1. base de dados orientada a
documentos para aplicações Web
Kristina Chodorow

2. Who am I?
Software Engineer at
Here from New York City

3. Why Use
Non-Relational DBs?

6. CAP
• Consistency
nome : "joe" nome : "joe"
• Availability
• Partitioning

7. Key-Value Stores
Key Value
foo bar
x 123
ts 6:13:26 12/3/1945
data x9Fx44x1e
Tokyo Cabinet, Dynamo, MemcacheDB

8. Key-Value Stores
•Fast •Too simple
•Simple

9. Column-Oriented
Cassandra

10. Document-Oriented
{
date : Date(2007-05-07),
time : {
start : 9.25,
end : 10.25
}
sum : 0,
comments : ["task 1", "run 4", "testing module"]
}
vs.

11. Consistency
Availability
Partitioning

12. Consistency
Availability master
Partitioning
slave

13. Consistency
Availability
Partitioning
slave

14. Consistency
Availability
Partitioning
master

15. Consistency
Availability slave
Partitioning
master

16. Consistency
Availability
Partitioning Pair
Router
Pair
Pair
...eventual consistency

19. Introduction to MongoDB

20. A JavaScript Database
$ mongodb-linux-1.0/bin/mongo
MongoDB shell version: 1.0.0
url: test
connecting to: test
type "help" for help
>

21. JSON and BSON
Strict JSON types:
{
x : null, y : true, z : 123, w : "xyz",
a : { b : 1 }, c : [1, 2, 3]
}
Mongo JSON adds:
{
ts : new Date(),
query : /regex/ig,
_id : new ObjectId()
}

22. Collections, not Tables

23. Collections
{
date : Date(2007-05-07),
time : {
start : 9.25,
end : 10.25
}
sum : 0,
comments : ["task 1", "run 4"]
}

24. Using the Shell
> db
test
> use xyz
> db
xyz
> db.splorch.find()
>

25. Inserting
> db.foo.insert({name : "Joe", age : 34})
> db.foo.find({name : "Joe"})
{
"_id" :
ObjectId("2fe3e4d892aa73234c910bed"),
"name" : "Joe",
"age" : 34
}

26. Object Ids
an autogenerated primary key
"_id" : ObjectId("2fe3e4d892aa73234c910bed")
12 bytes:
2fe3e4d892aa73234c910bed
|------||----||--||----|
ts mac pid inc

27. Nested Objects
> db.blog.insert({title : "First Post",
content : "Hello, world!",
author : {name : "Joe", id : 123},
comments : []
})

28. Querying
posts = db.blog.find({
"author" : "Joe"})
commentsByFred = db.blog.find({
"comments.author" : "Fred"})
commentedByFred = db.blog.find({
"comments.author" : /fred/i})

29. Speaking of indexing…
db.people.ensureIndex({"age" : 1});
db.people.ensureIndex({
"name" : -1,
"ts" : -1,
"comments.author" : 1
});

30. Updating
db.blog.update({title : "First Post"}, {
$push : {
comments : {
author : "Fred",
comment : "Dumb post."
}
}
});

31. …which gives us:
> db.blog.findOne()
{
_id : ObjectId("4ae06192213900000000745c"),
"title" : "First Post",
"content" : "Hello, world!"
"author" : {"name" : "Joe", "id" : 123}
"comments" : [{
"author" : "Fred",
"comment" : "Dumb post"
}]
}

32. $ instead of >, <, =, etc.
$gt, $gte, $lt, $lte, $eq, $neq, $exists,
$set, $mod, $where, $in, $nin, $inc
$push, $pull, $pop, $pushAll, $popAll
db.foo.bar.find({x : {$gt : 4}})

33. $where
db.blog.findOne({$where :
'this.y == (this.x + this.z)'});
Will work:
{"x" : 1, "y" : 4, "z" : 3}
{"x" : "hi", "y" : "hibye", "z" : "bye"}
Won’t work:
{"x" : 1, "y" : 1}

34. Optimizing $where
db.blogs.findOne({
name : "Sally",
age : {'$gt' : 18},
$where : 'Array.sort(this.interests)[2]
== "volleyball"'});

35. Cursors
cursor = db.blah.find(array("foo" : "bar"))
while (cursor.hasNext()) {
obj = cursor.next()
}

36. Applications

37. soliMAP
@trackmeet
FetLife
Dextify2

38. Paging
cursor = db.results.find()
.sort({"ts" : -1})
.skip(page_num * results_per_page)
.limit(results_per_page);

39. Logging
• insert/update/remove is fast
• Capped collections
• Schemaless
• $inc for counts

40. Storing Files
Max: 4Mb

41. Storing Files
(More than 4 Mb)

42. Storing Files
J J J
chunks
J J J
J J J _id : J files

43. Storing Files
ObjectId fileId = new ObjectId();
fileObj = {
_id : fileId,
filename : "ggbridge.png",
user : "joe",
takenIn : "San Francisco"
}
chunkObj = {
fileId : fileId,
chunkNum : N
data : <binary data>
}

44. Aggregation
group =~ GROUP BY
Map/Reduce
db.runCommand({
mapreduce : <collection>,
map : <mapfunction>,
reduce : <reducefunction>
[, query : <query filter object>]
[, out : <outputcollectionname>]
[, keeptemp: <true|false>]
[, finalize : <finalizefunction>]
})

45. www.mongodb.org

46. Drivers
C#, Erlang, Factor

47. Thank you!
kristina@10gen.com
@kchodorow
@mongodb
irc.freenode.net#mongodb
www.mongodb.org