Map/reduce, geospatial indexing, and other cool features (Kristina Chodorow)

MapReduce, Geospatial Indexes,
and Other Cool Features

Kristina Chodorow

connecting to
your mongod

connecting to
your mongod

you

connecting to
your mongod

you

mongod

update insert query insert query mongod

query

insert

driver

insert

query mongod

driver

insert
getlasterror

mongod

driver

insert
getlasterror
mongod

driver

replication
Dwight @ 3:15
Farallon Room

make sure two
slaves have this

> db.runCommand({
... getlasterror : 1
... })

> db.runCommand({
... getlasterror : 1,
... w : 3
... })

> db.runCommand({
... w : 500
... })

> db.runCommand({
... w : 500,
... wtimeout : 3000
... })

> db.runCommand({
... fsync : true
... })

Operations:
insert
update
remove
query
get more

$ mongo
MongoDB shell version 1.5.1
url: test
connecting to: test
type "help" for help
>

> db.help()
DB methods:
db.addUser()
db.auth()
db.cloneDatabase()
db.commandHelp()
db.copyDatabase()
db.createCollection()
db.currentOp()
...

> db.foo.help()
DBCollection help
db.foo.count()
db.foo.dataSize()
db.foo.distinct()
db.foo.drop()
db.foo.dropIndex()
db.foo.dropIndexes()
...

> var cursor = db.foo.find()
> cursor.help()
DBQuery help
.sort()
.limit()
.skip()
.count()
.size()
...

http://api.mongodb.org/js

> db.foo.count()
40
> db.foo.count

> db.foo.count()
40
> db.foo.count
function(x) {
return this.find(x).count();;
}
>

> db.foo.count()
40
> db.foo.count
function(x) {
}
>

> db.foo.count()
40
> db.foo.count
function(x) {
}
> cursor.count

> cursor.count
function(applySkipLimit) {
var cmd = {count : this._collection.getName()};;
if (this._query) {
if (this._special) {
cmd.query = this._query.query;;
}
else {
cmd.query = this._query;;
}
}
cmd.fields = this._fields || {};;
if (applySkipLimit) {
if (this._limit) {
cmd.limit = this._limit;;
...

function(x) {
// prep cmd
...

// run command
var res = this._db.runCommand(cmd);;

// return result
...
}

> db.runCommand({count : "foo"})
{
"n" : 40,
"ok" : 1
}
>

> db.runCommand({listCommands : 1})

> db.runCommand({listCommands : 1})
{
"commands" : {
"$eval" : {...},
"assertinfo : {...},
"authenticate" : {...},
"buildinfo" : {...},
"clean" : {...},
"clone" : {...},
"cloneCollection" : {...},
"cloneCollectionAsCapped" : {...},
"closeAllDatabases" : {...},
...

> db.runCommand({
... datasize : collectionName})

> db.runCommand({
... datasize : collectionName})

> db.runCommand({
... dbstats : 1})

> db.commandHelp("distinct")
help for: distinct: {
distinct : 'collection name',
key : 'a.b' }
>

> db.commandHelp("distinct")
help for: distinct: {
distinct : 'collection name',
key : 'a.b' }
> db.commandHelp
function(name) {
var c = {};;
c[name] = 1;;
c.help = true;;
return this.runCommand(c).help;;
}
>

> db.runCommand({"count" : 1,
... "help" : true})

> db.runCommand({"count" : 1,
... "help" : true})
help for: count: no help defined
>

> db.blog.posts.find(
... {_id : 123},
... {comments : 1})

... {_id : 123},
... {comments : {$slice : 10}})

... {_id : 123},
... {comments : {$slice : [20, 10]}})

... {_id : 123},
... {comments : {$slice : -10}})

... {_id : 123},
... {comments : {$slice : [-20, 10]}})

> db.blog.posts.find({
... comments : {
... date : {$gt : today},
... votes : {$gte : 10}
... }})

... 'comments.date' : {$gt : today},
... 'comments.votes' : {$gte : 10}
... })

... comments : {$elemMatch : {
... date : {$gt : today},
... votes : {$gte : 10}
... }}})

{
_id : 123,
name : "Fred",
email : "fred@example.com"
}

{
_id : 456,
name : "Paul",
phone : "555-5555",
picture : BinData
}

{
_id : 789,
email : "alice@example.com",
}

_id 40
name 32
email 20
phone 2
picture 17
pet 3
friends 40
hobbies 6
favorites 12
notes 14

{
_id : 123,
name : "Fred",
email : "fred@example.com"
}

_id
1

name
1

email
1

map = function() {
for (var key in this) {
emit(key, 1);;
}
}

reduce = function(prev, current) {
var count = 0;;
for (var egg in current) {
count += current[egg];;
}
return count;;
}

A B C D E F

_id : A, value : _id : C, value : _id : E, value :

_id : B, value : _id : D, value : _id : F, value :

> db.users.find({
... date : new Date("10/3/2010")})

> db.users.ensureIndex({
... date : 1})

Dates, timestamps, ObjectIds

indexing
Aaron @ 3:15
Niantic Room

> db.map.ensureIndex({location : "2d"})
>

> db.map.insert({location : [-40, 78]})
>

> db.map.insert({location : {
... x : -40,
... y : 78}})
>

... x : -40,
... y : 78}})
... longitude : -40,
... latitude : 78}})
>

> db.map.find({location : {
... $near : [-40, 77]}})

> db.map.find({location : {
... $near : [-40, 77]}})->limit(10)

> db.map.ensureIndex({
... location : "2d",
... user : 1});;

1 degree of longitude at the equator:

1 degree of longitude at the equator:

1 degree of longitude near the poles:

geospatial
Eliot @ 10:15
Gateway Room

please help
document stuff!

http://cookbook.mongodb.org

want to work on
mongodb?

http://www.10gen.com/jobs

thank you!

@kchodorow

http://www.snailinaturtleneck.com

Map/reduce, geospatial indexing, and other cool features (Kristina Chodorow)

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Map/reduce, geospatial indexing, and other cool features (Kristina Chodorow)