.988135]]
> db.places.find({"loc" : {"$within" : {"$box" : box}}})
//
> center = [50, 50]
> radius = 10
> db.places.find({"loc" : {"$within" : {"$center" : [center, radius]}}})
// v1.9
> polygonA = [ [ 10, 20 ], [ 10, 40 ], [ 30, 40 ], [ 30, 20 ] ]
> polygonB = { a : { x : 10, y : 20 }, b : { x : 15, y : 25 }, c : { x :
20, y : 20 } }
> db.places.find({ "loc" : { "$within" : { "$polygon" : polygonA } } })
> db.places.find({ "loc" : { "$within" : { "$polygon" : polygonB } } })

30. > db.runCommand( { geoNear : "places" , near : [ 50 , 50 ], num : 10,
query : { type : "museum" } } );
{
"ns" : "test.places",
"near" : "1100110000001111110000001111110000001111110000001111",
"results" : [
{
"dis" : 69.29646421910687,
"obj" : {
"_id" : ObjectId("4b8bd6b93b83c574d8760280"),
"y" : [
1,
1
],
"category" : "Coffee"
}
},
{
"dis" : 69.29646421910687,
"obj" : {
"_id" : ObjectId("4b8bd6b03b83c574d876027f"),
1
...}

31. MongoDB

33. > db.points.insert({ pos : { long : 30, lat : 30 } })
> db.points.insert({ pos : { long : -10, lat : -20 } })
> db.points.ensureIndex({ pos : "2d" })
> db.points.find({ pos: { $nearSphere: [0,0], $maxDistance : 0.4 } })
{ "_id" : ObjectId("4df11e47b8e84370f84afdd3"), "pos" : { "long" : -10,
"lat" : -20 } }

34. > var earthRadius = 6378 // km
> var range = 3000 // km
> distances = db.runCommand({ geoNear : "points", near : [0, 0], spherical :
true, maxDistance : range / earthRadius }).results
[
{
"dis" : 0.3886630122897946, //
"obj" : {
"_id" : ObjectId("4df11e47b8e84370f84afdd3"),
"pos" : {
"long" : -10,
"lat" : -20
}
}
}
]
> pointDistance = distances[0].dis * earthRadius
2478.89269238431 // km

43. http://www.slideshare.net/doryokujin/mongo-sharding

46. ~ mkdir -p shard/shard00
~ mkdir -p shard/shard01
~ mkdir -p shard/shard02
~ mkdir -p shard/config
~ mongod --shardsvr --port 27017 --dbpath shard/shard00
~ mongod --shardsvr --port 27018 --dbpath shard/shard01
~ mongod --shardsvr --port 27019 --dbpath shard/shard02
~ mongod --configsvr --port 27020 --dbpath shard/config
~ mongos --configdb localhost:27020 --port 27021

47. ➜ ~ mongo localhost:27021 // mongos
MongoDB shell version: 1.8.0
connecting to: localhost:27021/test
> show dbs
config 0.1875GB // sharding
> db.adminCommand( { addshard: "localhost:27017", name: "shard00" } )
{ "shardAdded" : "shard00", "ok" : 1 }
> db.adminCommand( { addshard: "localhost:27018", name: "shard01" } )
{ "shardAdded" : "shard01", "ok" : 1 }
> db.adminCommand( { addshard: "localhost:27019", name: "shard02" } )
{ "shardAdded" : "shard02", "ok" : 1 }

48. // mongos
> db.adminCommand( { enablesharding : "test" } )
{ "ok" : 1 }
> db.adminCommand( { moveprimary : "test", to : "shard02" } );
{ "primary " : "shard02:localhost:27019", "ok" : 1 }
> db.adminCommand( { shardcollection : "test.myshard", key : { n : 1 } } )
{ "collectionsharded" : "test.myshard", "ok" : 1 }

49. // mongos
> db.adminCommand({split : "test.myshard", middle : { n: 0 } } )
{ "ok" : 1 }
> db.adminCommand({split : "test.myshard", middle : { n: 1 } } )
{ "ok" : 1 }
> db.adminCommand({split : "test.myshard", middle : { n: 2 } } )
{ "ok" : 1 }

50. > db.printShardingStatus() //
--- Sharding Status ---
sharding version: { "_id" : 1, "version" : 3 }
shards:
{ "_id" : "shard00", "host" : "localhost:27017" }
{ "_id" : "shard01", "host" : "localhost:27018" }
{ "_id" : "shard02", "host" : "localhost:27019" }
databases:
{ "_id" : "admin", "partitioned" : false, "primary" : "config" }
{ "_id" : "test", "partitioned" : true, "primary" : "shard02" }
test.myshard chunks:
shard02 4
{ "n" : { $minKey : 1 } } -->> { "n" : 0 } on : shard02 { "t" : 1000, "i" : 1 }
{ "n" : 0 } -->> { "n" : 1 } on : shard02 { "t" : 1000, "i" : 3 }
{ "n" : 1 } -->> { "n" : 2 } on : shard02 { "t" : 1000, "i" : 5 }
{ "n" : 2 } -->> { "n" : { $maxKey : 1 } } on : shard02 { "t" : 1000, "i" : 6 }

51. // mongos
> db.adminCommand({moveChunk: "test.myshard", find: { n: 0 }, to: "shard00" });
{ "millis" : 1051, "ok" : 1 }
> db.adminCommand({moveChunk: "test.myshard", find: { n: 1 }, to: "shard01" });
{ "millis" : 1046, "ok" : 1 }
> db.adminCommand({moveChunk :"test.myshard", find: { n: 2 }, to: "shard02" });
{ "ok" : 0, "errmsg" : "that chunk is already on that shard" }

52. > db.printShardingStatus()
--- Sharding Status ---
sharding version: { "_id" : 1, "version" : 3 }
shards:
{ "_id" : "shard00", "host" : "localhost:27017" }
{ "_id" : "shard01", "host" : "localhost:27018" }
{ "_id" : "shard02", "host" : "localhost:27019" }
databases:
{ "_id" : "admin", "partitioned" : false, "primary" : "config" }
{ "_id" : "test", "partitioned" : true, "primary" : "shard02" }
test.myshard chunks:
shard02 2
shard00 1
shard01 1
{ "n" : { $minKey : 1 } } -->> { "n" : 0 } on : shard02 { "t" : 3000, "i" : 1 }
{ "n" : 0 } -->> { "n" : 1 } on : shard00 { "t" : 2000, "i" : 0 }
{ "n" : 1 } -->> { "n" : 2 } on : shard01 { "t" : 3000, "i" : 0 }
{ "n" : 2 } -->> { "n" : { $maxKey : 1 } } on : shard02 { "t" : 1000, "i" : 6 }

53. // mongos
> for(var m=0; m<100; m++){ db.myshard.insert({n: m % 3}) } // n =0,1,2,0,1,...
> printShardingSizes() // Shard
...
test.myshard chunks:
{ "n" : { $minKey : 1 } } -->> { "n" : 0 } on : shard02 { "estimate" :
false, "size" : 0, "numObjects" : 0 }
{ "n" : 0 } -->> { "n" : 1 } on : shard00 { "estimate" : false, "size" :
1224, "numObjects" : 34 }
{ "n" : 1 } -->> { "n" : 2 } on : shard01 { "estimate" : false, "size" :
1188, "numObjects" : 33 }
{ "n" : 2 } -->> { "n" : { $maxKey : 1 } } on : shard02 { "estimate" :
false, "size" : 1188, "numObjects" : 33 }

54. ➜ ~ mongo localhost:27017
> db.myshard.count()
34
> db.myshard.distinct("n")
[ 0 ]
➜ ~ mongo localhost:27018
> db.myshard.count()
33
> db.myshard.distinct("n")
[ 1 ]
➜ ~ mongo localhost:27019
> db.myshard.count()
33
> db.myshard.distinct("n")
[ 2 ]

57. > db.adminCommand( { addshard: "set00/delta1:27017,delta2:27017", name:
"shard00" } )
{ "shardAdded" : "shard00", "ok" : 1 }
> db.adminCommand( { addshard: "set01/delta3:27018,delta4:27018", name:
"shard01" } )
{ "shardAdded" : "shard01", "ok" : 1 }
> db.adminCommand( { addshard: "set02/delta5:27019,delta6:27019", name:
"shard02" } )
{ "shardAdded" : "shard02", "ok" : 1 }

64. Map-Reduce on Mongo

67. db.mycoll.mapReduce(
map : <map >,
reduce : <reduce >
[, finalize : <finalize >]
[, query : < >]
[, sort : <
reduce >]
[, out : < >]
[, scope : <object where fields go into javascript global scope >]
);

68. db.people.insert({userId:1, age:24, type:"A"})
db.people.insert({userId:2, age:47, type:"B"})
db.people.insert({userId:3, age:34, type:"C"})
db.people.insert({userId:4, age:4, type:"B"})
db.people.insert({userId:5, age:14, type:"A"})
db.people.insert({userId:6, age:29, type:"C"})
db.people.insert({userId:7, age:39, type:"C"})
db.people.insert({userId:8, age:42, type:"B"})
db.people.insert({userId:9, age:56, type:"A"})
db.people.insert({userId:10, age:12, type:"A"})

69. m = function() {
emit(this.type, { age: this.age, num: 1 } );
}

70. r = function(key, values) {
var result = { age: 0, num: 0 };
values.forEach( function(value){
result.age += value.age; // age
result.num += value.num; //
} );
return result;
}

71. r = function(key, values) {
var num = 0;
var sum = 0;
values.forEach( function(value){
sum += value.age; // age
num += value.num; //
} );
return sum/num;
}

72. m = function() {
emit(this.type, { age: this.age, num: 1 } );
}
r = function(key, values) {
var result = { age: 0, num: 0 };
values.forEach( function(value){
result.age += value.age; // age
result.num += value.num; //
} );
return result;
}

73. m = function() {
emit(this.type, { age: this.age, num: 1 } );
}
r = function(key, values) {
var result = { age: 0, num: 0 };
values.forEach( function(value){
result.age += value.age; //
result.num += value.num; //
} );
return result;
}

74. f = function( key, result ){
result.avg = result.age / result.num;
return result;
}

75. > res = db.people.mapReduce( m , r ,
{ finalize : f , out : "mr_out", verbose: true });
{
"result" : "mr_out", //
"timeMillis" : 18, //
"timing" : {
"mapTime" : NumberLong(1),
"emitLoop" : 12,
"total" : 18
},
"counts" : {
"input" : 10, // 10
"emit" : 10, // 10 emit
"output" : 3 // 3
},
"ok" : 1,
}

76. > db.mr_out.find()
{ "_id" : "A",
"value" : { "age" : 106, "num" : 4, "avg" : 26.5 } }
{ "_id" : "B",
"value" : { "age" : 93, "num" : 3, "avg" : 31 } }
{ "_id" : "C",
"value" : { "age" : 102, "num" : 3, "avg" : 34 } }

77. > res = db.people.mapReduce( m , r ,
{ finalize : f , out : "mr_out", query: { age: { $gte: 20 } } });
{
"result" : "mr_out",
"timeMillis" : 35,
"counts" : {
"input" : 7, // 3
"emit" : 7,
"output" : 3
},
"ok" : 1,
}

78. > db.mr_out.find() //
{ "_id" : "A",
"value" : { "age" : 80, "num" : 2, "avg" : 40 } }
{ "_id" : "B",
"value" : { "age" : 89, "num" : 2, "avg" : 44.5 } }
{ "_id" : "C",
"value" : { "age" : 102, "num" : 3, "avg" : 34 } }

81. db.items.insert({ date: "2011-06-01", item: "apple", price: 100 })
db.items.insert({ date: "2011-06-01", item: "banana", price: 200 })
db.items.insert({ date: "2011-06-01", item: "apple" , price :100})
db.items.insert({ date: "2011-06-02", item: "orange", price: 50 })
db.items.insert({ date: "2011-06-02", item: "orange", price: 50 })
db.items.insert({ date: "2011-06-02", item: "apple", price: 100 })

82. m = function() { emit(this.item, this.price); }
r = function(key,values) {
var result = 0;
values.forEach( function(value){ result += value } );
return result;
}
> res = db.items.mapReduce( m, r, { query: {date: "2011-06-01"} ,
out: {replace: "mr_out2"}} );
{
"result" : "mr_out2",
"timeMillis" : 10,
"counts" : {
"input" : 3,
"emit" : 3,
"output" : 2
},
"ok" : 1,
}
>db.mr_out2.find()
{ "_id" : "apple", "value" : 200 }
{ "_id" : "banana", "value" : 200 }

83. > res = db.items.mapReduce( m, r,
{ query: {date: "2011-06-02"} , out: {reduce: "mr_out2"}} );
{
"result" : "mr_out2",
"timeMillis" : 23,
"counts" : {
"input" : 3,
"emit" : 3,
"output" : 3
},
"ok" : 1,
}
> db.mr_out2.find()
{ "_id" : "apple", "value" : 300 } //
{ "_id" : "banana", "value" : 200 } //
{ "_id" : "orange", "value" : 100 } //